Quote:
Originally Posted by electrowizard
And the current spec: according to the datasheet you can pulse up to 700A with a small (<100us) pulse. My starter draws 380A, and my pulses were only 2us wide at 16kHz. The mosfet was cold to the touch when it died silently 2 seconds later, and the starter drove to full speed until I pulled the battery wire.
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This is fun stuff, isn't it? Some things i can think of...
I'd take all datasheet specs with a grain of salt. Even still, I think that 700A pulse rating is for a single pulse, like in a pulse welder or something. I don't think it applies to many thousands of pulses for several seconds. It seems that the rule of thumb is to limit the current to half of the device rating.
Are you sure your starter draws 380A in your setup? that'd be a lot - way more than a single fet of this type can handle. Do you have a way to measure current? Maybe start with a smaller load? like, a radiator fan? or, small resistive heater?
Which bus bars are your caps connected to? They should be connected to B+ and B-, but it almost looks like M- and B-. I cna't really tell from the picture.