[Motor31]

Ron,

Sorry I missed your post and took so long getting back to you.
It's simple. Go to the auto store and get a couple battery extension cables. They will have a loop on each end to fit over the battery terminals.

First isolate the battery by pushing in the disconnect switch in the jack switch box. Disconnect the ground cable from the battery to the trailer breaking the circuit. Connect the extra cables you just bought positive to positive and negative to negative. This puts the batteries in parallel rather than series. In series you would have 24 volts so make sure it's + to + and - to - when hooking up. In any case confirm voltage with a multi meter before connecting the last ground cable back to the trailer.

I also took the ground cable going to the trailer and moved it so it connects to the second battery rather than leaving it on the original one. That just makes it easier to make the load and charge equal to both batteries rather than going to one first then the other.

This gives you 12 volts but double the amp hours since both batteries are being used simultaneously. That makes the load less on each one when used so they do not get discharged as deeply as if there were only one battery. If one battery should drop a cell and go bad, I can disconnect it from the bank and still have 12 volts for the hydraulics to get on the road.

So far the same batteries have been working on our rig since Aug of 05 when we got the trailer and I installed the second one. I can check each independently by removing the ground cable from one. Then I use my multimeter to check the charge status of each battery. In my case they have been within 1/10 of a volt of each other.

I check the batteries each quarter year (we are full timers) for water and terminal cleanliness. No big deal and takes just a few minutes using a mirror and flashlight to look into the cells. I do not dismount them from the tray for this. If one battery does go bad I will replace both of them at the same time.