I modded internal mp 3 controller - worked great until...

[Sanfrancisco]

Dear all,
Frustrated not being able to get more than 25A from the internal controller, I opened it up and doubled all copper wires on the back of the controller board. I also added a bit more solder. When I put everything together (about 4 hours of work) I went on a bike ride and had a smile on my face. I saw a peek 38A at 53V.
No San Francisco hill would be too difficult for the MP3.

Very happy went to climb twin peaks. The motor cut once but restarting it moved back everything to normal.

On the way down at some point I hit breaks (had 100% regenerative breaking) at maybe 25 miles/h and my joy ended. Most likely one of the fets shorted. A strange sound started coming out of the motor. The very machanics of the motor are ok - checked it by cutting all phase cables and the motor moves smoothly.

What could have happened?

At any rate frustrated that the controller broke down not by going up by going down, I called Lyen and got an external controller which I am now installing.
 

 

[GoldenMotor]

This is challenging issue for all EV controllers. The reason is that when the vehicle is downhill at fast speed exceeding rated motor speed, the motor becomes generator, the output voltage may exceed the limit the controller can take, and cause damage to the controller. The back EMF voltage is proportional to motor speed. So rider must make sure the downhill speed should not be too fast, and exceed rated motor speed.

Also, rider must be sure that battery is connected to take the charging energy when the vehicle is downhill. The motor may generate more than 500W when the regen braking is on. Such energy must be released to some where, otherwise the controller might be damaged due to accumulated energy.

In summary, MP III has strong torque and power for hill climbing. But riders must make sure the downhill speed not exceed the limit and regen braking energy can be released to avoid controller damage.

We are open for any suggestions to all forum members to help us to improve such situations. Basically all EV will have this same challenging issue.

Thanks in advance.


 
 

[Sanfrancisco]

Thank you for your post.


A. What happens to regenerative breaking  energy at speeds at which Magic Pie generates lower voltage that the voltage of the battery?  Where does it go? A fet or coil heat?

B. I am wondering if possible failures may be attributed to the initial spike
In voltage at the moment the breaks are applied rather than the actusl total energy released.

[GoldenMotor]

We have carried out extensive testing on regerative braking  when the vehicle is moving downhill or slope, below are findings:

1. Regenerative braking will re-charge battery pack if the battery pack is connected to controller, and BMS (battery management system) does not prevent such back current from motor as a generator. BMS used in Golden Motor's battery pack allows such re-charging. If you are using other brands of battery packs, make sure the BMS used supports regenerative braking current, otherwise it may cause damage to the controller when the regen braking voltage is higher than 72Vdc, about 60km/h downhill speed. That is the maximum speed allowed for downhill riding. If the BMS allows such re-charging, the recharging volatge is well below 70Vdc, and energy produce by motor goes into battery pack.

2. If you remove battery pack, or disconnected it from motor controller, please don't pedal your bike too fast and cause high back EMF voltage which may damage motor controller. So the maximum safe back EMF voltage is 60Vdc, or 56km/h.

3. If you use Golden Motor's battery pack and connected with motor and controller, the maximum downhill speed is about 65km/h, if the speed is fast than this limit, back EMF voltage may damage motor controller.

Please ride your ebike safely!