Grounding Batteries in Parallel

[Dankwest]

Situation: two 12v 100ah deep cycle group 29 batteries mounted lengthwise, wiring in parallel.

Is it necessary to connect ground wire(s) from the factory trailer wiring to 2nd battery OR can the ground wire just be connected to battery #1? Does it matter where those ground wires are grounded?

I realize bat 1 positive to bat 2 positive, and bat 1 negative to bat 2 negative for the parallel cabling connection.

And this would also apply to making a connection with my Externally located inverter (Cables = positive to bat 1 positive, negative to bat 2 negative).

I'm trying to avoid extending/splicing the factory negative cables to be able to make the connection on battery #2. as the factory installed wiring is too short.

[CHICKDOE]

It is only necessary to have one ground wire from either battery negative terminal to ground for a parallel configuration. Just use the one that came from the factory.

[Chuck_S]

The negative pole of the battery goes to the trailer frame (ground).

Connect them in parallel like this to equalize loads on the batteries. Only makes a tiny difference but with all the 12v appliances being dumped into campers these days every amphour counts.



-- Chuck