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Winter Project! BBS02 DIY Build


10 mW
Dec 12, 2016
suburbs of St. Paul, Minnesota
I've been doing a lot of research for a winter e-bike build and thought I'd lay out my thoughts here to share my reasoning for others who are considering a build and to get some feedback from others more experienced. I've certainly benefitted from what others have posted and it's time to share. I primarily use my bike to commute to work, 5 miles each way, but also use it to run errands and get around the suburbs and into the city.

I purchased a Marin Muirwoods to use as a donor bike. It's a 4130 CrMo steel self-described "rough and tumble commute machine" with Tektro Auriga hydraulic disc brakes and a 9-speed Shimano Alivio rear derailleur. Weighs about 28 pounds. Got lucky and saw it brand new on deep discount (LT $500 tax included) at a LBS a few weeks ago. The 68mm bottom bracket is ideal.
Muirwoods (Custom).jpg

I'm planning to add a BBS02 mid-drive over the winter. Luna is my winner for the kit. Here's my order from Luna that I placed a few days ago:
  • Bafang BBS02 750w Mid Drive eBike KIT (Sprocket Size: 48T, Full Color Display, Bafang BBSxx Universal Thumb Throttle, Magnetic sensors to use your own brake levers, Bafang Programming Cable, Mighty Mini 52v GA, 52V Advanced 300W Ebike Charger
  • Luna Cycle Mighty Mini Battery Pack Seat Case
  • LUNA Wrench BBSHD and BBS02 Mid Drive Installation Tool
  • $1050 including shipping

Here are some thoughts I went through in researching and thinking this out.

Hub vs Mid
I started out like many thinking a simple 250w hub kit was all I wanted. Just travel my 5 mile commute to work and be a little less sweaty. I was interested in the 250w hub motor partly because it's such a stealth approach but also because I felt I could fairly easily add it and remove it from my bike: one bike to rule them all! Another dream was to be able to install it on other bikes to share the electric experience with others on group rides while I pedal along with them w/ no assist. I was thinking about a super-simple kit that had the hub motor, battery, and on-off switch on the handlebar. At 150 pounds, I'm light and I'm willing to pedal along so I still feel this would have been reasonable. But as I read more and more (and started travelling greater distances on my bike) I came to the conclusion I wanted more speed and power. I researched the hotrodding path but came to the conclusion I'd fry a 250w hub motor. Then I started looking at more powerful hub motors but they were bigger and more obvious. And heavy. I had frequently come across the bbs02 in my research but blew it off for months because "I didn't want a mid-drive". Then one day something just clicked and I started giving the bbs02 more consideration. It's fairly stealthy with its mounting point below the bottom bracket. Check. The controller is integrated so I don't have to carry another brick. Check. I can tweak the programming. Check. It mounts about as low as you could mount a motor which is great for weight distribution. Check. I had to give up the dream of easily moving it from bike to bike. Okay, don't like but let's keep talking. In exchange I get to use the rear derailleur as a transmission. Bonus! 25+mph. Bonus! Hmmmm….yes, this is for me. Mid drive it is.

Prebuilt vs DIY
A lot of really cool prebuilt ebikes exist. It would have been an easy choice that would have gotten me into an e-bike much faster and with LBS support. I went to a LBS and tried a Trek. It was fun but it just didn't feel right to cut out at 20mph, I can pedal that fast and I knew I wanted the ability to go faster. I just didn’t feel it was worth the sticker price. A different Trek that does 28mph is close to $3,000. With DIY, I like the idea of being able to tweak the programming. I live in the suburbs and when I commute to work I'm frequently the only bike I see -- I'm not going to bother anyone going 25mph on the side of a 55mph highway. Plus I'm making a small hobby out of this DIY project, I like the lower cost, and have enjoyed learning more about wrenching, motors, controllers, and batteries.

Steel vs Aluminum
Steel won for me. I just didn’t feel comfortable with aluminum knowing the BBS02 bites into the bottom bracket to help it stay put. I also like the softer feel of the ride and it's such a reliable and dependable material. It appears many people have had successful builds on aluminum and Luna is using them on their own builds which I'm sure they stand behind but the aluminum bikes I was looking at were 25 pounds themselves, upwards of 30 with a front suspension and with the Muirwoods donor bike coming in at 28 pounds, just three more than the comparable aluminum models, I felt more comfortable with steel.

Other bikes I considered:
  • Trek 750 Multitrack (steel, used, rim brakes)
  • Trek Zektor 2 (aluminum commuter w/ disc brakes)
  • Trek DS2 (aluminum, disc brakes, front shock)
  • Norco Indie (aluminum, disc)
  • Novara Buzz (aluminum, disc)
  • Cannondale Bad Boy (aluminum, disc)
  • Fuji Police Bike (aluminum, disc brakes, front shock, 26" wheels)
  • Luna makes a fully assembled e-bike out of the KHS Police Bike

The Muirwoods was also an interesting combination of lower-end Altus front derailleur (which I didn't care about because it'll be removed) and the next level up rear derailleur from the Alivio line. At least I didn't pay a premium for a front transmission I won't be using.

Disc vs Rim Brakes
I bike in all types of weather and with the increased speed I wanted disc brakes for consistent performance regardless of conditions. I wound up with hydraulic but feel like I could have been just as happy with cables, and maybe even happier, because mounting e-brake cutoff sensors appears to be a challenge because of the way the hydraulic levers work. I'm sure I'll have to tinker with this a bit.

Suspension or No
I went without. I currently commute on a Masi CX cyclocross bike with 700x28c tires. It's a steel frame with no suspension. I travel up to 30mph on the big downhill portion of my commute with no issues or complaints. I have no problem lifting off the seat to avoid bumps and potholes. The Marin donor bike has 700x40c tires which should provide additional cushion from where I'm at now with 28c. For me the front shock just seemed like extra complexity and weight I didn’t need. I'm not planning to ride singletrack or do any substantial off-roading. In short, I plan to ride this like a bike, not sit on it like a motorcycle, so I feel comfortable I'll be fine w/o a suspension.

Gear Ratio/Inches and Wheel Size
I wanted a wide range back cassette to be able to control the load on the motor to prevent overheating on hills and to be able to go fast on the flats. I wound up with a 12-36 cassette in the rear. Perfect. The existing front chainring is 48/36/26. Since I've already got a 48t in the front I got the 48t Bafang chainring and I think this will work great with the 12-36 in the rear. The front-back 48-12 gearing paired with 700x40c wheels should provide a very reasonable cadence of 77rpm at 25mph. Calculate your cadence at speed.

Flat or drop bars
Went with flat mainly for safety. I can be upright riding in traffic with good vision and I can keep my hands right on the brakes where I've got options for emergency stopping/skidding. I might add bar ends for some additional riding positions when not in traffic and for use when out of the saddle.

I ditched the hub motor but I'm still wanting to make this build as stealthy as possible. I'd prefer not to have a shark pack or bottle mounted in the triangle. I might regret not having the battery locked to the frame but I don't think I'd be able to trust the lock. How do others feel? In what conditions do you leave your $500 shark pack locked to your frame when you lock up your bike? I went with Luna's mighty mini, the 52v x 7Ah version with the GA cells. Sure, it's got limited range, but it would easily get me to work and back (10 mile RT). I thought I'd start with one and maybe work my way into another to extend my range. This battery is small. It would easily fit in my saddlebags, in Luna's seat bag (which I purchased), in a third party seat bag like this, maybe on my rear rack with a custom mount, or possibly I could make something to store it inside the main triangle using the two sets of bottle cage bosses on my frame. It's 6x2.75x3.25 inches -- that's pretty stealth. At 3.3 pounds it's light enough and small enough to carry along with you. At 110Wh/pound it's the most dense battery I've found. I wanted to get a feel for exactly what it would be like so I made a scale model by cutting up and re-gluing a cracker box and filling it with some padding and coins to 3.3 pounds. I know, #geekalert, but it's really given me a good idea of what it would be like.

Tools I already own

Tools and supplies I bought specifically for the build
TIP: If you don't know much about removing cranks or bottom brackets this video from Park Tool cleared it up for me.

Here's a picture of some of the tools and supplies.
Tools (Custom).jpg

Still need
  • C-spanner tool and bottom bracket cup wrench. I bought the Luna wrench which does both.
  • (Might need/want) Moldable rubber like Sugru or Versimold. This could be useful for mounting the brake sensors or providing some cushion for the battery.
  • I may need a small grindstone for an electric drill as there may be tiny bits of weld inside the BB. Or a Dremel. I'm hoping I don't need this and my BBS02 will just slide right in.

Something you might need that I don’t
  • Chain breaker if your chain doesn't have a missing link and you want to remove your front derailleur you'll need to break your chain. My chain has a missing link -- there's a tool for that too but it can be done by hand or I've seen some hacks using a wire. I'll take my chances on this and if I have trouble I may need to get a special pliers-like tool to get the missing link apart. Here is a good video that explains a lot about chains.

My background
This section I'm writing just to give other noob builders out there some idea of my background as I embark on this project. I've read a few posts from people that felt they were fooled into taking on a bigger project than they could handle after hearing that a DIY e-bike build is "easy". My hope is that this will help you calibrate your own chance for success as I go through my own build. Here goes:
  • I've done basic bike maintenance like changing tires and adjusting brakes.
  • I recently assembled a brand new single speed bike shipped to my house in a box.
  • I've never pulled off cranks or a bottom bracket.
  • I own a home and do much of the maintenance myself. I change out the mower deck and snowblower every year on my tractor. I've done some small remodeling projects like finishing a roughed-in bathroom but that was near the limit of my desires, abilities, and tools. I've dabbled in woodworking and have power saws, drills, and sanders.
  • After reading and watching a ton of material over the last few months, with the set of tools I own, and the few purchases I've made, I'm feeling prepared to get going on the build.
  • In summary, a mid-drive install is not something you do at home with "mother's toolbox". You need some special tools and knowledge. But it is within the reach of mortals -- you don't need to be a mechanic to do this. Or so I think. Time will tell. ;)

Finally, I just got word that my motor and battery have shipped! I've got to get going on the bike prep. I'm hoping to make a couple updates about that and then it will be on to the BBS02 install itself. Cheers. :)
Good analysis - couple of things to consider down the track noting you've already picked up on a bigger battery as you start to increase the distances/speeds you ride.

Suspension seat post like a thudbuster - on bbs bikes you don't spend much time out of the saddle and end up riding them a bit like a motorbike with less weights on your hands, more on your butt.

Lekkie bling ring - I have a spider to get a better chain line but will be going lekkie next.

Welcome to the world of bbs mid-drives !
Thanks for the replies.

@Tats, the existence of the suspension seat post is another reason I felt comfortable going without the front suspension. It's an easy add-on if I do find i need some shock aborption. With the Lekkie I'd have to go from a 48 tooth chainring to 42. That would change my gearing pretty substantially but it'd be worth it if I have a lot of chain drops on the stock set up. I took some before pictures of my chainline and will post some after the install.

@docw009, thanks for the vote of confidence. I hope you are right, I'm feeling prepared for this.

@drew12345, I just stumbled across the saddle bag for the MM in the last week. It's made with a water resistant material and the price is pretty good. It looks like they maybe even throw one in for free if you buy a MM ala carte.
Bike Prep Stage 1 -- Fenders, Rack, Remove Front Derailleur

Today I installed anAxiom Journey Rack, a set of Planet Bike Cascadia Fenders, and removed the front derailleur.

Installs for rack and fenders were easy. I had the rack already and I was pleasantly surprised to find it fit even with the disc brakes -- it's not a disc brake specific model but it was no problem at all. The fenders took some tinkering to get them to sit straight but all the spacers and long bolts I needed were supplied in the kit. Planet Bike provides a ton of extra hardware options like spacers and 45mm bolts. Here are links to pictures of the 2 instruction pages page1, page2 -- they have a complete parts inventory. Tire clearance on the back fender is a little tight mainly because I have the rack tilted back a bit -- I'm thinking about mounting my Mighty Mini battery between the rack and the seatpost/downtube rather than suspending it from the seat. With my life size model of the battery I built I can see that I'll have just enough room. We'll see how it works when the battery arrives.

Removing the front derailleur was pleasantly easy. No glitches. To break the chain I simply took the two ends of the magic link and, with my hands, pushed them together and voila, it snapped open. Here's a picture of the magic link after it had been separated.

Then I detached the cable, removed the derailleur mounting screw and, with the chain out of the way, the derailleur came off. I pulled off the handlebar grip with nothing more than slow steady pressure, no soap or anything. Then it was just a matter of loosening the brake lever and removing it so I could loosen the shifter and remove it. Really very simple and no surprises.

This is going better than expected. Hopefully it stays that way.

Fenders on, rack on, front derailleur off.

The Muirwoods donor bike has ample braze-ons and mounting points for the accessories. The back, where both the fender and rack attach, has two mounts so I didn't need to double anything up.

View from the drivetrain side
Great looking bike. Nice photos so far, always fun to see someone else's project progressing. Looking forward to seeing how it goes.
Bike Prep Stage 2 -- Clear the Bottom Bracket

I wanted to clear the underside of the bottom bracket for the motor. The cable for the rear derailleur was routed underneath the bottom bracket but veered substantially away from the down tube. I would guess about 5mm. If I left it like this I would have had to tilt the mid drive away from the down tube 5mm or more to avoid the cable and I wanted to have the motor tilted up as far as possible for clearance. This might have been overkill but I wanted to try to clear under the BB.

Here's how it looked when I bought the bike. Left to right is the rear hydraulic brake line, the front, and then the rear derailleur cables.

In this picture you can see how far the rear derailleur cable is away from the down tube.

Side angle:

In the picture below I've already removed the front derailleur and you see the brake line, rear derailleur cable, and cable guide.

Last picture before any changes. Here's how it originally finished off at the derailleur.

The solution was to buy ~5 feet of cable housing to make the entire trip from the shifter to the rear derailleur. Jason at The Hub Bike Co-op in Minneapolis was nice enough to measure out the correct length for me and he even threw in a couple metal end caps. Installation was pretty simple. I took the terminal cap off the end of the existing cable and pulled it through all the way up to the shifter removing the two existing housing segments. I then routed the cable through my new housing and reattached at the derailleur. A few strategic zip ties hold the new housing in place and I'm all set.

Prior to starting, it helped to shift into the highest gear in the rear (smallest sprocket) and then take tension off the derailleur and cable before detaching the cable -- I used a small piece of wire to pull the derailleur toward the pedal, one of the above pictures shows this.

After reassembly I thought I might have shifting issues but I had very little. I just used a couple turns of a micro adjuster and shifting is working well again.

The new housing consumed about an inch or two more cable than the previous run. I could have shortened the new housing but I still had enough cable to clamp at the derailleur. I just have less hanging out after the clamp.

The last thing was to remove the now unused plastic cable guide from the bottom bracket. I now have a clean bottom bracket just waiting for the mid drive to show up. If you look closely at the picture below you can see the new housing for the rear derailleur cable on the right of the downtube. I might move the brake line above the BB when the cranks come off but I'll wait until the motor arrives and see how it looks -- it might be fine right where it is.

Question: what should I do with the hole in the BB where the screw is? That's as far as the screw will go in. I assume the BBS02 will fill up the full diameter of the BB so the screw will look the same when I get it installed. Just leave it as-is? Get a shorter screw? Should I try to seal it somehow, with something like silicone, or is that just asking for trouble? A shorter screw and some grease? Suggestions?
Kit Arrived!

Kit looks great! Luna shipped my kit within a few days of placing the order. The delivery takes a bit longer than you might expect because the battery requires all-ground travel on UPS. All arrived in good shape but I did have a few surprises:
  1. The battery had an Anderson connector rather than the XT90-S I expected. I filed a support ticket with Luna and after a few exchanges where we considered if I should switch out the connector myself (it's a bit dangerous) we decided it's best to return the battery and let them ship out the correct one. They simply shipped the wrong one. They hinted the one I got was an oddball meant for a different customer. Even dealing with a US-based vendor the shipping is still expensive in the $40-50 range because the battery has sufficient capacity to be considered hazmat. Luna was great and honored their mistake by paying shipping both ways to get me the correct battery. I hate to imagine what it would be like dealing with a Chinese company. Kudos to Luna.
  2. The motor came with the Bafang stock bullet connectors for connecting the battery. For some reason I expected Luna would ship the motor with a pre-installed an XT90-S connector. In hindsight this is just something I missed. Not a big deal, I just need to solder in the new connector when it arrives with the new battery. But I'll suggest to Luna that they should sell "kits" whose electric components work together without this extra step. It would be simple enough for them and it would make installing the kit just that much easier for DIY'ers. Maybe add it as an extra add-on for a small fee?
  3. With the confusion on the battery I got a bunch of extra connectors and things I don't think I need. I asked Luna about it and they said just keep it.
Just one other comment about the shipment. It was sent UPS with signature required. For me it was easiest to ask UPS to route it to the nearest UPS store which worked out great. I have a UPS account but I think you can do this with nothing more than the tracking number.

Here's a picture of the full kit that I received.

Here's a close up of the motor. You can see the bullet connectors. I've got to practice my soldering a bit as I'll need to solder on a new XT90-S connector.

And this is a picture of the battery connectors on the battery I received initially. The red/black is an Anderson connector. I was expecting the XT90-S for its anti-spark system which you can see demonstrated in this video.


So I've had a little delay but things are progressing. In the meantime I can get started on a few things like mounting the
display and throttle. I can also pull the cranks and remove the cartridge from the bottom bracket.
Bottom Bracket Open, New Battery Arrived

Pulling cranks and removing the bottom bracket cartridge was a breeze. I had the right tools and it's a new bike so things came apart just as expected. Here's some bottom bracket art. I might have to make this my avatar for the forum.

I'm thinking I'll do a future post with more about component weights. But for now let me just say that I've pulled 4.7 pounds of equipment off the bike at this point. That's made up of cranks, chainrings, bottom bracket cartridge, front derailleur, front shifter, stock rear derailleur cable housing, the small plastic cable guide that was under the BB, and the stock pedals because I got some replacements that take the pedal straps that I like. Added on so far are the new housing for the rear derailleur cable, the rack, and fenders. With the empty bottom bracket, fenders, and rack I just weighed the bike and I'm right back at 28 lbs. If I tally everything else I'm adding I'm figuring on being just shy of 44 lbs including battery. Not too bad and right in line with what I expected.

Speaking of battery, the new one arrived and has the XT90S-S connector. Awesome. However, I was surprised to find it has a voltage meter. Maybe one of the pictures on the website has a hint of it, but there's a clear picture of one without. Maybe they've always had it and it's not clear on the web site. At any rate, it's an interesting addition to a battery that prides itself on being small and light. The meter is probably part of what makes the battery a bit bigger than spec'd and a bit heavier. Mine came in at 3.7 pounds. Still light but significantly over the 3.3 lb advertised weight. I doubt the meter consists of the entire 0.4 lb difference from spec as the original one I was shipped weighed 3.5 lb and did not have a meter. The dimensions are also different than the spec on the website. 6 x 3.25 x 2.75 inches? Not exactly. Mine is 5.9 x 3.5 x 3.125. Not really significant, but different. Here's the kicker though. It's a really tight fit into the saddle bag I bought direct from Luna. The extra girth is significant when trying to tuck it into the bag. It does fit and I think I'll get more skilled at inserting and removing it as I do it more. So it's fine but it's kind of a pain and I feel like maybe the bag won't last as long because I kind of need to crank on it. If you ask me, I would trade the meter for the smaller size and weight savings. What good is a meter when it's tucked in a saddle bag most of the time anyway? I won't even be able to see it because it'll be in the front of the bag. Hmmm. Pffft. Just part of the fun of the DIY family I guess. :) Still, much better and safer than I could do myself and not a big deal. I’m getting really excited to get this thing assembled and running.

From looking at this picture of the XT90-S on the Hobby King site I thought the XT90-S came as a set with unique features on both the male and female side. However I was only shipped XT90 (no "s") to solder onto the controller. After some research I've come to the conclusion that one side does all the magic and using a normal XT90 on the other is fine. This thread helped: You only need the S on one side. Which side is it you ask? Male or female? Ha, that's been another small learning opportunity. It depends on if you are talking about the metal connectors or the plastic housing. The female side of the plastic housing has the metal male pins so the terms can get switched if you are not clear. It seems the standard is to talk about the metal fittings and not the plastic housing. Therefore, the female side (with the green) has the magic. I'm mating the female XT90-S (with the green) that came on the battery with a male XT90 (no "s"). If that's trouble, somebody let me know please.

Moving on, it's time to get soldering. I bought some rosin core solder to make sure I had a good quality solder as I had just a little from my original Weller kit purchased 10+ years ago. A few youtube videos later and I'm out to practice. I got pretty good. Here's one of the later and better products of my practice.

With practice out of the way it was time to get that XT90 onto the controller. For the most part it went smoothly. The tips of the XT90 pigtail had been, I think, tinned with some solder to prevent them from fraying. I wanted to mechanically join the wires first so I cut that off and stripped a little more housing. The motor I think is a 12 gauge stranded wire. The XT90 has a 10 gauge stranded but boy are the strands fine like thinner than a hair and probably 150 of 'em are need to bulk up to the 10 gauge size. It was a little touchy to deal with. I slipped on the heat shrink tubing first and then it took a little finagling to get the wires mechanically joined but I got it to a point where I was satisfied. Then I went at it to solder it together. I feel that with the super-thin strands it was harder than my practice wires to get the joint hot but I feel like I did okay. I'm sure I got solder into the majority of the joint but I also wound up with a pretty big knuckle. Maybe some flux would have helped. After it cooled I started wondering if my heat shrink was even going to make it over the knuckle. I stretched it a bit and added some dielectric grease and it slid over pretty easily. I did have one tiny strand from the XT90 wire that poked through the heat shrink. This could have been easily avoided if I had just done a final smoothing on the joint. It's a tiny hole. Overall, I'm pretty happy with it. Here's the finished product.

Next up is assembly. I'm past the most difficult parts. Shouldn't be long now.
Sounds like you like DIY.

I did a Luna BBS02 install a few days ago, using a bike I've had for years. I added the motor to accommodate wind and hills where I am spending the winter. I have two bikes with me, so motorizing one didn't leave me without a conventional bike.

I'm away from home, so I had access to limited tools. I had a local bike shop remove my lower bracket. They charged $15. I'm still smiling about that.

The install took about 5 hours. I used crimp connectors, instead of shoulder. I'll do the soldering when I get home.


I think you'll like the BBS02. I've only used assist levels 1-3 out of 5, so far. At those levels and a comfortable pedal cadence, mine cruises at around 20mph.
BBS02 Install

Motor and wiring installs went smoothly! I just took my time and didn't rush things. With the wiring and motor installed, I've taken it for a couple test runs of 2-8 miles and the performance is great and just what I expected. Wheeeeeeeeeeeeeeeee!!! :)






I did decide to move my hydraulic brake line above the bottom bracket as the fit was a little tight and it could simplify brake line maintenance in the future. You can see that in a couple of the pictures above.

The battery in the Luna bag fits snugly between my seat post and my rack. The Velcro on the Luna bike bag is just perfect for attaching to the rack's arms that reach from the rack to the seat stays. It's snug, stealthy, and firmly mounted although I did hear it jostling around a little bit over bumps. Long term I might need another velcro strap.



I'm going to wait for some final build pictures until after the brake sensors are installed but it's looking pretty boss!

About the only issue I had with the motor install was that the housing for my rear derailleur cable got pinched in between the motor and the chainstay when I initially tightened everything up. I thought for a minute that the motor was hitting the frame itself and I was a bit spooked that I'd need spacers or something on the drivetrain side however all I had to do was loosen it up a bit, push the housing above the chainstay and then crank it back down. Speaking of cranking, the Luna wrench was awesome; it's the right tool for the job. As others have commented it does take a little maneuvering when tightening the lockring because it only has 4 positions where you can mount the wrench so this limits your choices. In some orientations the chainstay is in the way, in others, the motor. The good news is that with only 4 choices, the best one is pretty easy to spot.

The only thing I haven't fully installed are the brake cutoffs. I've got them connected to the controller but the magnet is simply fixed to the sensor. They are going to take a little more dinking around. For my test rides I was okay with this set up because the motor will cut out when I stop pedaling and then I just need to be careful w/ the throttle.

On my test rides I had no chain drops. The chainring sits squarely in the middle of my 9-gear cassette and I used all 9 gears in my test runs with no problems although the chain was a little clickety-clacky (noisy) when shifted out to the extremes.

I'm in Minnesota and it was a cool day when I tested so I wasn't too worried about overheating. I shifted into my lowest gear and throttled all the way up the big hill in my neighborhood with no pedaling which is about 110 foot rise over half a mile. The display showed 13.5 mph the whole way up. This is exactly the speed reached when running on flat ground in that same gear so my takeaway is that the motor had no problem pushing the total ~200 lb payload up the hill. Not too surprising with a 48x36 gearing. With my bike and that gearing that's around 125 rpm. I've set the wheel size on the display to match my bike but I haven't done any calibrations on how accurate the mph reading is but I think it's in the ballpark. I'll also mention that right out of the box my throttle works in PAS setting zero because I know this has been an issue over the years.

I must have read about a few people complaining about responsiveness of PAS systems in the past because I knew it was something I wanted to check out. I found that one quarter turn of the cranks and the motor is on. Every time. Stop pedaling and the motor turns off very quickly, like maybe a half second response time. Every time. It is reliable and consistent. This is due in part to the programming settings that Luna sent with the controller. I'm completely satisfied with the responsiveness of the PAS.

Next up is the brake sensor install.
Installing the brake sensors

I was curious about how well the Bafang Hydraulic Brake Sensors would work and how easily they would mount onto my brake levers which are small and don’t have a ton of travel. I need to do some testing to see how much movement is needed to engage the sensor. The video referenced on the Luna site is accurate but simplistic and maybe a easiest-case example. The other link to a how-to-install article on their forum is thorough and has good advice. My case is similar to what's referenced in the forum article in that I have no perfect place to mount the sensor or the magnet. Looks like I'm into some kind of epoxy or glue.

Sounds like a great time to experiment with the Sugru I purchased. Sugru is a moldable glue that cures to rubber over 24 hours. It makes a strong bond with many materials and yet it won't stick to plastic wrap which allows you to use it in tight spaces. Pretty slick stuff. I'm imagining this will look very clean, much cleaner than epoxy, because you can work with the product for 30 minutes to shape, form, and smooth the edges. Another advantage Sugru has over epoxy is that it's easier to clean it all off and start over if you mess it up. Oh yeah, it comes in midnight black too. Perfect.

Let's see how this goes….

First, here are some pictures of how the sensors would mount on my brake levers. The first picture looks like a reasonable fit:

But as we take a different angle we can see a gap.

Here is a slightly different position closer to where I actually mounted it, but still a gap.

You can see the need for some type of glue or epoxy to fill the gap to make a good bond. Without it, because of the shape of the brake lever, just a minimum of the supplied adhesive would come into contact where I need to mount the sensor. Sugru seems like an ideal choice. I plan to strip off the provided mounting tape and go all-in with Sugru. I briefly considered ripping the plastic case off of the sensor and just mounting the now-much-smaller device completely enclosed in Sugru but decided against this approach. More on using Sugru later.

Next up was testing the sensitivity to get a feel for the positioning and consistency of the sensor. In all, I'm very impressed. The switch provides consistent on-off operation with a minimum of travel. If I set the magnet about 4mm away from the sensor I need only 1mm of additional separation to disengage the motor. Every time I let go of the brake lever, the motor turns back on. Nice. For my brake set up, the motor cuts out well before the brake pads are pressing down on my rotor. This is ideal as I'll be able to use just a touch of my break levers like a clutch to momentarily disengage the motor to avoid shifting under load. The length of motor shutoff I consider to be short. I think this is adjustable in the Bafang programming/setup but however it's set if I just tap the brake lever I get half a second of motor disengagement. If I hold the brake lever for a second or more and then release I get more like a full second delay before the motor comes back on. That's a pretty short motor shutoff. I think I'll have to experiment to get the right technique down when shifting. And if I'm still crunching gears when shifting I might want to monkey with the programming to extend the delay. But that's another day.

Here's a picture of my initial sensitivity testing where I used some vinyl tape to hold things in place. 4mm between the sensor and magnet was about right to have a very responsive lever for motor cutout with a consistent engagement of the motor when the brake lever was released.

To test the sensors I put the bike in the lowest gear (largest sprocket) and held the "-" (minus) button to engage walk-along mode with the back wheel suspended off the ground. This way I could test the sensor operation with the wheel spinning at a slow 1.2mph instead of 15+ mph that the throttle would have kicked in at.

This may be obvious but the orientation and position of the magnet in relation to the sensor makes a difference in how it operates. The magnet can be mounted in three planes and it can be moved in three dimensions closer or further from the sensor. In my case there only one orientation made much sense -- flat against the brake lever. You just have to experiment and see what works best for your situation. Just make sure to replicate exactly what you tested when you go for the install, especially if you are using glue or epoxy, and even more so if you are working with small tolerances.

Mid-process I got to thinking, hey, I'm working with a 1mm tolerance here and I know magnets are polarized with a positive and negative. Would it matter if I rotated the magnet? Would it change the sensitivity or operation in any way? Off I went with a sharpie to mark up the magnet and find out. I didn't find any difference. Unless you are trying to work with the smallest of margins I don't think this should be a concern.

Satisfied with the sensitivity it was time to get going on mounting these bad boys! To get a really good feel for what this process would be like with the Sugru I used some removable office putty to mock up the finished product. This gave me a good idea of how much Sugru I'd need to mount the magnet and the sensor. It turns out about 1 pack per brake lever does the trick.

Pictures with white office putty.


I've never used Sugru before so for some extra protection in case the Sugru bonds poorly I first wrapped some fishing line around the magnet and then left a bunch of extra. A small bit of the line will just get molded right in with the Sugru. Eventually I'll tie the loose ends to the brake lever and trim it down. It will hardly be noticeable. If the Sugru fails for whatever reason, I'll still have my magnet.


The process took some time but wasn't difficult. First, I cleaned everything up with rubbing alcohol to remove any dust, oils, or office putty residue. I removed the provided double-sided sticky tape from the sensors. For good measure I scratched up the bottom of the sensor to give the Sugru something better to latch onto. Then it was just a matter of opening the Sugru, breaking into two pieces and forming it around the gear and onto the brake levers. You could do this in as little as 5-10 minutes but if you want it to look nice several rounds of smoothing are required. A finger works great. Guitar picks in several differing thicknesses helped for tight spaces. Final smoothing is best with a thin layer of dishwashing liquid on your finger. All throughout the process I continued to test the levers to make sure things weren't moving as they cured. Overall the Sugru was great to work with giving plenty of time to shape, mold, and refine. Hopefully I got enough surface area to get a strong bond. The components are light so I'm hopeful it will be a good long-term and durable solution.

Here's a picture after the Sugru was installed but before it had cured. The orange vinyl tape is to keep things from moving around.

And here's how it looks after the Sugru has cured. From more than a few feet away it almost looks like a single component. I'm very happy with how this turned out.






Next up I'll get some pictures of the complete bike.
Full Build Pictures

And finally, some pictures of it all put together. I still might try to find a way to conceal the wiring a little better. All in all the bike looks just like what I had envisioned. It's very clean, stealthy, and hard to tell it's a ebike. I commuted to work last Friday (5 mi. each way) and performance was excellent, very quiet, super fun, and easy to ride. This is the coolest thing I've ever built. 8)








Nice bike, enjoy!
And nicely documented build.
Thanks particularly for documenting the Sugru / brake switch install.
Need to do similar in near future.
Sugru is wonderful stuff, just wish it was less expensive.
footloose said:
Nice bike, enjoy!
And nicely documented build.
Thanks particularly for documenting the Sugru / brake switch install.
Need to do similar in near future.
Sugru is wonderful stuff, just wish it was less expensive.

I used black Milliput epoxy putty bought on Amazon for less than £5 and it did a great job.

Great build by the way!

NickC said:
I used black Milliput epoxy putty bought on Amazon for less than £5 and it did a great job.
Thanks for the tip! Sugru is great, but jeez the price... 50 cents a gram or something like that.
My Delivered Luna Controller Programming

I finally hooked up my controller to the computer and thought I'd share the delivered settings from Luna. What I found is different than others have posted as recently as October 2016. From reading up a bit I'm going to need to tweak these a bit to get things working the way I want.

First, here are some notes I can share about hooking up the controller to the computer.
  • The battery needs to be plugged into motor; this was not obvious to me as I thought power might be supplied to the controller through the USB cable
  • Hook up the battery, yes, but make sure to turn the system off using the controls included with your display
  • Disconnect the green plug from the display
  • Connect the green plug from the display to the green plug on the USB cable (I got mine from Luna)
  • You'll need a USB serial CH340 driver CH341SER.EXE, refer to this or this.
  • You'll need software to read/write from/to the controller. I've read Bafang provides buggy software that you can get by some simple searching but it seems most people use one that was reverse engineered and then improved. Read up and download that here.
  • I needed "Resize Enable" software because, for some reason the window on the controller software (for the screen prints below) came up showing about 40% of the surface area of the window contents. To boot, the window was NOT resizable. I have used this "Resize Enable" software in the past and it allowed me to resize the window so I could see the full contents. Get the software here.
  • Then you plug in the USB cable to the computer and go to device manager to figure out the COM Port. Refer to this picture on this blog entry.
  • The rest of the process is pretty well described in this article.
  • And these two are good resources to read. Programming The BBS02 & BBSHD Without Frying Your Controller And Losing Your Sanity and BBSHD and BBS02 Configuration (Programming) Resources.

I think I'm really going to enjoy tweaking these settings to get the ride characteristics I'm looking for. Plus, I’m hooking my freakin' bike up to a computer! How cool is that!

And here were my delivered settings from Luna:


Ride Report

After a month or so of commuting here are my observations (other than this bike is freakin' awesome). :)

Quiet. The motor is almost silent. I rarely even hear it.

Power. I've got it configured to max out at about 750 watts peak (52v*15a) and I find it plenty powerful. At my max PAS level battery consumption is rapid and based on the power output I feel when riding I don’t think I need to increase that at all. 52v * 18a (936 watts) seems to be a common max recommendation but I don't even think I need to go there. Honestly, I'm not sure what other people are doing with max peak 1300 watts (52v*25a) that the BBS02 can supposedly handle. I guess if you have a lot of hills and a heavier payload that makes sense but I don't need that. 750 watt peak is fine for me (bike+me < 200 pounds). For battery conservation I typically ride in PAS 5 which is a good balance between speed and battery consumption. PAS 5 for me is about 40% of the 750 watt peak. I can maintain around a 20mph average with that while the watt meter flipping mostly between 200-300 watts.

Smooth Start. The PAS starts up smoothly. I like it. If I want an immediate boost I can use the throttle. I think the startup characteristics are configurable in the controller programming but whatever settings I have work well right now.

Flat. I did get a flat one day, fortunately it was on the way home and I didn't even notice until later in the evening. The inner tube was some kind of Schwalbe "light" version. I replaced it. The tires seemed a little thin in places -- not really what I'd expect in an "rough and tumble commuting machine". I might have to upgrade those to something a little tougher or get a liner. I usually carry a spare tube w/ me so I'll just see how this goes for a while.

Speedometer. I misunderstood what a 29er wheel means. I finally went out and measured my tire diameter and it's exactly 27.5 inches for my 29x1.6 tire. When I set my dpc-14 display to match the mph and miles were suddenly very accurate.

Gearing. I love the wide gearing I've got. I go from 48x36 to 48x12. I can always find a good cadence even when traveling over 30mph on downhill portions. I could probably do with fewer gears but the shifters I've got make it easy to change 2-3 gears at once so it's no bother at all. I also wind up shifting gears a lot simply because the motor is getting me up to high cadence very quickly from start up. Part of the reason is that I'm being a bit conservative on startups where I’m typically in my 3rd or 4th gear which I've done to decrease load on the motor. Here's my cadence chart (picked 38 tire size b/c 40 wasn't there so it's a little off from true).

Shifting, crunching. I haven't found this to be bad at all. But I'm usually putting in pretty significant effort along with the motor and I can kind of pedal hard for a minute and then ease up to shift. It's a lot like riding a regular bike actually where if your timing isn't right it does shift hard. But it doesn't seem unusual or terribly burdensome unless I'm being dumb about it and shifting under heavy load. I could see how this could be more of an issue if you are contributing very little pedal power -- you can't feel how much power the motor is contributing. I do find that occasionally, while shifting into a higher gear, the motor seems to recognize something changed and it cuts out for a second sort of like I tapped the brake lever but I'm sure I haven't. Not sure if I'm just imagining this or not.

Brakes as clutch. With the shifting being pretty good as described above I don't find myself needing this clutch action too much. But it is there if I need it like if I'm going uphill and have lots of strain on the transmission. It works well when I use it.

Sugru. The Sugru is holding firm. Still looks great. Highly recommended.

Charging. I've only charged at 1 or 2 amps so far but my charger can go up to 5a. I have a small battery so I'm not sure how much faster I should try -- I've read bigger batteries can take more amps and my battery is small. I'll probably try amping it up but monitor heat in the battery while charging. When plugged in, the voltage climbs steadily and then tapers out toward the end of the charge cycle. I've been charging overnight so I haven't been paying much attention to the rate but a couple hours is making a solid recovery on a wiped out battery. Just today I monitored a charge cycle and reported the results below. I can charge to 80% each night and do 2 conservative days of commuting or charge to 100% and do 3 conservative days of commuting at around 20mph with moderate pedaling. My round trip is 10-11 miles. But who am I kidding. I'll probably go 80% each day and blast to work and back, wheeeeeeee. Lastly, make sure you power up the charger first then attach to the battery or you get a spark and snap while connecting. I've read you should connect the powered-up charger to the bike within a couple minutes because the charger has an auto-shutoff and if you wait too long you can get the spark again and, besides, it won't charge.

Charger. The 300w charger works well but I find the fan to be loud and whiny. This is subjective, I know, but let's just say if it's 30 feet away in a quiet garage I can tell you immediately that it's on. The Luna site says they model I have has an upgraded fan to make it quieter but it's still louder than I'd like. One person reported success replacing the fan. With the current fan I would have trouble trying to use it in an office setting -- it would be bothersome. I'm thinking about picking up a fanless charger. If I get that I'll have to solder on a female xt-60 connector on the end because it comes with a 5.5mm barrel plug.

How long does it take to charge? I took some readings on a recent charge.
[pre]Charger @2a, set to 80%.
10:39 -- battery reads 50.3 volts (stabilized overnight)
10:40 -- charger reads 51.3 @plug-in, display reads same or +0.1
10:55 -- charger reads 52.4
11:10 -- charger reads 53.1
11:25 -- charger reads 54.1
11:40 -- charger reads 54.9, tapering off now?
11:55 -- charger reads 55.8, apparently not, fan still on
12:10 -- charger reads 54.7, fan is off, display reads 55.2
12:25 -- charger reads 54.6, fan is off, display reads 55.1
12:40 -- charger reads 54.5, fan is off, display reads 55.1
{Uplug charger}
12:41 -- display reads 55.0
12:55 -- display reads 55.1[/pre]
So that's basically 1.5 hours to put 5 volts on at 2a with the charger set to 80% charge.

What does an 80% charge mean? Some simpleton math would suggest since 58.8v is the max then 58.8*.8=47.04v at 80% charge and 58.8*.9=52.92 at 90% charge. That's clearly not it because on an 80% charge I get to 54.0v-55.0v. Then I thought…maybe it's 80% of the difference between full (58.8v) and cutoff (41v). That difference is 17.8v. Taking 80% of that, 17.8v*.8=14.24v. Add 14.24 to 41 to get 55.24. That's a target of 55.24v for a charge to 80%. And I'm getting around 55.0v so that seems to be a good way to think of it. In practice, I've had variation in the max charge reported by the display when charging to 80%. I've observed between 53.5 and 55.4v with an average around 54.7 maybe. This could be a function of the DPC-14 display not always showing the correct voltage for 52v batteries but I thought voltage levels below 56v were generally accurate.

DPC-14 display. Just noting that the DPC-14 doesn't display accurate voltage for fully charged 52v batteries. More on that here. I might have to give the "user defined" setting a try because Karl reported in his blog post about the DPC-14 display that:
Karl Gesslein said:
In the advanced menu you can set the battery voltage to be User Defined and the display seems to take the voltage that the battery is at initially when you plug it in…

Commute. The bike is great for my 5 mile commute. I definitely can put in less effort and maintain 18-20mph average. It's still cool in Minnesota right now with temperatures ranging from 30 to 45 degrees and I've been able to ride in my work clothes and not overheat. This saves some time changing when I get to work. As summer rolls in I'll need to ride in separate clothes but it's easy to reduce your effort and still maintain speed. I've been talking to some friends at work about it and I can't wait to loan the bike out to them for their own e-commute once the weather gets nicer. Maybe I can convince them to write a little bit about their experience.

Range. I'm still working out how far I think I can travel with the Mighty Mini. I've had varied readings but for now it's looking like battery voltage is reduced by 6-10v for my typical 10-11 mile commute day. That's with pretty strong motor support in the range of 200-500 watts with peaks to 750. That's enough that I can average 20mph even with a few stops at lights. Maybe this is obvious but it seems that dropping volts from 55 to 50 nets you much more work than dropping from 50 to 45 with an even bigger drop from 45 down. That can explain some of the variability in my observations. That, along with different wind conditions and how much I'm asking from the motor.

Range at max assist. My max PAS setting draws 500-750 watts and that puts a hurt on the battery in a hurry. I think maybe I could go 10-15 miles like this from a 100% charge. Another thing that's interesting about riding at max assist is that the voltage on the display is far below voltage at rest (maybe 3-6v lower) and my small experience with this is that you can ride at max assist only until the on-display voltage gets to about the 41v low-voltage cutoff. I don't have exact numbers on this but somewhere around a resting battery voltage of 44-46v is required to allow the requested 500-750watts. Lower than that and the motor starts chugging. From 44v down to 41v you get greatly diminished assist. This will vary with your set up and it's a bit of a rough estimate but I'm thinking of it this way right now:
[pre]Number of watts I can draw based on battery voltage as reported at rest:
58.8v -- 500-750w possible
58.0v -- 500-750w possible
57.0v -- 500-750w possible
56.0v -- 500-750w possible
54.0v -- 500-750w possible
54.0v -- 500-750w possible
53.0v -- 500-750w possible
52.0v -- 500-750w possible
51.0v -- 500-750w possible
50.0v -- 500-750w possible
49.0v -- 500-750w possible
48.0v -- 500-750w possible
47.0v -- 400-600w possible (my PAS 7)
46.0v -- 300-450w possible (my PAS 6)
45.0v -- 180-350w possible (my PAS 5)
44.0v -- 120-250w possible (my PAS 4)
43.0v -- 100-200w possible (my PAS 3)
42.0v -- 50-150w possible (my PAS 2)
41.0v -- 25-70w possible (my PAS 1)[/pre]

Traffic lights. A small benefit I've noticed is that I'm able to boost up to high speeds to avoid stops at traffic lights I wouldn't normally be able to make. I'll blast to the light at max assist to hit the green and then lower the PAS back down. This saves on commute time. The key here for commuting is that I can do this without overheating.

Route. Even with the traffic light benefit described above I'm thinking about adding 1/2 mile to my commute to take a route with fewer lights and potential stops. It's plausible that my commute time could drop along with reduced battery consumption. I might try to measure this and report back.

Fenders. I didn't realize just how well "real" fenders work. Really happy with these.

Chain drop. I've had a few chain drops up until now. Mostly it's been jumping up or down a curb but I had one while shifting down from my largest cog. A chain guide (or reinstall my front derailleur) may be in my future but with most of the drops coming off of curb hopping I also think I may be able to alter my technique to put a little tension on the chain to avoid the drops.

Chain line. It's great. The front chainring is right in the middle of my rear cog. I notice a clickety-clack sound when in gears 1 and 2 but I don't spend much time there.

Suspension-less. I'm completely happy with my decision to forgo the suspension. Like I said in my original post I ride it like a bike and not a motorcycle so using my legs to absorb shock works perfect even at 25+ mph.

Flat bars. Love 'em for the feeling of control in steering and braking. My current riding position, however, is quite upright and, if I had my choice, I'd like this reach to be a little longer. With the speeds I can sustain I can see that an aerodynamic position would be of great benefit. Maybe a stem upgrade is in my future but for now I figured I could use another 6" of reach so I got some long bar ends. In the Amazon reviews someone was nice enough to post pictures with a tape measure so it looks like I'll get at least an extra 5" of reach from them. I think this will help.

Riding tucked. Speaking of riding position, another benefit of the motor is that maintaining speed while riding in a tightly tucked position is much easier. I feel like it takes more effort to maintain the same power when riding tucked and the motor allows me to tuck tightly without having to pedal so hard. You can think of it this way: 1) ride upright, get pounded by the wind, and be in a comfortable position to help pedal to overcome the wind or 2) ride tucked, avoid the wind, pedal with less effort and let the motor do the work -- either way you go the same speed and consume about the same battery. I'm trying to say that the additional effort I would need to exert in #1 is immediately consumed by wind so I think I'll duck under the wind from now on thank you.

Kickstand. The bike tipped over one day and, with the extra weight, I'll tell you it landed with a thud! The handlebar end took a direct hit and easily punctured through the grip. It's not a big deal because I'll need to cut the grips to install the bar ends but this was enough to make me realize a kick stand is a good idea. I ordered a side kickstand.

Street Legal. I was hoping I could easily switch configurations using my dpc-14 display to switch the bike into and back out of street legal mode. I'm now able to do this by simply setting the speed limit on the Advanced settings using the display. I can set the speed limit to 32kph (this is always set in kph) and it restricts both the throttle and PAS to 20 mph. This is just what I wanted but it didn't come delivered this way. I did have to make a change to the controller settings to allow this (see picture below). I'll post more about the controller programming in the future but Luna delivered mine with the throttle tab speed limit set to a fixed 17 km/h. It's hard to imagine why that's the delivered value. I changed that to "By Display's Command" which then opened up the throttle to higher speeds while still being governed by the speed limit that's set on the DPC-14. In the controller settings the speed limit on the Pedal Assist tab came delivered as "By Display's Command" so I left that alone. And again, both the PAS and the throttle react to the speed limit set on the display. Perfect.

Throttle. The throttle was acting like an on/off switch instead of a graduated response. I read up a little and changed settings in the controller and I now have graduated control. See the picture below where the pink handwritten values are what was delivered from Luna and the yellow highlights are my current settings.

PAS vs throttle. PAS is like cruise control. It works well. I seldom use the throttle -- usually only for a quick boost while riding in traffic. I don't think I'd like to use the throttle for long periods of time. In fact I use the throttle so little and adjust PAS so much I switched the controls so the PAS adjust is closer to the grip. Picture below is my left grip.

You can still get good exercise. It's sort of like your PAS level chooses your minimum speed you want to travel and then you can choose to add as much or as little as you want. It's totally up to you and you could completely crank along with the motor if you want.

Torque Sensor. Do I miss not having a torque sensor? I haven't spent a lot of time riding e-bikes with it but I can't say that I feel like I need it. But there is an adjustment necessary -- I probably have to adjust my PAS level a lot more often than with a torque sensor. I don't mind but it's something to consider. For instance if I'm in a parking lot and I'm in PAS level 5 and I pedal 1/4 turn the motor is going to try to get me to 15-20 mph but I probably don't want to go that fast. A torque sensor would know that I'm pedaling lightly and that I'm not asking for much power. The workaround is to set the PAS level down to 1 where I get only a minimum of power. An alternative is to just pull the brake lever slightly to disengage the motor entirely. Or use PAS 0. So if you are a "set it and forget it" person and don't want to be adjusting your PAS levels frequently then a bike with a torque sensor may be right for you. If you think you can handle treating the PAS levels like a cruise control and don't mind adjusting frequently then the BBS02 is awesome.

In summary, the bike is awesome to ride. I just don't even think people understand how small the battery is, how much power you get, how far you can go, and how cheaply you can do it.
Max PAS torture test

Minnesota posted a pretty nice day today and one of the questions I had is…just how fast can I go and how far can my bike take me at that speed? Time for a torture test.

Here are a few details:
  • I did this test out in the country on the side of county highways where I'm not bothering anybody and not passing any bikes.
  • I started from an 80% charge with the battery reading 54.9v.
  • The day was a relatively cool 53 degrees so I felt comfortable pushing the motor hard.
  • My max PAS setting delivers a maximum of 600-750 watts. For those familiar with the controller settings I think the relevant settings to get there are 100/100 for the PAS current and speed limits, Current Limit [A] of 25, and a Keep Current [%] of 60. That's basically 60% of 25a to get 15a. Then take 100% of that from the PAS setting.
  • I got a good mix of crosswind, upwind/downwind, and uphill/downhill but not a ton of elevation change.
  • Total travel weight was 213 pounds. That includes me, a 3 pound u lock, one of my saddlebags with some supplies, a mount for my iPhone, a few small lights. Also included of course is the bike, rack, fenders and I've got the bar ends and the kickstand installed now too.
  • I pedaled moderately hard the entire time. Not enough to get heavily winded and I wasn't standing up and pumping but I was working hard.
  • I did stop briefly a few times to check the heat on the motor.

So how fast can I go? Let's get to the results. I used MapMyRide to track. Don't mind the spanish…I've been learning and I switched my phone to help with that endeavor.

Here's the summary of the ride.

And the splits.

Below I've marked up the velocity vs elevation chart a bit to show what was going on where the elevation change doesn't explain.

Some observations to add to the charts:
  • The "pause, turn around" spot was about 3.8 miles from my starting point. The display was reading 45.5v while riding under load and when I stopped the reading stabilized at 50.3v. So that's 4.6v off the battery to go 3.8 miles.
  • Just after 9 miles I felt the first low voltage chugging from the motor. The meter reading on the display under load was around 41v or 40v. The draw on the watt meter quickly dipped to around 400w and then quickly again to 200w and then quickly below that. This is all in the course of a half mile.
  • A few minutes after I stopped the test the battery stabilized at around 44.0v. As I started out again in a lower PAS level the voltage dipped very fast to 42v and with very low motor support. The 1.8 mile ride home was essentially without motor. I simply couldn't get any wattage out of the battery. I could maybe get a little if I wanted to go 8mph. Occasionally I got 20-80 watts. I think Lithium batteries are known for this -- full power until they cut out and when they cut out, they cut out completely.
  • With the motor-less ride home I can say the bike feels sluggish and heavy without the motor working (but maybe I'm unfair to judge this immediately after the speeds of the test I just ran). The bike functions well but extra effort is required. In my ride home without motor I was able to maintain a 15mph average. I think that would have translated to 18mph on my cyclocross bike.
  • Only one side of the battery was warm. At home I put a thermometer next to the warm side and watched it slowly rise to 98 degrees. This was not exact science, it was probably even warmer.
  • During and after the ride the motor was just slightly warm and the same with the battery. By the time I got home the motor was cool.
  • The battery read 41.8v at home after 10 minutes. After several hours of stabilizing and cooling down to 60 degrees or so, the battery reads 43v. But there is not much left in the tank, I'm sure of that.
  • A torture test on a 100% charge could probably get me about 12 miles in a similar fashion.

Here's the MapMyRide results on the ride back w/o motor support. My effort was about the same as during the test. This serves as a measure of how much effort I was putting in during the test.

And remember, the watts required to maintain speed is not linear. I found bikecalculator.com web site to help me get some numbers and then I graphed them out. From my short ride home without the motor it seems I was putting in about 100 watts myself with the motor making up the bulk of the effort. The graph seems to match pretty well with my ride, namely, that 500-700 extra watts can get you up to around 25-30mph and even faster in the right conditions.

First, here's how I filled out the page (see fields starting with "Units" and down to "Elevation"). Then I changed the watts from 100 to 200, etc. until I reached 800. I scraped the velocity field at each wattage level and made a graph -- that's further below.

Watts required for speed for a 213 lb total load with clinchers (tires w/ tubes) at 1000ft elevation with no grade or headwind.

In summary, the motor is strong and the bike can move fast but the hit on the battery is severe. I knew this was coming but it's nice to have and share some numbers.
Great write up and so much detailI see your Marin is a 2016 model which I guess, is why you got a good discount on it.
My 2017 Muirwoods arrived today and getting it out of the box,it looked tiny compared to my 29er Cannondale MTB.
The wheels are 40mm smaller diameter than the Cannondale due to the different tyres.
I was worried it would be too small for me but once I got it built up it actually feels just right although the handlebar stem was set with the spacers above instead of below!
I am going to try it with them in this position first as it may help with wind resistance.
My plan is to ride it as it is for a few days before putting my BBSHD on it.
I am waiting for SKS Bluemells mudguards to arrive along with a matt black rear rack and have bought a set of blue Cordo Tarpa Plus 38 litre panniers to put my batteries in.

I will run a pair of 6S and 4 of 4S 16Ah Multistars in the left side for 14S 32Ah and in the right side I will have 4 x 6S 16Ah for 12S 32Ah.
The reason for this is because that is what batteries I have!
I've been enjoying this project write up. I have my eye on a similar bike and like the stealthy look of the mighty mini. Good to hear you can get 9 miles out of one. My commute is only 6km return (uphill both ways) so I reckon it would do nicely.
Controller Programming

I'm glad I bought the programming cable. I could see early on that wanted to modify the settings from what was delivered. My priorities were to:
  1. Control the wattage entering the motor to protect it from burnout.
  2. Tweak the power at each PAS level to my liking.
  3. Toggle between street-legal and not by changing configuration in the display.
  4. Offer an entry-level experience with reduced wattage by changing configuration in the display.
Note: I also needed to increase speed of the throttle and smooth out the throttle but I already discussed that in a prior post.

Let's go through these priorities one by one.

1. Control the wattage entering the motor to protect it from burnout.
This one is pretty simple for me based on the performance I'm getting and the watts I'm observing. 750 watts feels like A LOT of power to me and I don't think I need any more to thoroughly enjoy the bike and, besides, my max PAS torture test confirmed that anything more would eat up my mighty mini way too fast for my liking.
[url=https://electricbike-blog.com/2015/08/18/care-and-feeding-for-your-new-bbs02/ said:
Karl Gesslein[/url]"]
Your BBS02 will give you years of service and love if it is treated properly.  The BBS02 loves to eat Watts, but not too many and not too fast. The Pedal Assist system even at its highest setting will only put out around 750 Watts which the BBS02 can eat all day long without overheating
That seals the deal for me. I'll configure my max settings to send in 750 watts.

2. Tweak the power at each PAS level to my liking.
The PAS, as delivered, in level 1, and in my lowest gear, was still propelling me at 13.5mph. As long as I've got 9 levels of PAS available I'd like to try to cut that PAS 1 setting down to something more like 10mph and then gently increase max speed up to 20+mph as I roll through the PAS levels.

Also, knowing that watts required to maintain speed is not linear, I felt that as I moved up into the 400-750 watt range that larger increments between PAS levels were reasonable. You can see what I wound up with below.

3. Toggle between street-legal and not by changing configuration in the display.
I want to talk about the definition of street legal. I often see Minnesota bike laws in summary form, here is an example.
[url=http://www.evelo.com/minnesota-state-electric-bike-laws-definition-bicycle-license/ said:
DEFINITION OF ELECTRIC BIKE: The state of Minnesota (MN) classifies electric bikes as a subset of bicycles. Electric bikes must have a saddle and operational pedals. The electric motor may not exceed 1000W and the motor must disengage when the brake is applied. The maximum speed is 20mph whether assisted by human power or not. If electric bike is operated during night hours it must be equipped with front white and rear red flashing lamps.
The underlined sentence has always confused me because I can pedal a bike faster than 20mph myself. Additionally when you consider the wide range of gearing available on my bike I would have to severely limit rpm to comply with this when in my highest gear -- like somewhere around 60rpm max. So I dug out the actual statute and, thankfully, it's worded more clearly.
MN Statute Chapter 169 Section 169.011 Subd. 27.Electric-assisted bicycle. said:
"Electric-assisted bicycle" means a bicycle with two or three wheels that:
(3) has an electric motor that (i) has a power output of not more than 1,000 watts, (ii) is incapable of propelling the vehicle at a speed of more than 20 miles per hour, (iii) is incapable of further increasing the speed of the device when human power alone is used to propel the vehicle at a speed of more than 20 miles per hour, and (iv) disengages or ceases to function when the vehicle's brakes are applied.
To me, (ii) says that the bike alone can't go more than 20mph and (iii) says that the bike can't assist when you are pedaling it at more than 20mph. I believe I can meet this criteria by configuring these three settings:
  1. Controller -- set the Pedal Assist speed limit as "controlled by display"
  2. Controller -- set the Throttle speed limit as "controlled by display"
  3. DPC-14 display -- set the speed limit to 32 km/h
Prior tests that I've run have shown that with this configuration the motor will cut out at 20mph no matter how hard you are pedaling and no matter whether you are using pedal assist or throttle.

4. Offer an entry-level experience with reduced wattage by changing configuration in the display.
To provide the entry-level experience what I'd like to be able to do is change the number of PAS levels on the display to 3 and have that automatically reduce the max number of watts that can be pumped into the motor by using the pedal assist.

So it's off to the manual for the DPC-14 I go. The last page shows a grid that indicates the 3-level PAS setting in the display uses levels 3, 6, and 9 from the controller. But some quick testing has indicated to me that 6 is not used and it appears that level 5 is the one that's used.

To offer this entry-level configuration, my plan is to "sacrifice" my PAS level 9. Normally this level would be your "all in" 100% setting but I configured mine to a lower wattage, a little above my PAS level 5. Now, when I configure my display to use 3-PAS mode I get levels 3, 5 and 9 from my controller. For what I've got programmed that's 25, 40, and 50 percent of the max 750 watts. That's enough to easily reach 20mph on the flats with mild effort and that's a good entry-level experience.

When I'm riding with 9 PAS levels enabled, I'll typically use PAS levels 1-8.

How to know what to change?
A lot has been written on the controller settings. And a lot of the information contradicts. I think many of us are curious about all the settings in the controller but without more accurate descriptions of the true way they are used we may never know exactly how they all interact. I wonder if someone could reverse engineer the controller programming to ferret out the code? At any rate, because of the number of variables involved it would take a massive controlled testing effort to draw precise conclusions about how all the variables interact. Like many, I think I'm going to fall into a category of setting it up and if it behaves reasonably I'll probably just let it ride. I may publish some testing results just so people know how the bike responds to the programming I use.

Here are a few of the most helpful resources I've found.
  • The bible: https://electricbike-blog.com/2015/06/26/a-hackers-guide-to-programming-the-bbs02/
  • http://www.kiiku.com/29er_Road_warrior/BBS02_C965A/Bafang_BBSXX_Programming_Guide_emax_ebikes.pdf
  • http://www.poweredride.com/info/bbshd-and-bbs02-configuration-programming-resources
  • https://endless-sphere.com/forums/viewtopic.php?f=28&t=58780&start=425
So without further ado, here is how I customized my controller settings.

Basic Tab

Pedal Assist Tab (no changes)

Throttle Handle Tab

I will discuss a few settings that seem to be key to my configuration.

I read the quote below from this forum entry:
Arboh said:
The only problem that I have now is that on PAS I can only get the motor to pull 22.5A.. Exactly 75% of the 30A limit... You can see in my config. file that I have Level 9 set at 100% current and Speed. Looking at your programming you have the "Keep Current" setting at 60%, just like JPLabs stated. Try setting that at 100%.
That's for a BBSHD with a 30A limit but reading it got me thinking. My keep current is set at 60%. 25A is my max setting. Does the math work? I have a 52v battery let's just use 50v. If I take 50v * 25A max * 60% * my Current Limit [%] from my PAS 1-9 settings how many watts would that compute to?
[pre]Let's do the math for my PAS Levels to compute the expected watts:
1. 50*25*.6*.10= 75.0
2. 50*25*.6*.18=135.0
3. 50*25*.6*.25=187.5
4. 50*25*.6*.32=240.0
5. 50*25*.6*.40=300.0
6. 50*25*.6*.60=450.0
7. 50*25*.6*.80=600.0
8. 50*25*.6*100=750.0
9. 50*25*.6*.50=375.0[/pre]
That's pretty darn close to, and in some cases exactly, what I'm observing as my max/peak watts for each PAS level on my dpc-14 display.

I've been riding these settings for about 200 miles now and they are working out very well. I like it. The larger jumps of 150w between PAS levels 5-6-7-8 seem appropriate as that's when I truly need more power as my speeds are increasing at that point and the demands to maintain those speeds also go up.
Chainline Before&After

I had read a lot about people having trouble with chainline and chain drops. Maybe I was mixing BBSHD and BBS02 threads, or maybe most of the issues were with fat bikes, I guess I'm not sure, but the chainline with my BBS02 on my bike with a 68mm bottom bracket is falling right where I'd hoped it would be and I can use all the gears without issue.

I rode the bike about 20 miles before doing the conversion giving the transmission a good workout including lots of crosschaining. I never had a chain drop and shifting worked well. I hoped the new chainring would fall somewhere in between one of the original three chainrings and as close to the center of the rear cog as possible.

Original Bike Chainrings
As purchased…how far was the 48t chainring away from the bottom bracket? Looks like it's about 7/8 of an inch (approx. 22mm).

I found the below diagram searching for "bbs02 schematic". The diagram sure seems to be indicating a 68mm bottom bracket with the BBS02 installed and it's showing a span of 50mm from the center of the BB to the chainring.

So where would that fall as compared to my current 48t chainring that sits 7/8" away from the BB edge? Let's figure it out. The Muirwoods has a 68mm BB so half of that, from the center to the edge, is 34mm. Then from my picture I know it's 7/8" or 22mm more to my current 48t chainring making a total of 56mm away from the center of the BB. The BBS02 diagram shows 50mm. Therefore, if my unit matches this diagram then the new 48t chainring will move 6mm toward the center of the BB from where my current 48t chainring sits. That's near ideal.

Okay, back to present-day where the BBS02 is installed, let's see how it actually looks and measures out. Here's my front chainring with the BBS02 installed. I estimate the distance from the edge of the BB to the chainring at about 3/4". That's 1/8" closer to the center of the BB from the original 48t chainring. From the schematic I had predicted 6mm or 1/4" so it's a little less movement toward the center than I predicted but that's fine as it's a little closer to my higher gears in my cassette where I spend the most time.

And finally let's compare what the chainline looks like at the extremes.

Largest front and back

Middle gear 5

Largest front to smallest in rear

I have had a few chain drops when I hop curbs. And I've had only one when shifting. A simple chain guide I think would prevent most of this. For me, chainline is just not an issue. I wouldn't want a Lekkie Bling Ring because it would just move my chainline more toward the center of the bike which would cause additional crosschaining when in my highest gears right where I apply the most power and torque.

So I guess I'd suggest if you thinking about putting a BBS02 on your bike, take a look at how your chainline looks with your current chainring(s) and then use the BBS02 schematic to find out where the new Bafang chainring will sit in relation to those. If the new chainring will sit somewhere in between your current chainring(s) and you are comfortable with how your current bike shifts to the extremes, then it may be worth saving a few bucks and going with the Bafang chainring.