Help: Motor Suggestion


1 µW
Feb 19, 2023
Dar es Salaam
Apologies in advance for the long post.
So I might be getting a couple of Electrovaya/Litacore 1kWh cells (7 cells @10.8v, ~72v system, Spec sheet from BatteryHookup attached below), and my plan is to convert a regular commuter bike (Boxer BM150 / TVS HLX 150 for reference) to electric, and I've settled on the QS138 Motor, but I am unsure of what version to go with. Ideally I will be using the bike for daily commute (~15km/day), and later on it might get used for more (~40km/day). I want a good powerful motor but also something that has good acceleration to it for some fun. I do not want much of a high top speed, 90-100km/h is more than enough. I know the batteries are quite large for their application but I have the opportunity to get them for very cheap price, and hence I am planning to build another ebike once I have secured the cells.
I do have experience with converting a petrol scooter to electric, although I had bought a 1.2kw motor (2kw peak) from India when I was studying there and it was what I could afford, using LiFePO4 cells (16s9p, 48v) and it is a good ebike but as you can guess, the speed is limited to 50km/h and I doubt it would have the same power with a passenger on.

So my main question is which of the 138 series would be good and reliable for daily use?, I am not planning to push it for max performance, I will just be sticking with the stock figures, and so far I think the 138 70H v2 would work for my use case, but I am open to suggestions (v3 or 90H or another motor)
- 70H v2 spec sheet says its 6kw continuous/10kw peak, and on another link it says 5.5kw/11kw, what are the actual figures? Is there any "stock" specs for this motor or is it what they have written on alibaba?

- I am also thinking of just getting the 138 90H, seems to be v3 only? and which has a peak of 13.3kw and messing with it to at least get full amps out of my cells ( say 200-220A @72v so I could push to 15-16kW just for the heck of it, I mean at least I can try it and see what it feels like then tone it down) as the price difference between the two seems to be about 150USD

- What is the actual RPM of these motors? As I see some come with the integrated reduction gearbox, They say its 3000RPM so I assume it is the RPM at output shaft correct? or do all the 138s come with reduction? I will be directly driving the rear wheel off the motor giving 1:3 reduction (45t rear sprocket) on a 21inch tire so I need to know output shaft RPMs for top speed calculation correct? Flux weakening means overdriving the motor right? like I am planning to use the motor "stock" so I should not consider the 6000RPM with flux weakening right?

- what would be comparable to a 150cc commuter bike like the ones I've mentioned?
TVS says their max power is 8.9kW@7500 and 12.3Nm@5000
I've also ridden a Suzuki Gixxer 150, which is 10.9kW@8000 and 14Nm@6000
Is the 138 70H gonna feel like either of these two? or much better or worse? what about 90H v2/v3?
I know you can't compare apples to apples as engines develop their power and torque gradually across the RPM while motors are much much quicker if not instantaneous, even my 2kw feels zippy when you get going compared to the 125cc that was in it before.

-Which controller would you suggest? the sales rep on Alibaba suggested this fairdriver kit to me, while I've mostly been seeing the EM150 controllers, what is the difference apart from their rated powers? Ease of use? Reliability? I assume you can program all of them from what I have read, and adjust the throttle curves and such, I would like to have that functionality. The rep also told me that the 70H v1 and v2 are the same motors in terms of performance and internals, jus that they have different outer casings (for different type of mounting)

-I will need to get a BMS, I know Daly is one of good ones you can get and the 2 battery packs I use batteries have them (48v 40A, 60v 60A), although I have the 'dumb' BMS and not those with Bluetooth and other smart functions, would those be better or not? or another brand of BMS? what about BMS with CANBUS? does it do anything else (apart from showing amps on the speedometers and such?

Any other advice/suggestions would be appreciated, I've been lurking this forum for a long time and just made an account yesterday to get some proper insight now regarding my second project.
I have an Instagram page here if you're interested in seeing my progress on my scooter (It's up and running right now, Just need to make a proper battery box, repaint the bike and finalize the rear swing arm design)
Once again sorry for such a long post, I just want to make sure I am going with the right components this time because it is financially more (~1600USD) than my scooter project whose motor I got for cheap and batteries for free.(~250USD)


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I know Daly is one of good ones you can get and the 2 battery packs I use batteries have them (48v 40A, 60v 60A), although I have the 'dumb' BMS and not those with Bluetooth and other smart functions, would those be better or not? or another brand of BMS?
Daly's track record is Not as Good as Daly's market share would indicate. Yes get a smart bms with bluetooth there are many brands Ant, JBD are two I can remember atm.
Later floyd
many questions here.. to many to answer in one post but i’d stay away from the Votols at this time, their program is too screwed up and go with a fardriver, (i’m not sure how fardrivers correspond to their ratings so i’d go one size up from the kit linked.)
I’d choose LLT Bms instead of Daly which has a shaky reputation.

The 138 70h with a gearing for about 100kph can get you wheel flipping acceleration if you have the right controller and battery, i think i’d still choose the 90h if i was building with a heavier bike as a donor as you seem to want to do. The geared qs mid motors are nice to avoid a huge rear sprocket but they get wide - check chainline and motor position works for you before getting this one.