what gauge wire between two batteries?

[raztec]

I'm adding a second AGM battery to my truck camper.

It's going to be under the bench seat in the back on the other side from the 1st battery. So their distance will be about at least 10-12 feet from each other.

What gauge wire should I use between the batteries?

Also, as it will be a Trojan AGM battery, does it need to have a plastic container or be vented in any way?

Thanks a bunch for your replies,
Raz

[raztec]

I'm only using it to run the fan, charge my computer and electronics primarily.
In the winter, the furnace will be running on occasion.
And I may run an external water pump to fill my tank.

But no t.v, a/c or microwave for sure.

Thanks
R

[MrWizard]

you want 'welding cable' not house wire
you can tie welding cable into a figure eight

with only ONE additional battery i think you could use 1/0 ( 1 aught ) cable and be fine

its voltage drop between batteries under heavy loads (aka INVERTER) like MW or coffee maker
you want to have as little voltage drop as possible, and equalize the current drain AKA amps to be as close as possible

[DrewE]

What sorts of loads do you have on the batteries? If there are no large loads (like a sizable inverter, for example), you'll definitely be fine with such wire, and could probably get away with somewhat smaller. Wire sizing is dependent on the current that will flow.

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.

[2oldman]

Wire size depends on the largest amp draw you expect from your batteries.

[raztec]

Thanks for the info.
My batteries are the larger 31 series Trojan Deep Cycle AGM.
I'll have to see if they both will fit there.
That will require a little more re-wiring than I had hoped for and much bigger holes.

If I do end up using 2/0 gauge wire, will I be alright with that sort of distance between the two batteries?

Thanks
Raz

[westend]

Also, I presume the batteries would be discharged evenly and should be hooked up in parallel. Any reason to have them swap positions every so often?

This is the whole issue with batteries in the same circuit but in different locations, the discharge and charge will be unequal unless large cable is used.

FWIW, I have two banks of batteries and one bank is located 6' from the distribution and charging location. The other bank is within 1'. I chose to use 1/0 cable for the farther location and all is functioning correctly.
If you only use small draw devices like lights and water pumps, etc. you can get by with smaller wire. You will also need to budget time for charging so that both batteries get an equal charge.
There is no reason I can think of to swap locations if both batteries are the same.

Edit: In this Northstar Laredo, two batteries are located next to each other:

If it's at all possible to locate your batteries in the same compartment, it would be the most advantageous. Maybe it's possible to build a shelf to accommodate the second battery?

[raztec]

I was told by Rex, the head guy at Northstar, that's where a lot of people put the second battery.

I was under the assumption that 6 gauge would be ok, but thanks for the heads up.
A 2/0 is awfully thick and will require much bigger holes and not sure how well it can bend around tight corners. Can I get away with smaller?

Also, I presume the batteries would be discharged evenly and should be hooked up in parallel. Any reason to have them swap positions every so often?

Thanks

[westend]

That's not the best situation but I would use 2/0 at a minimum. Is there no possibility of installing close to the original battery? You do know they can be used when on their side?