The known weaknesses of this kind of motor usually occur when too much power is put through them. Their Achilles heel are the thinness of some of the wiring (hall sensor wiring) and the 3 plastic/nylon cogs inside the motor, all the other larger outer cogs are metal. The inner 3 plastic/nylon cogs mean the motor is very quiet when running but if you put lots of demand on them with torque i.e doing a none pedalling start on an incline , then they are known to turn to 'peanut butter' and strip. Whether this also happens due to heat I don't know.
I have 2 running on my bike front and rear 36v. They share a 54v 20Ah lithium pack. I have the magic controllers set to 9amp cont. , 18amp peak. My cycle analyst will show about 800watts peak (typically) shared between the two motors though I have seen 830w. So I presume there is about 400 going to each. I've only had this bike running for a short while and I always pedal when using it, especially important on take off!
My other half has one front 250w motor running off a 54v 10ah pack, same magic controller setting as me, but this pack is probably heating things up though I haven't tested it. The single motor lacks power, it's very tame, no torque. It's more for 'assistance' rather than powering a vehicle, although she loves it.
My two motors can make 23-25mph on the flat without pedalling. Sarah's, probably 17mph and that's with a big pack! , but then again I have not tested hers for any figures etc.
