Help Installing Trailer Charge Wire

[Carl V]

Originally Posted by Byron Kinnaman

2005 Dakota with factory tow package.
direct from the battery to fuse block, through a 30amp fuse to 7 pin connector. 10 awg wire teflon (cross link) insulation.
No diode, or other items. When the trailer is plugged in both the truck battery and trailer battery are connected together.

Exact same setup here. Except I'm using a relay as an isolator, which is controlled by the ignition key.
Relay is closed when the key is an ON.
Relay is open when key is at START or OFF.
It's a continuous-duty relay, sold specifically for this.

On the trailer side, from the 7-pin connector I'm running 6 awg wires direct to the trailer battery (fused at the positive also).
I'm using 6 awg since I was able to get some for cheap, otherwise 8 awg would have worked good ok.

[Darral T.]

My '99 Frontier/2010 13' Scamp truck wiring setup I did myself (thanks to etrailer.com kits/etc.) I ran a 10ga wire w/40A breaker to the truck's 7-pin. With that wire/pin, I run my small Dometic 1.9 Cu Ft fridge on 12v while on the road maintaining 40+ deg. I've pulled as much as 6-7 hours with this setup with NO problems- even stopping to eat breakfast with the trailer/tow still connected and the fridge still on 12V! For what ever reason, not all can do this but it's worked for me. So 10ga has been MORE than enough wire for me.

FWIW, my ole '99 Nissan Frontier with a 4-cyl engine has the stock alternator and is still the original one from the factory.

[steve dunham]

Originally Posted by aznative

If you have a large gauge wire like 4,6,etc compared to a 10 or 12 it will charge the same exact time. Larger wire does not necessarily mean faster charge. It all depends if the smaller gauge wire will not fail like melt or blow fuses. So if the smaller gauge wire won't fail then it will charge at the same rate as larger gauge wire. The resistance from the batteries is what dictates charging current.
Yes if the charge line is 12.6 volts the secondary battery can get a slightly higher charge then line but not much. I'm sure there is an equation for this but I'd rather not ask.

A #12 AWG solid copper wire can carry approx 150 amps before the wire melts. The main problem with DC is voltage drop .
Due to the American belief that bigger is better , people run overly large charge wires at a much greater cost with little or no gain.
A #10 charge wire will allow you to charge your trailer battery.
There are many more limiting factors and increasing the wire size is not the only answer.

[Radar1]

Originally Posted by aznative

...Then on the trailer side I am going to use 10 gauge again with no fuse to the trailer battery.
TOAD-CHARGE Dinghy Vehicle Battery Charger/Maintainer

I believe it's important to have a fuse at the trailer battery also. Imagine getting a short in your wiring, and the fuse on the tow vehicle blows. You have cut off the current from your tow vehicle battery, but since the cause of the short is still there, your trailer battery will now be providing power back to that same shorted circuit.

[gordon2]

Originally Posted by Radar1

I believe it's important to have a fuse at the trailer battery also. ...

I'm tempted to say DUHHH! LOL

Anytime you add a charge wire, brake controller, etc and are adding wiring going to the tug's battery, it should be fused as close to the battery as physically possible. Something like this is not a bad way to do it.

https://www.westmarine.com/buy/blue-...lock--16932840

[steve dunham]

All wiring should have overcurrent protection at the source of power. One of the only times you can over fuse a conductor is when it feeds a fire suppression pump . If the building is on fire you don't care if the wire or the pump burns up because that's the least of your problems.