I'll answer this myself:
I had a full lipo battery and went down a steep hill in regen mode.
The regen tried to put power back in the battery, the battery didn't want it and something had to go.
This damaged my controller and battery.
Anybody know how to prevent this??
Full Answer from electronic engineer:
Motors that have their windings shorted together turn hard. That's what dynamic braking does, essentially. So maybe your controller is shorted.
Another thing is that whenever power MOSFETs fail due to overheating and/or voltage spikes, they very often fail shorted.
A + B = check to see if the motor turns easily when it's unplugged from the controller. If so, the motor's probably fine.
If the controller is bad, it's probably the power MOSFETs. Rip it open, and trace the motor power wires through case, connector, circuit board, etc., up to the big chips with heatsinks. Find the part number and search the web for data sheets and distributors. Try
http://digikey.com/ for both. If you can find replacements and data, then it MIGHT be worth going forward. See attached datasheets as examples.
See attached Application Note, and refer to Figure 2. The power chips may be electrically arranged as three groups of two. Three will be connected to the (+) rail, and three will be connected to the (-) rail. Each pair will be connected together, and that connection will go to a motor wire. For more info, that App note came from
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1523 Once you have figured out your layout, measure the resistance across similar pins of similarly connected MOSFETs. If they are not the same, you found a problem. The question is how to solve it. There may be other things wrong besides the shorted MOSFETs. I am not familiar with the regenerating drives yet, but I expect that the basic circuit is the same with extra stuff to boost the back EMF above battery voltage.
