Wire Gauge for 2x 6V 220Ah in Series?

[Konvett]

Hi everyone.

My friend has a pop-up trailer and I've been helping him install a solar setup. He bought a couple Renogy panels, a 60A charge controller, and a 12V 200Ah battery. The trailer itself has two 6V 200Ah batteries in series in the front of the trailer. It looks like the wires they're using to connect it to the wiring harness are close to 10 gauge.

I'm curious what gauge wire I should be using to connect these batteries to the charge controller (serving as the alternator since those batteries are charged by the truck). Any advice or input here? I figured the wires on those batteries would have to be closer to 2 or 0.

 

[FilterGuy]

He bought a couple Renogy panels, a 60A charge controller, and a 12V 200Ah battery.

The size of the wire between the controller and the batteries can be viewed in a couple of different ways:

1) The charge controller could produce up to 60A. If we use 60A, the wires would need to be at least 8 AWG .
2) If the panels are less than 360W, the controller will never produce 60A, so he may be able to get away with smaller wires. As an example, if there are two 200W panels, the total wattage would be 400W and the current would be 400/12=33.5A. If he uses the ABYC Standard, 10AWG 80deg C rated wire would be sufficient.

If it is reasonably easy to replace the wire, I would go with 8AWG. If it is hard to replace the wire and the panels are 200W or less, just use the 10AWG.

 

[underdog5004]

In a battery bank, especially lead acid, I want to reduce resistance as much as possible.

In that case, I'd make the wires the next size up from the largest set that connects (inverter?). Since these wires will be so short, I'd probably go with #2 or preferably 2/0 cable. It's overkill, but at least you don't have to worry about it being too small, so close to the battery.

 

[740GLE]

What can the SCC accept for max gauge? Can’t imagine a 60a charger can accept 2/0.

A Victron 60 or 70a charger maxes out at
2awg. Cheaper SCC are probably smaller conductors.

 

[underdog5004]

What can the SCC accept for max gauge? Can’t imagine a 60a charger can accept 2/0.

A Victron 60 or 70a charger maxes out at
2awg. Cheaper SCC are probably smaller conductors.

Oh I misread the question. I use the largest cable possible for scc. For fm80 charge controller, that's #2. 60a probably wants #6 or better. Can use a Polaris plug to tie into larger cables if the scc to battery path is long enough to warrant. Depends on voltage drop.

The point is to minimize resistance and thus heat and voltage drop. Size once, buy once.

I'm not familiar with charging trailer batteries from truck alternator. You may want something other than a charge controller.