Bafang BPM wattage limit

[bluesoleli]

Hi Everyone,

Planning to do a build on a cargo bike (Yuba Mundo) and I want to go with a rear drive Bafang BPM motor with the 14mm axle adaptors from Yuba. I really like the Bafang BPM 500W motor as it seems to be getting good reviews and I think 500W is what I need for a cargo bike. The legal limit here is 250W, and being on a Yuba longtail, it's going to attract attention on the road.

So I was wondering if I was able to use a 250W controller to keep it under legal limit and pop in a 500W controller whenever I wanted to go off road? I have also been told to get a Golden Motor universal controller as you can program it on the fly to certain outputs?

Also, on another note, where would be the best place to get one of these BPM motors online? Been looking through Aliexpress but so many choices and getting more lost as I go.

Thanks.

 

[d8veh]

Assuming that you're bound by EN15194, the requirement is a motor with a "continuous rated maximum power" of 250w. Using a diferent controller or current doesnt change the rating of the motor, so it doesn't make it legal. Instead you can use any motor rated at 250w and do anything you like with it to allow higher current, and run it at whatever current you want. There are "250w" BPMs, which seem to be the same as the 350w ones, so try and find one of them. The BPM has a 12mm axle with 10mm flats, so you don't need any adaptors on a normal bike, but I'd advise a torque arm with a 10 × 12mm slot. Don't get one with a 14 ×10mm slot. The motor will twist in it. The "250w" (350w) BPM can go to 22 A. The 500w one can go to 30A, which gives much more torque. You can make a nice label on your PC to stick over the original motor marking which might convince some people. Here's one I made.

 

[friendly1uk]

Which wind and wheel size play too large a role to comment.

I don't think 30 would ever be a problem. I think it was cwah who had the clutch slipping at 35 amps. While other users have used 40 amp.

I think a fast wind in a small wheel would be OK with the 35 amp controller. Because the motor is the weakest and the bike the easiest to move. So the clutch would have the best chance.
If you stick the high torque wind in a big wheel you have the worst case scenario. Quite a lot separates them.

I'm not sure that I like the wiring for much above the 23 amps the 500w controller allows. People are doing it though it seems...

 

[bluesoleli]

Assuming that you're bound by EN15194, the requirement is a motor with a "continuous rated maximum power" of 250w. Using a diferent controller or current doesnt change the rating of the motor, so it doesn't make it legal. Instead you can use any motor rated at 250w and do anything you like with it to allow higher current, and run it at whatever current you want. There are "250w" BPMs, which seem to be the same as the 350w ones, so try and find one of them. The BPM has a 12mm axle with 10mm flats, so you don't need any adaptors on a normal bike, but I'd advise a torque arm with a 10 × 12mm slot. Don't get one with a 14 ×10mm slot. The motor will twist in it. The "250w" (350w) BPM can go to 22 A. The 500w one can go to 30A, which gives much more torque. You can make a nice label on your PC to stick over the original motor marking which might convince some people. Here's one I made.

I managed to track down a 250W Bafang BPM yesterday from aliexpress - scroll down a bit more and it says 350W. Not a problem I suppose, I'll just go with a 500W and do the label method then. I'll play with the controller to put at 25KMH but still get that nice torque curve up to that speed.

 

[d8veh]

Make sure you order one with the right winding speed. It'l have markings something like BPM36V350W 26(??). If you want good torque to a 25 km/h limit, ?? must be 13,14 or 15 at 36v. If you're going to buy one marked 350w, then it might be better to buy it from a known supplier like BMSBattery, Elifebike, Greenbikekit, etc., but ask them to check the markings for ??. Then add a note to your order that that number and the speedvof the motor is important.