Something smells
- Thread starter nalu808
- Start date
nalu808 said:
That's what happens when you reverse battery polarity.
Unfortunatley that's been reported before when connecting batteries when not fully awake, not feeling well, not paying attention, etc.
Sometimes the controller survives this, only needing certain parts replaced, but often it does not.
The big problem you ahve is teh severe damage to the board itself in that area. If it has not destroyed the traces there, you can carefully and slowly brush away the burned plastic coating in the area and examine the copper traces left behind. If they appear to be intact, and dont' suddenly end without going anywhere, you can run wires from one end to the other (where the traces connect to components) to replace them. If they have burned thru and you can't tell where they went, that's hard to do. Some will be obvious, but some may not be.
Sometimes the PCB damage is so bad it wont' even support components or wires attached to it, and then you have to get creative in routing wires in place of it, and mounting components so they still do their jobs and cant' move, but can disspate heat correctly, etc., (all things the PCB was doing before).
The parts I have replaced on the fixable ones people have sent me:
--all capacitors (the cans) on the main battery bus. These are polarized and easily damaged if you reverse polarity (even if they don't look damaged, they can be damaged or even non-functional after this). The biggest ones, and sometimes any of the next smallest size that are near that end or along the FETs.
--Shunts (the two thick "wires" that look "burned"). These may be undamaged despite appearances, but I have had some that were damaged in a way that caused the controller to read current incorrectly (too high, so it began limiting before it should, and the bike had less power). They're too low a resistance for you to measure to test them; usually in the milliohm range, but exactly what yours were I don't know. If your controller had it's shunt resistance labelled (rare) then you can do the math for two parallel resistors to get that value to reverse that number inot the separate shunts.
If you need to replace them, you can take a pair out of another similar controller and it will probably work, though it may not respond exactly like it did before (more or less power). You can also order Manganin wire to make some from, if you can't find Manganin shunts of the right size, value, etc.,
--FETs. These are all the parts under those clips along the metal bar. If any of them is damaged, they probably all are. This is a basic functionality test you can do:
https://ebikes.ca/documents/BlownMosfets.pdf
if any comes up shorted or damaged, I'd replace all of them, not just the ones on that phase. (others might pass this basic test but then fail under load and then take out their gate drivers or even the MCU chip, and then the controller is junk).
If the keyswitch or ignition was not turned on or connected at the time (or it has a display or other button that "turns it on"), then that's usually the limit of the damage.
If it is wired to be on all the time the battery is connected, or the keyswitch/ignition was on, then also these:
--LM317; this is probably the part sticking up out of the board at the very far right of the second picture, down in the lower right corner. It looks like a FET, but isn't. Since there is no burning on the fat resistor to the left of it, it's probably not damaged. But if you get no 5v after the repair, you can check the LM317.
Typically if it's anything other than those parts, the controller is toast; if the low voltage stuff appears ok then I may save it for parts for fixing others.
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