Thursday, September 08, 2011

1000 Amps vs 30 amp fuse

After a recent work session, I forgot to reconnect the 12V signal to my front contactor, which is a backup unit that disconnects the pack when the key is switched off, but bypassed with a 30 amp ATO fuse in order to allow battery charging. Well, the car will drive just fine around the neighborhood at under 30 amps, but here's what happens when you stomp the go pedal!

The paint damage is permanent, but luckily, the overvolted body didn't blow my instruments.

And yes, Mr. Anonymous, I was using a dramatically under-rated fuse, having allowed a quick fix to remain too long, and this incident does demonstrate that any old fuse will carry the rated amps, but only a properly-rated one will safely interrupt too many! There's a nice sand-filled cartridge in it's place now.

1 comment:

Anonymous said...

The problem was the voltage, not the current. It appears you were using a regular automotive blade fuse. These are rated to 32 volts. They can't break high voltages without nasty arcing, as you found out. A properly rated high voltage DC fuse would quickly and quietly interrupt 1000amps with no drama.