[Al Skierkiewicz]

Ryan,
Thanks for the exercise. The main breaker resistance is actually much less than your guess by a factor of 100 though. A new breaker that has never tripped (resulting in some pitting of the contacts) will have a series resistance in the .0005 range (verified at Motorola labs a few years back). The battery is capable of 600 amps at full charge albeit at reduced terminal voltage due to the internal resistance of the battery. I was unclear if you included heat dissipation in the wiring connected to the breaker. I believe that is a sufficient source of heat loss as it increases the surface area exposed to ambient air making the return to ambient for the breaker even less than calculated. It is great to know my hunches are backed up with math. Cool!