BPM2 or Q128 conversion kit? (Copied from my post to Reddit)

One last question for everyone here. Planning on pulling the trigger on my conversion kit order from BMS Battery and cannot decide between the two. This is for a front-wheel application. I see Q128 comes with a 9 mosfet 450W controller and the BPM2 a 12 mosfet controller. Also the Q128 is listed 4-500W vs 500W BPM2. Other than that and the fact the BMP2 does not specifically state rim brake compatible there seems little to justify the $50 difference between the two. Any experiences and comments regarding the two?

Given the shipping cost I would like to get things right the first time! Thank you.

I'm not sure what controller you reference. Perhaps you could specify the models you are considering, and whether you want to use throttle/PAS or both. I say this because I have the S12S "500W" controller and it pushes 1000W on max setting under throttle. Its minimum setting is just over 500W without option to reduce any further. This is under throttle response, and the PAS settings should allow greater reduction in wattage.

Unfortunately that is about all that BMS lists on their website for information. I am inferring from the information they list that for the Q128 they are using their S-KU95 and for the BPM2 the S-KU125. I plan on using both the PAS and throttle.

S-KU95 (https://bmsbattery.com/ebike-kit/801-s-ku65-for-led810-250w15a-6mosfets-controller-ebike-kit.html)
S-KU125 (https://bmsbattery.com/controller/806-s-ku65-for-led810-250w15a-6mosfets-controller-ebike-kit.html)
BPM2 kit (https://bmsbattery.com/ebike-kit/346-bafang-bpm2-48v500w-front-driving-bike-conversion-kit-ebike-kit.html)
Q128 kit (https://bmsbattery.com/ebike-kit/346-bafang-bpm2-48v500w-front-driving-bike-conversion-kit-ebike-kit.html)

Can't make a side by side comparison for you. Last year I bought the Q128h 201 rpm motor and a S12S 500W Torque Simulation Sine Wave Controller. The two work together seamlessly and I am very happy with the combo. Very smooth, very quiet, and an amazing amount of torque to get up the hills.
I had an unfortunate occurance this winter when my cover leaked litterly filling the controller with water plus I had left the battery plugged in. The battery was flat dead and the controller a soggy burnt up mess. I built a new battery pack and ordered another S12s controller and I'm back to enjoying the Q128.

molybdenum said:

I'm not sure what controller you reference. Perhaps you could specify the models you are considering, and whether you want to use throttle/PAS or both. I say this because I have the S12S "500W" controller and it pushes 1000W on max setting under throttle. Its minimum setting is just over 500W without option to reduce any further. This is under throttle response, and the PAS settings should allow greater reduction in wattage.

Click to expand...

But there is an option: cut one of the two shunts.

motomech said:

molybdenum said:

I'm not sure what controller you reference. Perhaps you could specify the models you are considering, and whether you want to use throttle/PAS or both. I say this because I have the S12S "500W" controller and it pushes 1000W on max setting under throttle. Its minimum setting is just over 500W without option to reduce any further. This is under throttle response, and the PAS settings should allow greater reduction in wattage.

Click to expand...

But there is an option: cut one of the two shunts.

Click to expand...

Very true, cut one shunt and halve the amps. You can even file away some of the shunt(s) to get a more refined reduction...

As for the S-KU95, little is known about it except that it works with the LED810 Meter Panel and it is new to BMSB. As a sinewave controller, the S12S runs the motor whisper quiet and it can be programmed through the SLCD3/SLCD5 interface. I couldn't find anything on BMSB or otherwise regarding programming parameters for the S-KU95. Maybe someone here knows something about it? Certainly, an option is to buy the motor, S12S and SLCD3 display separately from BMSB I'll bet these aren't much more expensive than the Q128 kit.

I filed a shunt once and didn't get all the metal particles cleaned out and as soon as I powered it up, it zapped the ICB

Thank you all, but we may be digressing a bit. As controllers are easily replaced why not concentrate on the motor itself? Is the BPM2 worth the extra cost?

I think BMSbattery feels the BPM2 can handle more power as they bundle the kit with a 30A controller, whereas the Q128 comes with a 22A controller. Neither controller supports an LCD, just the 810 LED display which means you have 3 PAS levels. My first ebike kit came with an 810, and the pedal assist is a bit abrupt at low bike speeds. I'm used to it, but it scares newbies, especially if they haven't ridden a bike in years. The torque simulation controllers feel better, in part because the first assist level is pretty mild.

Bafang ships close to a million motors annually. I think it's a "big name" in ebikes because of what they also do in the mid drive market. If this was a one time buy for me. i'd be willing to pay a little more for the bigger controller, possible higher power, and "name" and get the BPM2. However, I've put together a few kits, and now I look at lower cost. I'm pretty sure a Q128H would work. I bought a bare Q128H last December ($140 shipped). Not installed yet.

For someone in the USA, the ebikeling 500W front motor kit for $209 shipped on ebay looks pretty good to me. Comes with SW900 LCD and a 22A controller. Might not be available in 700cc, but 26" is available. I bought one of those too. While also not installed, I have tested it. It runs on 48V. My first ebike kit in 2015 came from him. Same motor. Has worked fine.

docw009 said:

For someone in the USA, the ebikeling 500W front motor kit for $209 shipped on ebay looks pretty good to me. Comes with SW900 LCD and a 22A controller. Might not be available in 700cc, but 26" is available. I bought one of those too. While also not installed, I have tested it. It runs on 48V. My first ebike kit in 2015 came from him. Same motor. Has worked fine.

Click to expand...

I considered this. They are also selling them on Amazon. However I have not been able to get a response from them about if this is only 36V as listed, or can also run at 48V. At the moment I have (4) 6S 10Ah 22.2V lipo from the recent HK sale. I probably should have went for the 3 or 4S combos but the cost-per-Wh for the 6S was very compelling.

Thank you.

One thing to keep in mind is that the BPM is bigger and heavier than the Q128. I haven't tried either although I have a partly completed bike with a rear BPM, but I'd be cautious about putting that much power and weight on a front wheel.