Battery charging question

[jnyork]

Bought a used RV, the batteries were both stone dead having set all winter and this summer without charging. Plates were still covered, not exposed. Put my little 8-amp charger on one of them just to see, it has now been charging about 18 hours, bubbling merrily away, still taking 4 amp charge.

Is this battery shot or do I keep charging until the rate comes down to 2 amp?

I know, this does not sound like a leverguns question, but be assured this RV will have some leverguns in it as soon as I get it ready go go.

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[williamranks]

Give them a couple more days then take them to the local auto parts and have them do a capacity test.
If one of them is for the engine have the capacity test done twice, had a battery once that only had enough storage capacity left for one start.
Had to drive 30-40 miles before I could shut the engine off and get a restart.

[horsesoldier03]

Does your charger have a gage that shows when the battery is fully charged? If so, where does it register. IMO, try to crank it and if it cranks and your alternator is still pushing the right amount of voltage, technically you should be good, the question is, for how long?

Being that it is a vehicle new to you, you have no idea when the batteries were installed unless the date tags are still there. Good batteries should last about 5 years. When I buy a used vehicle, the first thing I start doing is performing routine maintenance to ensure I wont be on the side of the road stranded. Check the fluid and filters, and in this situation, I would put new batteries on it, and then pull all the hubs and check bearings and repack and then check brake pads and rotors for wear. If you let those go bad, your going to spend a lot more than if you replace them before they fail.

[7.62 Precision]

Were they dead in freezing temperatures?

If so, they may "charge" forever without ever really holding a charge.

At any rate, let them charge for a bit, check voltage, and then let them sit for a few days (unhooked) and check again. As long as you have time to play with them, of course.

Sometimes they will charge and can be used and recharged, but after a bit of time the charge is lost, so you can think you have a working battery, but after a couple weeks, you won't be able to start.

[jnyork]

The batteries were in an RV, not a vehicle, and yes exposed to freezing. They are dated 2006 so I didn't expect much out of them, just thought I would give it a try. Will trade them in forthwith, not worth messing with any longer. Thanks for your replies.

[jcw]

18 hrs. is a long time. Take them in for a load and capacity test. I see new batteries in your future.

[wm]

2006? Dead for months? I wouldn't trust them. Liable to let you down at the worst time.

[mikld]

I would push as much amperage as I could into the batteries. Charge @20A for a couple hours, drop to 10-15A for a few hours and do a load test. 8 amps ain't much more than a trickle. Are the deep cycle? Standard starting batteries? Makes a difference...

[Hagler]

jnyork,

If you have one of the newer "smart" battery chargers, then you may want to try using an oldtime "stupid" charger. The microprocessor-controlled battery chargers do not treat batteries the same way that the old ones do. Advancement is not always moving ahead.

Shawn

[Hawkeye2]

What Hagler said is right on. Just short of 40 years my Big A charger turned belly up and I had to buy one of those intelligent chargers. What it won't do: Sense a completely dead battery and begin a charge, you have to hook another battery in parallel with the dead one to get it to recognize the load and begin a charge. This feature also makes it absolutely useless for bench testing starters and generators (remember those?) or powering up any 12 volt item. It won't start at a high rate so you can "shock" a dead battery to begin a charge. They tell me that these features will protect the battery and insure a long life but I never had any trouble exceeding the manufacturers advertised life span specially with the pre maintenance-free ones and I lived in a climate that was hard on batteries for quite a bit of my life.

Always keep a battery clean, specially one that only sees intermittent use. The accumulation of dirt, dried electrolyte and so on that builds up on a battery is conductive. The battery will self discharge between its own posts and to the holddown. I always sit the battery on a rubber sheet (old inner tube) and place pieces of the same between the battery case and the holddown. Try this : Take your multimeter and set it on a range of about 20 volts. Place the + lead on the battery's + post and drag the - lead of the meter across the top of the battery. Don't be surprised if you get a reading. Two or 3 volts isn't unusual and won't hurt much in a car that is used every few days but it will drain a battery that is left without getting a charge every few weeks. The voltage reading you get from the "nonconductive" battery case is current flowing from one post to the other. I have seen readings as high as 10 volts on the batteries in electric powered manlifts and a crew wondering why they won't hold a charge.

BTW, your batteries are fit only for scrap. Don't burn up a charger trying to revive them.

[Chuck 100 yd]

If they are not DEEP CYCLE batteries, they are TOAST. Quit wasting your time.
Even if they do come back to some extent they wont last long.