ammodave

I've been doing a lot of research here and elsewhere on a possible motor for my first build. What do you think of the BPM 350 https://www.bmsbattery.com/ebike-kits...-bike-kit.html coupled with 36v 10.4ah battery on a 28" Jamis? The BPM seems to have a pretty good rep here and on Endless-sphere. My bike + rider weighs 175lbs. The motor is offered in a 201 and 328 rpm version. Should I stick with the 201 or go for the 328 for use on level ground? A 10mi range is adequate for my purposes.

chvid

I've got a rear BPM 500w running on 48volts, in a 20" wheel on my Catrike road. It is the 328 version. It tops out assist-wise in the low to mid twenty MPH range. I suspect it would fairly similar, maybe 1 or 2 mph lower, at 36 volts. I think you want the 201 version on the bigger 28" wheel. Nice motors - they have a LOT of torque. Not especially quiet though - I call mine the turkey gobbler - you can definitely hear it...louder than a Crystalyte or Bionx or 9C or other direct drive motor. In a lighter road bike, you might consider a smaller motor, like a Q100. Not sure if the 350 watts you referred to is just the same as my 500 watt version (which is based on a 48volt supply). These power ratings are confusing. Also the "301" is supposedly more like 278 rpm. They might have it on the simulator found at the ebikes.ca site. I regularly shock other cyclists with the beastly acceleration of the BPM on the cat. Even a small Q100 will get you into the low twenties, in a 201 version on a 700C wheel, and I like the smaller size too, unless it is really hilly and your combined rider/bike weight is "high" - the quiet is nice. I'm overvolting my Q100s at 48V, but supposedly it doesn't give you much extra power over a 36volt system - the KU63 and 65 controllers are the ones you want - I've had no trouble with the overvolt, but in your case I'd go with a 36volt system - the rest my bikes are on 48volts, so I use that voltage. The KU93 controller is probably a risky choice - too many amps to the Q100 for it to be happy. Whereas I'm running the BPM on a KU123 controller, and I see power spikes to over 1200 watts and the BPM can handle it.

ammodave

Thanks for the info. I don't want a noisy motor and I was trying to avoid the drag of a direct drive. Maybe I need to rethink the Q100. Is it significantly quieter?

chvid

The Q100 is a lot quieter than the BPM, but it is also lighter in weight and less powerful. Both freewheel very well. On your bike, I think you would be happy with either one. The BPM would be better for heavier applications like towing a trailer or very steep hills, or overcoming a disability - the Q100 is good for a roady type feel with light/moderate assist.

ammodave

Will the 250w Q100 (and 36v) give me 20 mph on the flats?

chvid

I think it would - if you mean - "maintain 20mph with light pedalling"...you can see the Cute 100 on ebikes.ca simulator...the 328 version...

On 36V 20Ahr battery, the Cute 100 (328) version...will put you into the low/mid 20s (mph) - with a small amount of assist powerwise into the high 20s which is offset by lower aero at those speeds. The 201 version would hold 20 with no problems and better low end torque for the hills - I'm good for low 20s - maybe 23 with moderate pedalling on the flats since it freewheels so well..But I'm on 48V. Checkout the sim...On a 20Ahr batt you're going to get a ton of range - a smaller battery might be optimal for commuting. Max amps on a 201 is around 15 which is 1C on a 15Ahr pack, well within safety margin for most packs, like a Ping, which is rated as a 2C battery. There is a ton of discussion on Endless-Sphere forum about the Q100 - in particular note commentary of user "motomech" who is very knowledgeable. I think these are nice motors for an "enhanced" roadbike feel and holding speed on hills.

https://www.ebikes.ca/simulator/

ammodave

OK, I'm grasping at straws here. Would there be any speed advantage to using the 24v Q100 and then powering it with a 36v battery. Will 36v change the 201 rpm speed of the 24v Q100? I think what I need is a 250rpm motor but that doesn't seem to exist.