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Old 07-28-2010, 12:19 AM   #3589 (permalink)
MPaulHolmes's Avatar
Join Date: Feb 2008
Location: Maricopa, AZ (sort of. Actually outside of town)
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Michael's Electric Beetle - '71 Volkswagen Superbeetle 500000
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Oh man, that's not good.

You hit the accelerator, and the ammeter went really high for a few seconds, but nothing blew up? So, when you took your foot off the throttle, you have a contactor that opens? That must be what kept it from blowing up. My guess is that at least 1 mosfet failed shorted when you hit the throttle, but the legs didn't have a chance to blow up because you opened the contactor soon enough. Then the next time you hit the throttle, since at least one mosfet was failed shorted (it looks like all were failed shorted), it was like a short circuit across 120v, so thousands of amps all at once, which would vaporise the legs. But why would 120v cause the mosfets to fail?

You had said there was a loose connection before. What was that? Was it one of the solder joints? If the front end was almost lifting up at 60 volts, that didn't sound right either. It should have been smooth acceleration. I wonder if there was a problem even at the lower voltage. Was there any time that the 12v battery shared a ground with the full pack voltage?

The hardware overcurrent protection wasn't working I think because the mosfets had failed already, so it wouldn't have mattered if the mosfet driver was disabled.

Does anyone have any ideas as to what could cause this? Ben had problems with his controller from moisture. He ended up baking the control board and sealing it in really well. It was quite a while ago that you got it. Could it have gotten some moisture in it sitting out in bad weather for several months do you think? I'm just making stupid guesses at this point.

Maybe I did a bad solder joint somewhere. It was one of the first few I made, before I learned to solder very well. Even now I'm still not very good.
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