History - Wisper 705 Torque with 575 battery. It's approaching 7 years old and recently started losing assistance after about 20 miles. Stopping would see assistance returning sometimes, or it could might come and go when pedalling. My suspicion was the battery was failing because of its age and people I sought advice from didn't disagree. I chose not to have the battery tested and save the money for replacing it.

 

Had the battery re-celled as the "cheapest" option. First ride today, and the problem manifested itself almost immediately

Assistance came and went much like it was doing after I last rode over 20 miles.

 

I checked all connections (again!) and took the controller apart having read that failure of it can cause symptoms like mine.

 

Inside there is an overheated component and a burnt spot on the case adjacent to where the component is.

 

My questions are;

 

1 - What would cause this, and would changing the battery have any influence on the cause?

2 - Should I be looking at anything else - motor, torque crank?

3 - Is the controller repairable, or will other components on the circuit board have failed? ( Replacement is out of stock at Wisper?)

It's the resistor that cuts down the voltage for the 12v regulator. It's probably still OK - just been running hot. It's quite common to see them like that. It's probably an indication of a problem elsewhere. It looks like that burn on the inside of the box might be from a short. Can you see anything that might have touched it?

No, can't see anything obvious that would have touched it other than the wire coming out of the top of the resistor.

No, can't see anything obvious that would have touched it other than the wire coming out of the top of the resistor.

The resistor looks well- cooked. It's consequential damage, so there must have been a short somewhere. Maybe a MOSFET is blown or there was a short on the 5v somewhere. It's probably best to get a new controller, but when you get it, connect only the battery and control panel, then check the 5v after you connect each other connector. If there's a short on any of them, the 5v will go right down.

Thank you. How do I make this check and what reading am I looking for?

 

I understand the connection part (I'll work out which connector goes to the panel using this controller) and I have a multimeter.

 

If I have to probe the connectors which ones and which probe wire?

 

If I need to test the thick yellow, blue and green wires into the big julet plug there are 3 longer pins (of 9) - is it those?

Edited April 18, 20242 yr by Forty45

The resistor looks well- cooked. It's consequential damage, so there must have been a short somewhere. Maybe a MOSFET is blown or there was a short on the 5v somewhere. It's probably best to get a new controller, but when you get it, connect only the battery and control panel, then check the 5v after you connect each other connector. If there's a short on any of them, the 5v will go right down.

 

Saw your reply to my post on another thread. My response is below;

 

I'm happy to improve with a different controller and LCD. Can you point me in the direction of where to buy and what to go for please?

 

Am I going to have to replace the connectors too?

 

My main priority, as you say above, is to identify the cause of the problem and not fry anything else. Is that possible to do with the old controller?

Saw your reply to my post on another thread. My response is below;

 

I'm happy to improve with a different controller and LCD. Can you point me in the direction of where to buy and what to go for please?

 

Am I going to have to replace the connectors too?

 

My main priority, as you say above, is to identify the cause of the problem and not fry anything else. Is that possible to do with the old controller?

Inevitably, when you replace a controller, you have to do something with the wires and connectors. If connectors don't match, I always cut them off and join the wires directly. You don't need connectors. The wires are in principle the same on every controller.

 

We always recommend KT controllers with any of their LCDs except LCD1. LCD4 looks cool but is a bit difficult to operate with gloved hands.

 

You can't get them from Ebay, Aliexpress, Amazon, Topbikekit, BMSBattery and other Chinese resellers. If your bike doesn't have a throttle, you should get one too because you can set it up legally with these controllers also, if your bike doesn't presently have an LCd, you should get a speed sensor.

I've asked The Layer Laboratory (Torque Tech) and Ebike Solution to suggest a controller.

David has also responded and offered help repairing (if possible) mine and cautioned that an aftermarket one wouldn't be optimized to the bike etc. in the way his is.

As there are probably 28 wires from the controller I'm not sure individual connectors for that number would work well as the controller is housed in a small space behind the battery and it's very cosy putting the top on it as it is with the Julet connectors.

My bike had an LCD - a Wisper version of what you may know as a W108 (or possibly a Bafang C961).

Could you explain how to do this please "when you get it, connect only the battery and control panel, then check the 5v after you connect each other connector. If there's a short on any of them, the 5v will go right down"?

I've asked The Layer Laboratory (Torque Tech) and Ebike Solution to suggest a controller.

David has also responded and offered help repairing (if possible) mine and cautioned that an aftermarket one wouldn't be optimized to the bike etc. in the way his is.

As there are probably 28 wires from the controller I'm not sure individual connectors for that number would work well as the controller is housed in a small space behind the battery and it's very cosy putting the top on it as it is with the Julet connectors.

My bike had an LCD - a Wisper version of what you may know as a W108 (or possibly a Bafang C961).

Could you explain how to do this please "when you get it, connect only the battery and control panel, then check the 5v after you connect each other connector. If there's a short on any of them, the 5v will go right down"?

Your present controller isn't optimised for your riding. Most after-market controllers have settings to make them work with the motor and other stuff and you can optimise them to your needs. As I said, all controllers work the same with the same wires for the same things, but if you get confused by 28 wires, you probably shouldn't be messing with these things.

Best optimised controller I have used is a KT.

I've taken up David on his offer to return it to Wisper for repair and testing. If that works I'll be happy.

Only EBike Solution have come back to me, suggesting a Bafang controller which they advised may not work with the torque sensor, which would not be any use to me if it didn't.

New resistor fitted and controller tested. Worked with no problem for a 20 odd mile ride, so I'm happy with that.