Hub Motor Question

[omar0]

Hello,

I am building multiple emopeds/ebikes for delivery purposes. We first bought a (cheap) batch of readymade emopeds from China. They have each done around 7,000km now after around 3 months. 2 have failed this week due to hub motor related issues. We are guessing it’s overheating. We opened one up and the adhesive for the hall sensors and magnets seems to have worn out.

We are now ordering a larger batch of motorcycles with much higher quality parts. We went for a 3kW QS V1.4 hub motor with a 100A controller from QS as well.

This is costing us double what the first batch of motorcycles did per piece, but we are hoping to get far far more durable mopeds this way.

Any ideas or suggestions on what we can do to ensure the longevity of this new batch? Is our diagnosis of the motors failing due to cheap materials valid, or are hub motors simply not made out for this kind of work yet?

Thanks

 

[lnanek]

A good motor will have a temperature sensor in it. A good controller like the Grin Phaserunner will then read that sensor and thermally throttle limit the bike when needed. Maybe you first generation lacked that capability and just cooked the motors.

 

[amberwolf]

Temperature monitoring and power rollback when overheating would be helpful to prevent undersized / underspec'd parts from damage.

But doing a bit of legwork and math to ensure you buy systems that are designed for more than the worst-case usage you have for them would be the best way to prevent problems.

Note down the worst case terrain (hills, road conditions, etc), worst case winds, highest speed and acceleration required, and for how long all these must be sustained, worst case, and the worst-case total system/rider/cargo weight. Use one or more of the various calculators/simulators like those at ebikes.ca to determine what the power requirements are for this, and then get systems that are *more* capable than that, to allow a margin of safety.

Then get batteries for those systems that are more current-capable (Amps) than the systems will ever need, by at least 20-50%, and that have at least that much more capacity (Ah, Wh) than you need now for the range requirements under the worst case loading. That will mean they will still be capable of doing the required job even after some aging, before you have to replace them. A really good battery is going to cost more than the rest of the system combined, normally.