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Old 04-08-2014, 02:03 PM   #6424 (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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I hate to nickel and dime you beta testers, but here goes:
You guys will need 3 pieces of at least 3 foot, 2 gauge cable. Each pieces goes with its very own IGBT/current sensor to the motor. They need to be 3 feet long each, since 2 gauge cable has a voltage drop of about 0.2v at 400amp through 3 feet of cable. That will help with current sharing of the IGBTs. If one IGBT attempts to be a current hog, his cable will say "Oh no you di'ent!", and have a larger voltage drop, causing less current to go through that IGBT, bringing that naughty child back in line with his other 2 brothers.

So, that's 9 feet of 2 gauge cable per person. Now is a mounting question. Do you guys want to just bolt the 3 cables right to the motor? Or bolt them to a big fat 0000 cable (which is about the same cross sectional area as 3 2gauge cables), which gets bolted to the motor? I don't know how close your motor is to the controller.

I should probably get the 2 gauge cable, so I can mount a current sensor to each one, but that step isn't rocket science and you could do it too. But I would like to test each controller before mailing it out!

All this to say, I need 2 gauge cable! and I have no more money left. LOL.

3 kits * 9 feet each is... (pulls out calculator)... 27 feet!

And... to add insult to injury...

Now, for connecting B+ and B-. How about 2 pieces of 1 foot, 2gauge cable for B+, and 2 pieces for B-. I need to spread the current across the capacitor, I think, since there are so many tabs. I don't want to have a single connection point, since the tabs aren't super thick. That makes for 4 more feet of 2 gauge cable per person. So, 13 feet per person... And 4 more lugs per person... The battery current is sure to be smaller than the motor current, so I was thinking 2 cables of 2 gauge is probably OK. Does anyone have batteries that can sustain over 1000 amps?

So, I need 30 lugs, and 40 feet of 2gauge cable.

(if you want to get your own cable, or can find 40 feet, let me know)
Welding Cable 2 AWG 50

ONE ORDER OF THESE: (it makes for an extra 10 left over. If you can find 30 lugs for sale, let me know)
20 2 Gauge 2 AWG x 5 16 in Tinned Copper Lug Battery Cable Connector Terminal | eBay

And then ONE ORDER OF SMALLER HOLE LUGS. Because those capacitor screws are pretty small.

The last part is the end caps. I haven't gotten that yet either. I was thinking 1/4" or thicker of some plasticky sort of material. I hate this part of controller making. The dang enclosure, and interface to the outside world.


EDIT: Or maybe several 2 gauge cables go to a single lug output that's super big and fat. I don't have a way to crimp 0000 lugs though.
kits and boards

Last edited by MPaulHolmes; 04-08-2014 at 02:55 PM..
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