Qs205 getting hot after hall sensor replacement

I've been running a qs205 with my sabvoton 72080 flawlessly for quite some time. One day the halls failed on me in a heavy rain situation...and I was already on my spare set. Finally got around to replacing the halls but now I have a new problem. Now my motor gets very hot under any heavy riding, even with regular riding it eventually gets hot. Before I would be able to run my controller full power all day and it get pretty warm at best. Now it gets hot to the point my sabvoton will cut off because of over current protection. Never changed any settings at all. everytime i check the motor when it does this it's very very hot to the touch. It even gets hot under normal riding conditions, and I'm definitely noticing heavier current draw when going slow speeds. I did not change the order of the halls as a sabvoton is very picky and will only work one way anyway. The motor does not feel any different performance wise, it pulls with the same exact torque it did before, except now it just gets hot very fast. Not making any weird noises or anything either like something's holding it back from spinning... any ideas??

The most likely thing is that (even if you don't think it happened) during the replacement, two of the hall signal wires were swapped, in a way that resulted in a false positive, which spins normally, but takes a lot more current, and gets hot.

With a particular controller and motor, there are three good forward combinations, and three good reversed combinations, of hall and phase wires, out of the 36 possible ones.

The rest are split between 12 advanced timing and 12 retarded timing combinations. The ones that come out to be not too far advanced or retarded will still work, but cause higher current and heating. The ones that are too far off simply don't spin at all.

THe only other likely thing is a damaged phase wire that's shorted to the stator at a tiedown point inside the motor, or to the axle somewhere along the way. Or a winding on the stator that is shorted to the stator laminations. Neither of those, by itself, usually causes the problems, but if another thing is also shorted to the bike frame (and thus axle, stator, etc), it might.

test resistance of each phase

amberwolf said:

The most likely thing is that (even if you don't think it happened) during the replacement, two of the hall signal wires were swapped, in a way that resulted in a false positive, which spins normally, but takes a lot more current, and gets hot.

With a particular controller and motor, there are three good forward combinations, and three good reversed combinations, of hall and phase wires, out of the 36 possible ones.

The rest are split between 12 advanced timing and 12 retarded timing combinations. The ones that come out to be not too far advanced or retarded will still work, but cause higher current and heating. The ones that are too far off simply don't spin at all.

THe only other likely thing is a damaged phase wire that's shorted to the stator at a tiedown point inside the motor, or to the axle somewhere along the way. Or a winding on the stator that is shorted to the stator laminations. Neither of those, by itself, usually causes the problems, but if another thing is also shorted to the bike frame (and thus axle, stator, etc), it might.

Click to expand...

Tried every combination in the book or atleast that's what it felt like. Even switched around phases, Eventually got another combo that gave me the same exact problem. Perfectly fine performance but eventually pulling overcurrent after a few minutes of hard riding.. Also I'm pretty sure the sabvoton only works with the 100% correct combination as it is extremely picky with the hall sensors being properly connected to even spin the motor... I'm seriously stumped!

MadRhino said:

test resistance of each phase

Click to expand...

How does one do that?

When the motor gets hot then you should have overheating protection and not over current that can mean two things.


if you were not monitoring your motors temperature at the past not to be more than 140C then maybe the windings have started to fail melt down and the resistance is lower so it's harder for the controller to work and secondly your controllers fets maybe have started to ware out.

Start with measuring your winding resistance to see if they match the initial factory values and if everything is fine then try another controller to test it.

matt912836 said:

MadRhino said:

test resistance of each phase

Click to expand...

How does one do that?

Click to expand...

Set the multimeter to OHM
Test motor big yellow wire with motor big green wire
Test motor big yellow wire with motor big blue wire
Test motor big blue wire with motor big green wire
Test each of them motor phase wires with the motor axle

MadRhino said:

matt912836 said:

MadRhino said:

test resistance of each phase

Click to expand...

How does one do that?

Click to expand...

Set the multimeter to OHM
Test motor big yellow wire with motor big green wire
Test motor big yellow wire with motor big blue wire
Test motor big blue wire with motor big green wire
Test each of them motor phase wires with the motor axle

Click to expand...

No resistance between any wires and the axle. All phases have less than 2ohm resistance between them all.. Number jumps around a little but i think thats due to my cheap multimeter.

icherouveim said:

When the motor gets hot then you should have overheating protection and not over current that can mean two things.


if you were not monitoring your motors temperature at the past not to be more than 140C then maybe the windings have started to fail melt down and the resistance is lower so it's harder for the controller to work and secondly your controllers fets maybe have started to ware out.

Start with measuring your winding resistance to see if they match the initial factory values and if everything is fine then try another controller to test it.

Click to expand...

I dont have a temperature sensor reader on this controller so it's not actually sensing the temperature. It will just eventually power itself off from over current protection, and when I put my hand to the motor it's already pretty warm/almost hot to the touch. Before I could ride at highway speeds non stop and have it just get warm. Motor honestly never got this hot even after hours of high speed riding and wheelies so theres no reason for them to have ever failed.. plus when I opened it up nothing looked out of the blue or smelled funny or anything.

matt912836 said:

No resistance between any wires and the axle. All phases have less than 2ohm resistance between them all..

Click to expand...

"No resistance" means zero ohms, dead short.

Do you mean that, or do you mean "no connection" or "no continuity", between the wires and the axle?

If you mean "no resistance", it means all your phases are shorted to the axle and each other, and could destroy the motor itself or the controller. So I am guessing this is not what you mean.

its a very big mistake for a high power ebike not to have a working motor temp sensor. Maybe the characteristics of the windings have changed because of the high temperatures and you don't know. With the hand you can't really know the inside temperature.

Well , if the phases are about equal impedance (and if they are not shorted with the axle the motor is good. Then, we can assume that you did not damage or shorted any of the phases during the process of hall sensor replacement. Then, new halls are not tested yet, aren’t they?

Motor just caused my sabvoton to fail... wired it up to a regular square wave controller with automatic hall sensor and phase setup so theres no possibility of false positive .. this controller only puts out 30 amps for around 2500w maxx and the motor still heats up to a very hot temperature after a good amount of riding. the sabvoton was sensing the over current as the windings heated up very quick under high power and caused it to draw more current than the controller could handle. this controller wont complain about overcurrent... yet the hub gets hot to the touch with half the regular amount of power... cant be the halls... at this point ready to trash the motor as it just caused me to lose a perfectly good sabvoton..

check this guy from Poland, he can rewind your qsmotor with more cooper for maximum performance.

https://mobile.facebook.com/CyklonEbike/

or you buy a new one with a working temp sensor this time and you won't have the same issues.