dfletch wrote:
....The usual #10 wire reduce current flow to the distant batteries and signal the regulator "charged battery". Depending on how many batteries are being charged and how far away, I wouldn't consider anything less than a #8 wire with #6 more ideal.
In years past I was able to purchase some "surplus" welding cable that made a great towed vehicle battery charge wire. Only needed one as between ball and equalizer contact there was sufficient ground to carry the other half of the circuit.
I love your recommendation (minimum = 8-AWG, ideal = 6-AWG). But even
an upgrade to genuine #10 would provide a huge improvement in most vehicles: Nearly all Manufacturers claim the entire Tow Vehicle to be "Chassis Wiring", and use
thin wire to connect from the Trailer plug/socket (under the dashboard) back to the Bargeman connector. They
don't use wire which could meet the NEC for house wiring. NEC is concerned with voltage drop, Car/Truck manufacturers merely want to avoid risk of fire - and save money.
Don't be mislead by the 30A fuse size! In my own Toyota 4Runner, 2007, the "Trailer Battery Charge Wire" was definitely not bigger than #14. I was very surprised to see that. In a fairly new GM SUV, another Trailer owner I know found the same situation (THIN wire installed at the factory), and he upgraded to #8. A 3rd guy I know, with a big pickup, saw the same thing - and added a new #10 in parallel with the factory wiring.
#10 is not "the usual" wire size from the factory. It's not even #12. People who have done this upgrade are finding #14, and sometimes even #16.
