Wire gauge recommendation

[johnm1]

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

[Kayteg1]

Other issue will be allowable charging current for the batteries.
Rule of thumb would be about 20 amp, so 75amp might be killing current.

[grizzzman]

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?

[Kayteg1]

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 .

[Fire_Instructor]

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.