battery wires

If you need to replace 3 then you should replace 4, unless that 4th one is brand new- but you said 'last year.'

Take a picture of the wiring *before* disconnecting anything. It will save you a ton of guessing later.

I've always heard it was best to have a matched set of batteries to avoid problems in the long run. I'd replace all of them. Take a picture with your phone of how they're wired before you begin taking anything loose. They should be wired as two pairs in series. The positive on one battery goes to the negative on the second one. You will get 12v from that set. Do the same for the other set. Then both sets are wired in parallel so the 12v from the two pairs stays the same. That doubles the amperage available. Take a picture and then make a drawing of what's in the picture. Label the wires. Label makers aren't real expensive.

One older battery in a set will drag the others down. Spend the extra bucks and replace all four. In a general sense you can mix old and new IF you use same brand, same aH and the older batteries are in good condition.

Put a battery watering system on them while you got them out. Flow-Rite is one, at Amazon or auto parts store. Simple to install and use. I water mine once per month.

Not knowing how much dry camping you do go with the GC-2 from Costco/Interstate with 200 aH each, about $100 each. Lots of dry camping and the deeper pockets you might want to spring for the Trojan T-105's at 225 aH. Usually turn on generator in the AM for coffee and the microwave and leave it on for 2-3 hours.

We do about 2-3 days at a time, residential fridge, temps down to mid to upper 30's and the batteries last overnight with furnace use at 60°, usual TV and LED lights.

RedRollingRoadblock wrote:
One older battery in a set will drag the others down.

Normally I'd blast you for that myth.. but in this case.. not so much.

The problem with replacing just one battery in a pair of 6V is best describe like this:

Would you buy a 12 volt battery where 3 of the cells were brand new and the other 3 were say 2 years old?

Well.. the O.P. Did just that.

Likewisde would you want say half Excide half East Penn battery

Or half 210 amp hour half 230


When you put two batteries in SERIES it is important they be same/same/same.. Basically twins of each other.

Now batteries in parallel you can mix and match no problem older/newer, bigger/smaller/ different brands for the most part does not matter so long as they are all the same type (Flooded wet, Maintenance Free, AGM)

But for batteries in series: Same/Same/Same

Each pair of 6 volt batteries becomes (Not magically) a single 12 volt when you hook up that jumper wire between them.

A battery is a collection of cells. They need not all be in the same case.

He's gone

Label the wires, and take a picture before you disconnect them.