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Old 06-28-2010, 12:01 AM   #3492 (permalink)
reissmachinist
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Join Date: Jan 2010
Location: Omaha, Nebraska
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OH NO The Magic Smoke Has Escaped

I had been running on 9 12 volt batteries for a week or two and getting to
like this EV thing. I took my dad out for lunch in it twice, He was impressed
with the performance.
Friday, I loaded up a bunch of junk batteries and traded them for 6 good used
batteries with a 30 day guarantee and $54. So now I had 15 batteries and 180,195
volts to the armature. It did have the higher rated mosfets, diodes and capacitors.
I eased out of the driveway, down the alley and into the street. It seemed to have
a little more pep. I gave it a little more throttle and started to accelerate.
It did for a short distance and then seemed to accelerate abruptly, more than I had
commanded and there was a sound like popcorn popping fast. I pushed in the
clutch, hit the main disconnect breaker and coasted to a stop.
Because in this short ride I hadn't stepped on the throttle hard, I think the failure
was probably voltage related instead of too much amperage.
The damage is the worst at one end of the board, burning it away between the B+and B- bus bars.


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i dot imgur dot comslash MxrUK dot jpg

i dot imgur dot com slash MxrUK dot jpg

i dot imgur dot com slash MxrUK dot jpg

Sorry about that, I don't have enough posts to post links.

I took it all apart and found the aluminium bar and insulator tape under the mosfets OK.
I cleaned the control board and powered it up, the LED's both lit up solid.
The mosfets were $7 in January and now they are $12. Digi-Key has 124 of them.
Next build maybe I will stay with 144 volts.
Hot and Humid here!
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MPaulHolmes (06-28-2010)