What gauge wire for batteries, motor, controller?

Hi James,
In your design, 2/0 welding cable is more than fine for the feed cables, 4/0 can be used for the motor cables. (the motor cables can see higher current through them than the battery cable because the voltage to the motor is varied by the controller, except at full throttle) We have used 1/0 cable throughout without any heating at all, even in liquid tite conduit. Generally you want to use the large cable just to limit voltage drop through the cable for the short periods of time at high current, as heating is not an issue.
I would use welding cable, it is much more flexible with a lot of finer strands. I would also just crimp them with a correct sized crimper.
We have tried to get the NEC and cable organizations to give a recommendation for cable size for EV's , but no one will commit to anything, although I have read that there will be an official answer coming out possibly next year.
Mike
www.EV-propulsion.com

Would definitely advise not to solder. A weak soldering point will cause a lot of resistance/heat and provide a very easy point of failure. Crimping is much more reliable.

I have a very similar set up with modly 4/0 wire and a few shorter connections of 2/0. The cables seem to work fine. I have both hammer crimped and soldered the connections in both of my vehicles and have not had any problems. My truck has more than 30,000 miles on the wires so for me both seems to work. I agree I would not solder only.

I prefer the flexibility of welding cable, less likely to fatigue and break internally from years of fussing with the components.

+1 on crimping, I agree soldering is asking for trouble.. especially once the cable is hot enough you get solder wicking and the last 4" of the cable is solid. No good.

Don't forget the NO-OX.