Dead HESC

Amian315

Just Joined
Sep 24, 2020
4
0
Hi all,
I’m after a bit of advice. My wife and I bought ourselves a couple of Carrera E Crossfires with the suntour HESC setup a short while ago. Mine had been fine, hers has died. Unfortunately a trip back to Halfords isn’t really an option as we’re currently in Spain, not returning to the UK until later this year.

So here’s the issue. Basically her bike is completely dead. I’ve tried the following

Her battery on my bike, all good so no battery issue

plugged her back wheel into my bike, all good so motor seems okay

plugged her controller unit into my bike, all good

when you wheel her bike backwards there’s a fair amount of resistance from the motor.
If I plug my back wheel into her bike it still doesn’t power up. If I plug my controller into her bike it’s still dead

At the base of the frame there’s a blanking plate near the crank. I’ve removed it and there appears to be a container with what looks like a capacitor and a number of other components sealed into the container with resin. I’m wondering if something in there has burnt out.

what I’m asking is is it worth trying to source a new one of these parts as I can’t see much else that could be failing

Any advice would be really appreciated as she’s missing her bike and giving me grief.
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
9,822
3,985
Basildon
If you get excessive resistance when you push the wheel backwards, there's a short between the motor phase wires. That can happen after an accident or bad handling damages the motor cable or when a mosfet in the controller blows. These things never happen by themselves, so tell us the circumstances from which the problem started.
 

Amian315

Just Joined
Sep 24, 2020
4
0
If you get excessive resistance when you push the wheel backwards, there's a short between the motor phase wires. That can happen after an accident or bad handling damages the motor cable or when a mosfet in the controller blows. These things never happen by themselves, so tell us the circumstances from which the problem started.
No bad handling. My wife will kill me if I disclose her age but suffice to say she’ll be getting her free bus pass within the next 10 years so she wasn’t pushing it hard and no crashes. The bike has done 37 miles do pretty much new. Maybe something that could have contributed was the outside temperature. It was in the 30’s when we went out for a ride when it packed up 5 miles from home.
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
19,991
8,173
60
West Sx RH
The/a phase connection may have got to hot with the heat esp if the bike was being ridden up any steep gradients or even in to high a gear near to stalling speed.
The bikes system/ controller will need testing but you can carry out a simple free test, disconnect the hub motor cable connector and if the motor resistance goes away then the fault is from the controller to that connector and a phase short.

One can try and get a new controller as some stage via Halfrauds or simply scrap the electronics and fit a KT system for about £80.
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
9,822
3,985
Basildon
That doesn't explain how it happened. Did it start misfiring when you were riding, just go dead in the middle of a ride or what?
 

Amian315

Just Joined
Sep 24, 2020
4
0
That doesn't explain how it happened. Did it start misfiring when you were riding, just go dead in the middle of a ride or what?
After a very long run down a mountain track, probably 800ft decline over 5 miles or so she we stopped for a break. She jumped back on began pedalling on a flat dried out river bed and noticed it was dead and would not power on
 

Amian315

Just Joined
Sep 24, 2020
4
0
The/a phase connection may have got to hot with the heat esp if the bike was being ridden up any steep gradients or even in to high a gear near to stalling speed.
The bikes system/ controller will need testing but you can carry out a simple free test, disconnect the hub motor cable connector and if the motor resistance goes away then the fault is from the controller to that connector and a phase short.

One can try and get a new controller as some stage via Halfrauds or simply scrap the electronics and fit a KT system for about £80.
Could you post a link to the replacement electronics please?
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
9,822
3,985
Basildon
If I take everything you said at face value, my logic says that the motor connector became dislodged in the downhill ride so that there was a partial disconnection. When she started to pedal again, the motor controller gave it's power, but couldn't rotate the motor because of the incomplete connection. That would cause one or more of the mosfets in the controller to pop.

Once popped, it becomes a short-circuit, which will jam the motor when you try to turn it backwards. You can confirm that as the cause by disconnecting the motor connector. If the motor then becomes easier to rotate backwards, you have a popped mosfet and will need a new motor controller, in which case, rather than replace the original, you have the choice to swap to a KT, which will allow a throttle and a speed limit that you can set yourself.