Battery Failing Prematurely

[Old_Islander]

I bought a 100 amp hour deep cycle battery about 18 months ago, and it seems to be failing. It will only remain above 12 volts in the camper, for about 12 to 14 hours, with normal camper use. When it was new, it would last for 2 or more days. This is without using the forced air furnace, but water pump, lights, (and all the background circuits -- alarms and so forth...) I generally run the happijacs and slide-out with the truck engine running.

I charged -- then disconnected the battery last fall -- in April it was still very close to 13 volts, so it held it's charge well over winter. I'm wondering if I have a short somewhere in the camper that is sucking the battery down?

How do you measure the resistance of the camper's electrical system? I have a pretty good ohm meter, but don't know what settings to use, or what to look for. I guess I'd check the various systems of the camper, by measuring resistance at the battery cables, by removing all the fuses, and then inserting them one by one, and checking resistance for each?

Is there a definitive test for batteries, that will measure their ability to last under load?

Any advice will be appreciated.

[BFL13]

"I charged -- then disconnected the battery last fall -- in April it was still very close to 13 volts, so it held it's charge well over winter. I'm wondering if I have a short somewhere in the camper that is sucking the battery down?"

It "held its charge" with no load on it, but collapses under a load. Usually means the battery is sulphated, as noted above re previous undercharging.

It is still possible there is an unknown draw in the camper. Your Happijac problem might be related. Is it possible for the jacks' power unit to be stuck "on" when you think it is turned off?

[Lwiddis]

“Solar makes a good maintainer getting the batts to 14.6v daily charge”

You bet it does and my “maintainer” is a small solar panel and WindyNation 10 amp twenty dollar weather proof PWM controller.

[red31]

What is the charge profile being used to charge?
repetitive undercharge is what I suspect from here 😉

For now take it to a auto parts store that does a free charge/test.
Find the makers charge profile and mimic!

Solar makes a good maintainer getting the batts to 14.6v daily charge.

[2oldman]

What brand of battery?

[MrWizard]

Do you have a 3 way fridge, rare but still around
Fridge on 12v instead of lp will suck a battery like a vampire
Left a light on in the storage bay?
Emergency brake pin pulled out ?
Water pump cycles a lot ?

[amxpress]

You might consider performing a parasitic draw test on the system using your multi meter. All items turned off, connect your ammeter in series between the Negative post and the Negative battery terminal. I don’t know what an acceptable draw is on your rig, perhaps someone with a similar set up can tell you. It is difficult to use an Ohmeter to test your system, but you can perform Voltage drop tests to check for poor connectors, corrosion, etc. But that’s another “how to”story.