what gauge wire between two batteries?

2oldman wrote:
Wire size depends on the largest amp draw you expect from your batteries.

And the length of the run.
Has nothing to do with the potential, only the load...and proper fuse size/location.
Check out www.bcae1.com. It's geared towards car audio, but same principles.
Good resource.
Quick guess is a #4 would be sufficient based on lengthy and current.
I'm sure the person who said 2/0 guage meant 2 gauge.

Balanced wiring provides for the longest battery life for both charging and discharging. The current battery will supply or charge the most amps. This is due to the higher wire resistance to the remote battery. For your application balanced wiring doesn't seem practical so just use the largest wire possible.

Good lord id hope that the charger is stronger than 2 to 6 amps. Are you talking about engine charging or shore power? If shore charging it's usually more like 50 amps (see that gizmo I linked to in a precious response). If engine, some systems use a cheesy relay system that simply connects the two battery banks when the engine is running (or more accurately when the key is turned). Mine has a dual alternator that charges each at around 50 amps.

I use and love the trimetric battery monitor, which tells me the exact charging rate:

http://www.solar-electric.com/trtmbamosy1.html?gclid=CMKA_Ou2r80CFVUkgQodQtwE9Q

Thanks for link. This seems important for charging only and not for draw coming off batteries correct? Also, how important is it for a truck campers charging system? My understanding is that truck campers have a very low amp (2-6) charger.

DrewE wrote:
...

Do be careful to connect the batteries up in a balanced fashion and to do your best to ensure that the two interconnecting cables are the same length and gauge. Wiring them to be balanced means having the positive connection to the camper's systems at one battery and the ground connection at the opposite battery, so that current to or from either battery will travel through exactly one of the two interconnecting leads before getting to the rest of the world.

The batteries are identical, 31 grp. Trojan AGM. But the distance from their leads to the rest of the world is obviously different, as they are 10feet apart. I'll be using 4 gauge welding cable.

I was planning on simply going from the + to + and - to - of one batter to the other.

I'll still do that, but since the original battery in the box, has the ground (I presume), are you suggesting I keep it's negative connection as the ground and use the positive of the new battery in the further box as the positive which will connect to the rest of the world?

Trying to clarify this before the install tomorrow.

Thanks
Raz

my brother had a battery store and he told me to use the biggest wire you can work with. big wire less resistance.

On a sidenote I had to rebuild the charging system in my new-to-me RV since, being a 1989, it just wasn't working very well. I went with one of these:

https://www.amazon.com/Powermax-Supply-Converter-Charger-Pm3-55/dp/B00F8MC440

Very handy gizmo: connect it to your batteries and they charge at 55 amps when the batteries are low. Actually I measured the rate at 45 amps, but still, plenty. And its a smart charger so it slows down when the batteries are nearing fully charged, and stops completely when they're charged. Great chargers. Basically the same sort of unit that most modern RVs have.

> It's not recommended to use the battery charger on the Honda. It's low amps and unregulated.

+1 to that. I think its only 10 amps, basically useless as a charger. Just plug your RV into the Honda and let it charge your batteries.

1. I'd venture to say a week.
2. Ok, figuring 102 usable AH before 50% depletion, you need to put back around 110ah.

Using the battery cable from the Honda (8amps), that's 110/8= 14 hours. Using your converter at around 30a, plus absorb time, around 4-6 hours, minimum.

It's not recommended to use the battery charger on the Honda. It's low amps and unregulated.