Winter Project! BBS02 DIY Build

[pre][/pre]
PAS Behavior

I wanted to publish some numbers on how my Pedal Assist settings propel the bike with no effort. I went out a few weeks ago and collected some readings. Here was the set up:

• I used my middle gear, #5, 48x21 gearing, outside tire diameter is 27.5 inches
• Speed limit settings in controller all set to "By Display's Command"
• Speed limit in dpc-14 display set to 99km/h
• Started with full 80% charge at about 54v, went down to about 45v at end of test
• Providing no pedal power, just spin pedal to keep PAS engaged
• Temp: 37 degrees, flat .5 mile circular course, 12mph wind

DPC-14 display set to 9-level PAS



DPC-14 display set to 3-level PAS



Take a grain of salt with the blue Observations area. This was me simply getting a number of quick looks to the display and getting a feel for low/high/peak watts and speed while riding. I was on a closed 0.5 mile course but I did have some corners and curves to manage. As I went faster my observation count decreased because, frankly, it was dangerous. Feel free to peruse the numbers but here are a few conclusions I've made:

Conclusion #1
When I'm in 3-level PAS mode there is no way PAS 2 is mapping to my Controller's #6 as page 11 in the DPC-14 manual indicates. I've programmed a substantial power difference (40% vs 60%) between my PAS 5 and 6. In this test PAS 2 behaved almost exactly like my Controller's #5 setting. I think the dpc-14 manual is not entirely accurate and that a better approximation is that controller levels 3, 5, and 9 are used. It turns out this works really well for me because if you look at my PAS 1-9 settings in the controller programming (prior post) this means in 3-level PAS mode I get an increase in power in each level: 25%, 40%, 50%. That's about 350 watts at most and is enough to get someone up to around 20mph but not much beyond without substantial pedaling.

Conclusion #2
In the 9-level test it looks like I reached max rpm for the motor in PAS level 7 and 8. Note the max speed is nearly identical but the average speed is faster in PAS 8. That makes sense because PAS 8 accelerated me faster and was able to maintain a higher average in corners and against the bit of wind I faced during the test but topped out at the same speed as PAS 7 due to reaching the rpm max. I could prove this out by repeating the test in a higher gear to avoid reaching max rpm. But I don't think I'm that interested to find out. My PAS 8 in a higher gear probably has oomph to get me to a 25mph max rather than the reported 23.

Conclusion #3
Extending observation #2, I deduced the max rpm for the motor is about 120. First I took the cadence chart for my bike (see below) and computed what the cadence must have been to support the listed average and max speed I obtained in the test -- see columns P and Q in the above PAS 1-9 table. From that I deduced a max rpm around 120. Then I computed the expected max rpm I should get in each of my PAS levels by multiplying 120 times the Speed Limit [%] which (I've read) limits motor rpm -- that's column R. If we look at levels 1-4, where I have programmed a Speed Limit [%] less than 100%, the expected rpm computed from the controller's settings matched pretty closely to the actual max rpm's that I computed from road speed (columns Q and R are pretty close). In cases where I never reached the expected max rpm (e.g. PAS levels 5,6, and 9) I probably just didn't have enough current to support the motor spinning at max. I know that's kind of wordy so let's take PAS 4 as an example. The dpc-14 display reported mph max was 18.1mph (col O). With my bike and the gearing I used that mph requires 97rpm (col Q). The controller speed limit for PAS 4 is set to 75% (col E). 75% of 120rpm is 90rpm (col R) which is close.

Partial cadence chart for my bike, I rode in my gear 5 which is 48x21.




Section 11 from the DPC-14 manual

The Weighting Game

I'm just getting around to posting some pictures of how much the components weigh.































This is the total of what I removed from the bike.




Pedals included in above photo because I replaced them.






Axiom Journey rack
http://www.axiomgear.com/products/racks/journey-racks/journey/
1.54 lbs including hardware

Planet Bike Cascadia Fenders
https://www.amazon.com/Planet-Bike-7056-5-Cascadia-Touring/dp/B0041XA1D8
About 1-1.5 lbs


My Ride

• 28 lb bike
• -4.7 Removed components
• +.8 new pedals
• +3.9 rack and fenders
• +9.4 motor
• +.92 cranks
• +.89 chainring
• +.48 display
• +.3 misc
• +3.7 battery
• 28-4.7+.8+3.9+9.4+.92+.9+.48+.3+3.7 = 43.7 lbs

Beautiful bike, clean install and great information about the weight of components added/subtracted.

If you are getting chain drop and you do not want a lekkie because you are content with your chainline, a narrow wide with Samd CNC adapter would be ideal.

Much cheaper option in the long run. The difference with a narrow wide chainring = chain drops become a distant memory.

Lurkin, thanks for the tip. I hadn't heard about the adapters yet. I'll have to look into it. Thanks!

[pre][/pre]
Compare Commute Times and Speed

Two of my main motivations for building my e-bike were to stay cool on my commute into work and to increase the speed. I work in an office and even with just 5 miles I would get warm on the way in. I've got a big fan in my changing room and a small USB fan I can plug into my computer and this combination made the situation manageable last year BE (before e-bike).

High air temperatures are obviously a factor but high humidity is also a major factor. I'll feel hotter on a 60 degree morning with high humidity than a 70 degree morning with low humidity. Sunny vs cloudy matters too. In the heat of summer I simply have to take it easy or I would wind up at work in a near full sweat and would need a shower and take substantial time to cool down; of course that slows me down.

Let's look at some before and after examples. I'm using my commute home here for the main comparison because frankly I just had better data.

So what kind of difference does this e-bike make? Let's dig in.

I've got four before and after examples noted below. The "before" examples are representative of various fast, medium, and slower commutes home on my Masi (cyclocross frame, drop bars, ~23 lb) last year. You can see my speeds and the elevation profile in the graphs below. I usually got stopped at 2-4 intersections either waiting for traffic or at a stop light. I generally pushed pretty hard on the way home and if the temperature was over 40 degrees I came home hot, in a sweat, and needing some time to cool down. I averaged between 15 and 17mph depending on traffic and how hard I worked. Hitting an average mph of 19 was rare, a serious workout akin to sprinting, and took some luck on the lights.

The "after" examples are from commutes home on my e-bike. I'm definitely not working as hard to obtain these speeds.













In all but the first example I can get two full days of commuting (20 miles) out of a 90% charge. That's great because I can cycle the battery every other day and still only charge to 90%. Both of these things help with battery health.

Mostly I ride in my PAS 5 with some bursts up to 6,7,8 to catch some lights or ride in the middle of a lane with traffic. I can ride in PAS 6 for two full days but I'm pretty close to an empty tank after that and I like having the option to rev up one of my four legs of my two day commute cycle if I'm late and need to bust a move.

I'm not tied to the concept of going as fast as possible all the time. I'm completely happy averaging 16-18 mph over the full trip. It's a comfortable ride where I'm putting out effort to move the bike 10-12mph which is very easy for me -- the motor does the rest. It's more about keeping the travel time in a reasonable range and not overheating. I like that I can get two days of commute out of my little battery.

Pedaling along with the assist mode is work even if you are giving only minimal effort. I've had a few warm mornings already and I can report that I still begin to heat up on my way in. I'm not nearly as hot as last year but when the weather is hot and humid you just can't avoid building up some internal heat. I guess I could throttle but I really haven't used it much as it just doesn't feel comfortable for me. Maybe on the hottest days I'll try that a little. As summer rolls on here and it gets hotter in the mornings I'm sure I'll need to consume more juice to stay cool. I'll probably try using higher assist levels in the morning and less after work where I don't care much how hot I get. I feel like I'll still be able to get two days out of a charge but if I get caught on some really hot days where I can't afford to get overheated it's nice to have the option to have the motor do all the work.

I've loaned my bike out to a couple people. We've switched bikes and so I've ridden old-school a bit recently. The difference is noticeable. Without the motor you breath heavier, get hotter, and have more muscle burn and that's all to go slower than what the e-bike can do so easily.

I'm closing in on 1,000 miles and the only issue I've had is that the motor lockring came loose once. I tightened it up about 500 miles ago with some thread locker and it's still tight as can be. I am hearing some kind of short 1/2 second noise occasionally. I can't tell if it's the motor or maybe just rattle or airflow over the fenders. I usually only hear it at high speed but that's also when I'm pumping high watts.

Overall the bike is working spectacularly and it's just a joy to ride.

I'm planning a similar build and this thread is insanely helpful. Thanks so much. Any reason you opted for the 18650 cells you did instead of the others? Did you talk to Luna about how the dimensions and weight of the pack are wrong? I see they're still wrong on the website, which is kind of shitty, unless you just got a weird one-off or something.

"Insanely helpful" I LOVE it. I learned so much from scouring sites where previous builders had shared their experiences. This blog was a way for me to share back and consolidate information for others. It's always great to hear when someone finds it useful.

I picked the battery pack because it was the size I wanted and the particular cells gave me the most Ahp hours (7). Another version of the Mighty Mini can discharge at higher rates but with a decreased capacity of 6Ah. With my BBS02 I'm pulling a maximum of 15amps (750w) so the MM with the Panasonic GA cells work fine in that situation. The Luna site says "For more stable performance in amperages of 30amps such as the BBSHD check out the 30q Mini Cube which has higher amperage cells at a slight lost of range." The MM is so small that it's hard to image when it would be useful drawing 30 amps -- you'd get about 6 miles at 35-40mph, something like that. But some situations might call for that kind of power for short bursts.

I didn't talk to them directly about the dimensions and weight issues on the pack vs. web site. I guess I just felt it was close enough and I threw it into the DIY experience and dealing with Luna who are a little loose on a few things but overall their heart is in the right direction. It's hard to say whether the spec on the web site right now is correct or not "Dimensions: 6 X 2.75 x 3.25 (previous version 6" x 3.5" x 3.125 inches)". If it's really important to you then you'll have to ask them directly before you order because my impression is things can change pretty rapidly and the web site lags behind.

Good luck!

Yeah I was only really considering the 30q, mainly due to Karl saying:

If you have a BBS02 and want to use the throttle then the only 2P pack you should even consider getting is the 30Q. If you are happy using PAS only then the GA or PF packs should be fine. If you have a BBSHD then the only pack that I recommend you consider getting is the 30Q pack, as the GA and PF packs will overheat if you run the BBSHD at the higher power levels or lean on the throttle. Although I really like the GA cells (52v GA Shark pack review is coming soon) they do tend to get pretty hot at high-current draw, at least hot enough so that it makes me pretty nervous.

Click to expand...

I plan to use mine roughly as conservatively as you most of the time, but my commute includes a 500ft climb over about half a mile where I might be leaning pretty hard on the motor, so I figured I'd play it a little safer since I *think* I can still fit everything into the 6Ah (we'll see).

Yeah, I'll ask them about the dimensions / weight. On the category page it says "3 pounds!" and then on the product page it says 3.3 and then your scale says 3.7 .. the .7lb or .4lb difference isn't the end of the world, but rounding 3.7 down to 3 is kind of interesting!

I'm not sure why the throttle would matter vs PAS -- watts into motor can be the same regardless. I read that as an indication that most people run WOT which would be like me running max PAS all the time.

Your climb is significant and much steeper than I encounter on any regular basis. I've been noticing my motor and battery are hotter now that it's summer in MN. If you run in a high heat environment then maybe the 30Q is the pack for you but remember that just because your battery can take it doesn't mean your motor can. I'm finding my motor heats up faster than my battery so with what I know now I'd probably stick with the cells I got and just tone down the speed I go up the hill. In general, it sounds like you are thinking about all the right things. I would guess I'd climb that hill in my gear 2 or 1 which is 46x32 and 46x36 gearing respectively. A half mile is a fairly short distance so I wouldn't worry too much about mine overheating unless I was in 90-100 degree heat. The downside is that I'd have to travel that half mile in the 10-14mph range because of the gearing. But I still wouldn't be breaking a sweat.

FYI I followed up with Luna, they say that they've changed the pack back to its original dimensions of 6 x 2.75 x 3.25 .. I didn't get a clear answer on the weight.

PacoMarkE said:

I would guess I'd climb that hill in my gear 2 or 1 which is 46x32 and 46x36 gearing respectively.

Click to expand...

Ah I thought you had a 48T .. did you switch it out for a 46? Also, this isn't directly related to your build but since I've been wondering and you seem all over this stuff: do you know if the throttle can be configured independently of the PAS mode? Like, can I configure the throttle so it's always giving me the same full power range, even if I'm in the lowest PAS mode (or any other)?

Thanks for the follow up with Luna. I think that pack size will fit better in the bike bag they have.

Oops, I meant 48x on both accounts. You're right I have a 48 tooth chainring.

Throttle is independent of the PAS. I did have to change this from what Luna delivered. I've got a post with my settings. For me, I can be in any PAS level (including zero) and pedaling or not and the throttle will work with variable input from 100 to 700 watts. It works exactly how I'd think.

Pack demensions are pretty easy. The soft packs use plastic seperstots making measurements and weights pretty easy to sort based on numbers of cells. Ive never hadva pack that spoiled a ride when it was lighter or heavier then planned. Size of course is another issue especially with MTB setups.I'll post some triangle pack teardown photos.

Nice thread, thanks for all the weights. Interting stuff, guaranteed to be used by support guys...

Range and Speed

I'm coming up on 3000 miles here and the whole experience has been just awesome. I've got quite a bit of time-on-bike and experimenting behind me and I thought I'd share some more thoughts on the range and speed I’m getting.



When I started looking at e-bikes one of the big questions I had was about range. I found a dizzying array of information and quotes from vendors and in forums that didn't always correlate. Can you really get 60-80 miles out of that bike? If so, at what speed? What started to clear the waters for me was when I found someone that posted different battery consumption rates in terms of Wh/mi. The particular web page is gone now but they talked about range being a factor of five key items: average speed, how much the rider helps, full travel weight, Terrain, and wind. And then they gave estimates that an average rider would use between 12 and 24 watt hours per mile.

I extended that concept of Wh/mi on both ends of the range and doing a little battery math with my Mighty Mini (52v x 7Ah) I came up with this grid for 9 different consumption rates:



So what this is saying is that by "battery math" you can take my battery's capacity and go 40 miles while consuming 9 Wh/mi. For me, two big questions come to mind: is this true and, if so, what does it feel like? What is that like in terms of speed and power? To answer that question I mapped the 8 different Wh/mi battery consumption rates with my riding observations and PAS levels. Some of the details are estimates but many are real life numbers that I've been able to verify with my own rides.



Notes:

1. These are estimates and averages, the numbers can vary as much as 20% based on conditions.
2. I have a total weight (bike, body, bags) around 210 lbs.
3. Assume a 100% battery charge at start.
4. Human effort is listed as "medium". What I mean by that is the effort to ride an average well-maintained bike about 12-14mph. If you want to see what the motor can do on its own with no human input I've got a prior post where I tracked this.
5. Cruising speed is what I can maintain after getting up to speed with medium effort on a level road, with no-wind. Cruising speed is not average speed due mostly to riding interruptions for safety or traffic control. Cruising speed will tend to decrease slightly as battery voltage drops.
6. 3% grade doesn't sound like much but is a decent ascent. I estimated this speed at 3% grade from experience riding a stretch on my commute that's a 100 foot climb over 0.6 miles.
7. My Practical Range is the range estimate I rely on when riding around with me contributing medium effort. It's been trustworthy so far, maybe even a little conservative as I usually arrive home with at least a little juice left even when I’m pressing the limits of the predicted range.

The grid is great but it's a lot of numbers to try to remember. A simple rule of thumb I've been using is what I call the 2520 rule. It states, with moderate pedaling, that I can travel about 25 miles at 20 miles per hour as long as I don't crank up the PAS above 5 for very long. I also have verified rides of 40 miles while using PAS 3-4 so I know I can extend range just by kicking the PAS down and sacrificing speed. I rarely run out of juice but if I do the bike is reasonable to ride without.

That is useful information to know because I still need to get a battery. Now I know what size I need. Your post helped me made the decision on buying the bbs02 and am in the process of installing it to a 2004 Devinci Magma.