Wire gauge recommendation

johnm1 wrote:
To get the most efficent charging to my batteries, with cost kept in mind, what wire gauge should I use between the batteries and charger?

I have a pair of 6v gc batteries.
They're about 12-15 feet from the charger.
I have a Boondocker 75A charger.
Currently have 6awg wire with very good crimped battery lugs.

Thanks

Crunching the numbers 14.6 volts 75 amps 14 foot (28 total using 6awg) shows a voltage drop of 5.68% (.83 volts) adding a 4awg to the 6awg would a bit larger then 2/0 awg and a voltage drop of 1.10% (.16).
It would likely be cheaper and more effective to move the converter. Can you?

What Instructor is quoting apply to household wiring, where there is not much heat allowed.
You might be surprised that on lot of cars starter wire is #6 and carries 400 amp. But then starter is short duty and some heat on the engine is not a problem.
When running #3 wire is always an option, I wold just touch the wires and connectors during charging. Or better yet, get one of those infra-red thermometers. By buying one with laser pointer you will have new toy for the cat as well .

As I recall, the minimum size wire for 75A is 3awg,and that's the max for 3awg. I'd think that a 2awg, good to up to 94A would give you a better safety margin.