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Electrifying a cargo bike - Mid drive or Hub?

Klang426

10 µW
Joined
Oct 5, 2023
Messages
5
Location
Chicago
Hi everyone, first post here, I've been reading the forum for a while but have some questions to ask so I'm hoping some of you e-bike wizards can help!

I'm getting a Madsen cargo bike and I want to electrify it. Here are the details:
  • Total weight (me plus 3 little kids), about 300 pounds. That will obviously increase a little with time.
  • Cruising speed 12-20 mph. No real need to go above 20.
  • Desired range, up to 20 miles with pedaling would be great.
  • Riding on paved roads, generally flat but with a few short, moderate hills. Occasional offroading but always flat in that case (think rail trail).
  • Budget - $1500ish.
  • Madsen bike has a 20" rear wheel and 26" front wheel.
My priorities for this are safety and reliability. I want high quality stuff because I'll be carrying my kids and I also want it to last a long time. I don't want constant maintenance. I also want a safe, high quality battery. (I don't want to buy an off the shelf ebike because everything tends to be proprietary.)

I am trying to decide between a BBS02 and the Grin All Axle (the Madsen bike has thru-hole axles). Madsen recommends the BBS02 but they sell the kit for $1815 which seems really steep. The Grin all-axle seems like a good option because it strikes me as high quality and reliable and the regen concept is cool. I guess I'm leaning towards the all-axle and buying the full-up kit, batteries and all, from Grin.

But which motor is the better option for my use case? Or is there some other motor/kit that you recommend instead?
If I want a safe/reliable battery, Grin or Em3ev seem like good options - any others?

Any help/recommendations are appreciated!!
 
The quote below is from Grin tech support, in response to my question about choosing between the GMAC 8T & 10T. I don't know much about this, but posting it here may provoke comments from others who do:

me: Apart from top speed, is there some other real situation where the 8T is preferable over the 10T?

Grin: The application of the motor can also be a determining factor. For example, if you are using the motor for off-road or heavy-duty purposes, then the 10T motor may be more suitable as it can handle a higher load. On the other hand, if you are using the motor for commuting or urban riding, then an 8T motor may be more suitable due to its better efficiency.

This isn't the All-Axle, it's the GMAC, but I think the concept would apply. The All-Axle is the only hub motor I know of for use with thru-axles (I did this on my Cruzbike), and it also comes in different winds for different top speeds. Given your speed choices, I would choose the slow 8 turn stator, or standard 6 turn stator for this reason.

Simulating the All-Axle in those winds suggests the standard 6 turn for your scenario:
All-Axle 8T & 6T
 
Great post Klang.

The only info you might’ve added is how mechanically adept you are, and the frequency and type of service schedule that you’re willing to engage in. This is relevant to the mid-drive vs hub motor decision.
 
I'm sure there is quite a bit included in the $1815 BBS02 package but remember that a BBS02 with display is around $350 these days.
 
My BBS02 has been perfect for eight years of off road MTB without any maintenance. Unless you have some overriding reason to purchase the hub, I'd say the mid is the better option. em3ev is an excellent choice choice for batteries although I've had good service from a domestic supplier.
 
I see several dozen cargo ebikes a day, during their morning and afternoon commutes. Most have two kids, the smaller step through cargo ebikes carry one. The trail/path is flat, but the area is hilly, so eventually they need to climb steep hills to get home. I'd guess about 5% have hub motors, the rest are mid drives. Of the mid drives, maybe 5% are DIY, and those are mostly BBS02's but sometimes a BBSHD. Just based on those observations, I'd say the BBS02 seems fine for a DIY cargo bike with a few moderate hills, although with all of that room and weight not being a big factor, I'd personally go with the HD.
 
Neat bike, first rear bucket cargo bike I've seen, mostly see front.

How do you feel about pedal assist modes? The bbs02 only has a cadence sensor whereas the all axle could be used with a torque sensor in the bottom bracket hypothetically. There are also other mid drives such as the CYC photon that have torque sensors. If you plan on riding throttle only that's a moot point though.

Having ridden both direct drive and a mid drive (I currently use a photon that I mentioned above) I find the direct drive experience more pleasant but the mid can climb anything. On throttle with the mid I find the chain tends to slam a bit when throttling on and off and gear changes are clunky cause you have to cut power. When exclusively pedaling it's pretty smooth but sometimes I'm tired or my knee hurts :p The direct drive is just twist and go, always smooth as butter. Plus regen is neat. Not crazy significant returns but is nice for saving brake pad wear.

That big long chain also gives me pause with the middrive as it does run through the chain. I'll let the longtails and recumbent trike owners with mid drives speak to how much that matters though.

Summary: Unless you've got lots of hills I suggest the direct drive. Of course this is just one opinion and your mileage may vary.
 
I would suggest a hub drive from Grim due to the drive train layout with long chain. You didn't mention whether you are considering front or rear hub. The specs for this manufacturer show the frame as chrome moly but there is no mention of the fork. If you go with a rear hub you may need an extension cable.
 
I am trying to decide between a BBS02 and the Grin All Axle (the Madsen bike has thru-hole axles).
It's sad that they caved to pointless fashion, but that's how it goes sometimes. The rule is profit or die, and it clearly helps if you can appeal to mouth breathers.

I think you should work the benefits of that 20 inch rear wheel by putting a hub motor there. Doing that will decrease your bike's maintenance requirement overall, because it's reducing the load on the chain drive components.

Using a Bafang mid drive multiplies the amount of maintenance you'll have to do, by a lot. It could be worth it if you have brutal hills to contend with. But it sounds like that isn't your situation.
 
I have a Juiced ODK with front geared hub which works really well. it’s great to have 2 independent drivetrains; if your chain snaps with a mid drive you are stranded! A bit of reassurance with the little one on board that it is very likely to get to the destination. If those front forks are steel you could consider a high geared front hub. The larger wheel wouldn’t make it accelerate fast but it would still work ok.

There looks like only one option for thru axle rear hub which is direct drive hub. That would give you regenerative braking and be pretty zippy in a small wheel.
 
Great post Klang.

The only info you might’ve added is how mechanically adept you are, and the frequency and type of service schedule that you’re willing to engage in. This is relevant to the mid-drive vs hub motor decision.
I'm familiar with basic bike maintenance but electronics less so. I'll do whatever maintenance is necessary to maintain the system, but the less maintenance the better. From the feedback so far it seems like the hub motor / All-axle is the winner. The proliferation of mid-drive systems on cargo bikes is odd though and does give me pause. I guess mid-drives are better if hills are involved so maybe one could argue a mid-drive is better overall if you're willing to put up with extra maintenance.

I'm open to a front or rear hub motor, as far as I know the front fork of the Madsen is steel (would someone put an aluminum fork on an otherwise steel frame?), but since the rear is stronger and has more weight over it I'd prefer to go with that. I am a little concerned that the rear all-axle motor may not fit due to space constraints with the bucket mounted on the back of the bike.

Another question...Is a 36v battery sufficient for what I want or do I need 48v?
 
rear all-axle motor may not fit due to space constraints with the bucket mounted on the back of the bike.
I looked up the bikes. There are rear-quarter views showing a sprocket cluster on the right, and a disk brake rotor on the left. You will have no problems as the motor fits in between these and the width is standardized (enough) to be certain of.

You aren't choosing the electric models of that bike - because you aren't buying from them, or do you have a reason that might fit into this discussion?
 
Good to know the rear all-axle should fit!

Yep I plan on buying a used one. You can find a used but still like-new model for $1500 less than a new one.

Did some research on kit prices and an all axle kit from Grin (motor, battery, everything) is around $1750. Meanwhile EM3ev has a BBS02 kit for about $900. Tough decision…
 
For what its worth, the Madsen comes with a BBS02 from the retailer...

Speaking as the owner of a BBSHD equipped cargo bike, the hub motor is likely simpler and more reliable if hills nor extreme loads are a factor. I have gone through so many chains.
 
Since the rear wheel is 20" size, it would be ideal for hub motor, since smaller diameter wheel would allow higher torque (to climb hills),
far less complicated (& cost) conversion than mid-drive conversion.
 
I have gone through so many chains.
That's interesting. I'd love to ask about your programming and riding style.

As the owner of a BBSHD cargo bike that routinely carts my large self, my wife, and all kind of other stuff on it around our town, I programmed mine quite specifically and haven't had any chain problems at all 😁

As others have mentioned, hub are simpler but have their own tradeoffs. I'd still go mid if I was going to do it again. Both for the obvious tradeoffs and because the BBSHD being fully programmable makes it more flexible and helpful than most other setups out there. Tuning things to work best for you is the best feature of all.
yuba.jpg
 
  • Total weight (me plus 3 little kids), about 300 pounds. That will obviously increase a little with time.
  • Cruising speed 12-20 mph. No real need to go above 20.
  • Desired range, up to 20 miles with pedaling would be great.
  • Riding on paved roads, generally flat but with a few short, moderate hills. Occasional offroading but always flat in that case (think rail trail).
  • Budget - $1500ish.
  • Madsen bike has a 20" rear wheel and 26" front wheel.

FWIW my total rig weight when it's just me commuting to work is likely ~350lbs. Cruising speed is also 12-20, though I sometimes get closer to 23-24 when I have to ride in the road / cars. I got a very large capacity battery so my range may be between 70-100 miles, though I've never tested it straight-through.

JNO can get you the BBSHD motor parts for $700 and a battery has many battery options, almost all of which would very likely cover a 20 mile range.
 
That's interesting. I'd love to ask about your programming and riding style.

As the owner of a BBSHD cargo bike that routinely carts my large self, my wife, and all kind of other stuff on it around our town, I programmed mine quite specifically and haven't had any chain problems at all 😁

As others have mentioned, hub are simpler but have their own tradeoffs. I'd still go mid if I was going to do it again. Both for the obvious tradeoffs and because the BBSHD being fully programmable makes it more flexible and helpful than most other setups out there. Tuning things to work best for you is the best feature of all.

That is one good-looking bike! By programming do you mean indexing the gears properly to ensure the shifting works with the front chainring being different? And even if that's done properly, doesn't the extra force on the chain mean you have to replace it more often?

What voltage is your battery? Do you find it to be more power than you need or about right?
 
You can plug your laptop into a BBSHD/02 and change dozens of different settings. Read up here if you want to know more.
Yeah, this is what I meant — plugging in to the motor's controller firmware and configuring various parameters to meet your specific desires. A motor tailored very specifically to your needs rather than the general public's.

You do still want to figure out the right gear ratios for your given load, torque, and top speed needs, but the way the motor itself ramps in power and works with you to deliver that power efficiently is totally changeable.

I wrote up my own 'programming' here. It focuses on tuning the pedal assist functionality to pedal WITH you, not run away with you (cadence-wise) so that you're ghost pedaling. I hate ghost pedaling 🙂

 
I wrote up my own 'programming' here. It focuses on tuning the pedal assist functionality to pedal WITH you, not run away with you (cadence-wise) so that you're ghost pedaling. I hate ghost pedaling 🙂

When I lived with BBS02, I did that with gear selection and crank length. In my case that meant using 152mm cranks when I usually use 185mm or longer.
 
When I lived with BBS02, I did that with gear selection and crank length. In my case that meant using 152mm cranks when I usually use 185mm or longer.
Yeah you can get away with that with the BBS02 since it's lower-power than the BBSHD, but that still essentially means you've just found the crank / gear ratio that you can still pedal with while the motor is at max power... meaning the motor is running at max power all the time. I strongly prefer using actual config values to get the motor working in my favor while saving battery juice and keeping great motor longevity 😁
 
I strongly prefer using actual config values to get the motor working in my favor while saving battery juice and keeping great motor longevity 😁
If you want your pedaling to contribute in order to save battery juice; it's more like motor assist. You can also do either by disabling PAS and using the throttle to manage the assistance level.
 
Yeah you can get away with that with the BBS02 since it's lower-power than the BBSHD, but that still essentially means you've just found the crank / gear ratio that you can still pedal with while the motor is at max power... meaning the motor is running at max power all the time.

Actually I was shooting for 80% of free speed, on the presumption that was closest to max efficiency.

Free cadence of BBS02 is slower than HD, and my practical cadence on shorty cranks is pretty fast.
 
You can also do either by disabling PAS and using the throttle to manage the assistance level.
Totally true, just way more manual management than I want. My motor just helps me get to ~85 rpm cadence and helps me stay there if it slows down (either due to up-shifting or starting to go up a hill)

Actually I was shooting for 80% of free speed, on the presumption that was closest to max efficiency.

Free cadence of BBS02 is slower than HD, and my practical cadence on shorty cranks is pretty fast.
Totally fair — yeah I wish there was a version of the BBS motors that had the power (actual motor) of the HD but had a larger down-ratio that brought max efficiency at right about 90-95 rpm. That'd be a real dream for pedelecs. This nonsense of 150-160 crank rpm on the BBSHD is just useless for those of us that want to stay mechanically connected to the drivetrain.

At least power is still extremely there at 50% of that! 🙌🏻 BBSHD FTW.
 
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