Battery problem--replace one? or two?

[David and Jo-Anna]

When we briefly lost power during a storm recently, I thought the DC powered lights seemed a little dim, so I checked the idiot lights on the interior monitor, and it showed the batteries as being only 2/3 charged. Since I had been on shore power for a considerable time before we lost power, I would have expected the batteries to be fully charged. When I checked the batteries themselves, I found that the water level in one of my two house batteries had run low in all six cells, even though the water level was fine in the other battery. OOPS!!

Based on posts I have seen here in the past, I assume that battery is shot, and that keeping that battery will only screw up the charging and operation of the other battery. We're heading to Quartzsite in two weeks, so I want to be sure I have good batteries to get us thru a week of dry camping. I had the two 12v deep cycle marine batteries installed new in our rig when we bought it in April 2007. Can I get away with just replacing the battery that went dry, or would it make sense to buy a new pair of batteries so that they are matched?

And any recommendations on what replacement batteries to get?

[capn chris]

I'm no expert (as you know) but I'd start by filling the low cells w/distilled water. That may be enough to help that battery get back to a full charge. Lot's cheaper than a replacement. I know you've used your rig full-timing, but the battery should last longer than 1-2 years. See what happens. Best regards,

[HamRad]

David and Jo-Anna,

I'd start by filling and charging the battery that was low. Make sure both batteries are full of water. Then simply charge them as you have been. You will quickly know if the low battery is damaged or not. If it is damaged and will no longer hold a charge then I'd definitely replace it. Probably only the one bad one if they are only a little over a year old. If they were 3 years or older I'd probably replace both. And generally when you replace batteries you should do both at the same time.

If you replace just the bad one make certain to replace with the same thing as the remaining battery.

You may want to take this opportunity to go to the 6 volt batteries. I've been very fortunate with my current batteries. Over 3 years ago I replaced my original "deep cycle" 12 volt batteries with a couple of 12 volt deep cycle maintainance free type. Got them while in Q.

But next batteries will be the 6 volt "golf cart" type.

Good luck with your situation.

Dennis

[Ontheroad]

I agree with the previous posts. Try charging and then test.
The best and only way to test a battery is with a hydrometer.
They aren' that expensive (get the turkey baster type) and test each cell.
If the readings are low in any cells after a full charge, then the battery needs replaced.
Before that, though, test the voltage at the batteries while under charge. They should read over 13.5 volds. If not, you have a converter problem.

[stiles watson]

I agree, low water does not mean the battery is shot. If you fill it and it will not hold a charge, then it is shot. A way to check it is to take the battery to any auto store and have them test it under load. Most are able to do that. I have been looking at Optima batteries when replacement is required. They are available at Sam's Club at better prices. They are sealed and operate with new technology rather than lead plates. You can research them online.

[bsmeaton]

Hard decision when you know you are heading to the boonies with no shore power! That's like noticing you had to add 10 lbs of air to one of your tires the morning you are heading out on vacation .

Agree with others above, but I also agree if you are considering replacement there are many alternatives and options. Our two 6-volt golf cart batteries seem bottomless compared to the deep cycles in previous rigs and have my recommendation. I have never looked at the Optima or gel cell, so not sure how they compare in performance.

[David and Jo-Anna]

Thanks for these responses. When I noticed the low water situation yesterday, I filled the low cells with distilled water. Since then, the converter would have been applying a low level charge to the batteries. When we lost power briefly this afternoon, I again checked the idiot lights on the monitor panel, and they were showing the charge level at only the 2/3 level. I don't have a hydrometer here, and the nearest hardware store is 150 miles away. Any other thing I can do now to tell if the one battery is shot?

My options now seem to be to stop off in Phoenix in two weeks on my way to Quartzsite and pick up one or two batteries, or wait until we get to Q and go shopping there. Dennis, what are the shopping opportunities at Q for buying batteries--is there good selection and reasonable prices?

[H. John Kohl]

You can take the good battery off line and see how well the "bad one" responds. If your inverter has only been trickle charging the whole time it will not charge that battery.

[hookman]

Remember your batteries are only as good as the weakest one. If the one is taken a full charge and is fairly new you could get by with one but normally you replace both.

[stiles watson]

David, do you have a multimeter? Do you have an independent charger? Just for reference, I carry both. The charger is an auto charger with trickle charge (so it won't boil over). It is about 8" X 6" X 5", so it takes very little space. The multimeter fits in my shirt pocket. I think both can be bought from Harbor Freight at a minimum of expense and they ship over night. Orders can be made from their online store if you are not close to a Sears or Radio Shack.

PS: After posting, I checked Harbor Freight online. They also have a 6volt/12volt battery load tester that weighs about 2.5 lbs. The load tester will tell you if it is ok.

Check at:
http://www.harborfreight.com/cpi/cta...emnumber=93784

[simonsrf]

David,

Go to that funky hardware store in Ajo. They should have a hydrometer there, but if not, try the auto parts store around the corner. Hydrometers are cheap and the "little balls" using the turkey baster type will tell you instantly if you are dealing with a bad battery or not.

If it is a bad battery, my vote is for the AGM type 6-volt golf cart batteries, you'll have to buy two....of course we are prejudiced, we have 6 of them.

[HamRad]

David,

When we bought our batteries in Q there was a sale. Given the nature of Q I'm betting there will still be a rather large selection of batteries! No need to travel into Phoenix.

On your way back to Q I assume you'll simply go north and take the road that comes out at Buckeye. If you haven't taken that road it is a good one and saves a lot of time.

Dennis

[billhoover]

Disconnect the battery from the charger (it should sit for a while, don't recall how long) then check it with a multimeter:

12.6 or more, 100% state of charge
12.4 to 12.6, 75 to 100%
12.2 to 12.4, 50 to 75%
12.0 to 12.2, 25 to 50%
11.8 to 12.0, 0 to 25%
below 11.8, 0%

[rogue]

As Bill said above, just make sure each battery is checked separately and isolated (not connected to anything no connection to the other battery). It may be hard to see the voltage difference on an analog multi/volt meter, but easy if you have a digital one.
Bob

[swanny]

as stated above referring to the weakest link. a not so new battery will have an adverse effect on the new one. and yes tested under load is the way to test. now the reason i say this is my one son works for a company that does "ups" systems (unlimited power supply). he always tries to keep me going on the right path when it comes to the way i treat my batteries. if one of your batteries is on its way out this would be a good time to go with the twin 6's. my son isn't here right now to ask question so i will stop here.