Trouble with Auxilary batteries

cgmartine wrote:
also a trickle charger/maintainer (not a battery charger).

This is unnecessarily confusing.

You should never use anything labeled "trickle charger" in an unattended application.

You need a small fully automatic tender type battery charger.

If it costs less than $10, it probably isn't appropriate.
Reasonably good ones can be had in the $20-$30 range; sometimes a bit less.

Rather than a single 12 volt battery, I would go with two 6 volt Trojan T-105 batteries, and also a trickle charger/maintainer (not a battery charger).

3 in the RV wrote:
So, I had the batteries load tested and they are shot.
Recommendations on what to replace them with?
Also, any thoughts about hooking up a battery maintainer while the RV is just stored or how to help the house batteries last longer than a year. I think this is all that this set lasted for.

What sort of camping do you tend to do? If you're camping without hookups for relatively long times (more than an overnight or possibly a weekend), you probably want as much battery capacity as you can reasonably get. Frequently this would be a pair of 6V GC2 batteries connected in series, assuming you have sufficient space (including height) for them.

If you only camp with hookups, a single 12V battery should be entirely sufficient.

A good multistage converter, such as a PD 92xx or 46xx series, will not destroy batteries if left connected and powered up in storage. Many RVs unfortunately don't come from the factory with a good multistage converter. A solar setup with a decent charge controller will likewise keep the batteries in good shape assuming you have light where you store the RV. A standalone charger/maintainer could also be used, though not all such devices are particularly good.

If no charger is used, the batteries must be disconnected (often the disconnect switch doesn't remove every load from the battery) and can reasonably be expected to sit without losing too much charge due to self-discharge for times varying between a week or two or three (in hot weather) to a year or more (in very cold weather). The rate of self-discharge is strongly correlated with temperature.

Sam Spade wrote:
No they won't. Especially if they are "deep cycle" type.

Simply discharging a wet cell battery doesn't cause it any damage.....unless you get the voltage WAY down, like maybe to 3 volts.

What causes the damage is discharging it and then LEAVING IT LIKE THAT for an extended period of time, like weeks. A few days at 12.0 volts should be no problem.

Sam ... well put ... and not commonly known!

So, I had the batteries load tested and they are shot.
Recommendations on what to replace them with?
Also, any thoughts about hooking up a battery maintainer while the RV is just stored or how to help the house batteries last longer than a year. I think this is all that this set lasted for.

TreeSeeker wrote:

You should never let your batteries get below 12.2v or they will suffer permanent damage.

No they won't. Especially if they are "deep cycle" type.

Simply discharging a wet cell battery doesn't cause it any damage.....unless you get the voltage WAY down, like maybe to 3 volts.

What causes the damage is discharging it and then LEAVING IT LIKE THAT for an extended period of time, like weeks. A few days at 12.0 volts should be no problem.

As batteries age and are used, the plates inside become coated with sulphation.
When this develops, they lose capacity to crank the generator even though they may show over 13 volts while plugged into shore power or after charging with a car charger. Our two T-105 6-volt golf cart batteries lasted around 10 years, I replaced them with equivalent cheaper US brand batteries and replaced the original converter/charger with a modern Progressive Dynamics 45 amp multi-level charger which won't overcharge batteries and boil out electrolyte.
RV batteries that are not kept charged and electrolyte levels checked and maintained don't last as long as those that are.

...12.0 is about 50 percent discharged.

Actually, 12.2 volts is 50% discharged. 12.0 is 75% discharged.

You should never let your batteries get below 12.2v or they will suffer permanent damage.

Yes,Leave it in ON position. If you shut it off, converter/charger can't charge house battery and power the lights and 12 volt DC appliance controls, etc.

3 in the RV wrote:
So I checked voltage and I have 10.46 on each of the batteries. Sounds dead, right? When I turn on one little ceiling light and the little porch light it drops to 9.95. However, when put on the battery charger (completely out of RV) they appeared to charge easily and indicated a full charge. (Obviously not correct).

Most likely: Your batteries are totally shot. Maybe the set in the truck too.

Normal no-load float is 12.6-12.8 at 100 percent charged.
12.0 is about 50 percent discharged.

It takes about 13.4 to give them any significant charge at all.
A healthy charge needs above 14.

You probably should try a different charger but don't get your hopes up too high. You have checked the liquid level.....right ??

After you get new batteries, you need to check charging voltages again.