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I have a car battery that I am trying to recharge. It measures 3.28v, and my charger is a Selmar Turbo 8.

This is the charger I am using:

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Here is a picture of the ammeter gauge that I found

enter image description here

First of all I tried to charge the battery overnight and the current was about 0A. I left it overnight and came back the next afternoon, and the battery was hot to the touch, and the charger was cycling on and off, with the current about 4A.

I turned off the charger and the battery was making a quiet hissing noise, like water in a pipe, and it made this noise for about 10 minutes, so I levered off a cover and there were some holes. The voltage was about 6v at this point.

These holes were completely empty, and the battery had a strong smell, like sulfuric acid with these holes open. The battery must have been empty as it did not slosh about at all when I moved it. I filled the battery with deionised water and tried to charge it again after leaving it to cool.

I left it to charge for 3 hours, and the voltage is back down to 3v.

The charger goes up to about 12A on the ammeter gauge, which is the maximum, and then trips if I try to charge the battery on the High or Low setting at 12v, and High at 6v.

The current at 6V on the low setting is about 6A.

Have I completely destroyed the battery? Should I just buy a new one?

I don't know anything about the battery, the label is filthy, but it's a 12V car battery and its sat for about 8 months.

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    You should recycle dead car batteries - the local scrap merchant will take it and pay a couple of dollars. The lead is the useful and recyclable part, plus it keeps the lead and acid out of the local garbage stream.
    – Criggie
    Jun 13, 2016 at 1:44
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    At 3.28v, wasn't it already probably destroyed?
    – user253751
    Jun 13, 2016 at 4:12
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    Agreed, if a 12V battery was at 3V already it's basically a large paperweight.
    – I have no idea what I'm doing
    Jun 13, 2016 at 7:01
  • The per cell nominal voltage of a lead acid battery is 1.95 (fully discharged) to 2.10 (fully charged) volts. Yours is almost certainly around 0.55 volts.
    – user
    Jun 13, 2016 at 11:58

3 Answers 3

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The battery is toast. Save yourself potential serious injury. Buy a new one. If the battery has been dead for eight months...it is pretty much a goner.

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    Spot on advice. The "sulfuric acid" smell is none other than sulfuric acid, with a lot of potentially flammable hydrogen too. None of these things should ever be attempted indoors. And never attempt to charge a 12V battery on 6V, that will actually drain the battery, and potentially destroy the charger or both. A 12V battery is actually a series of smaller batteries added together to yield 12V. You might notice a 12V serviceable battery has 6 "holes", where a 6V battery only has 3.
    – SteveRacer
    Jun 12, 2016 at 22:40
  • @SteveRacer: Most definitely...
    – Old_Fossil
    Jun 12, 2016 at 22:49
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    +1 and seconded. A car battery's charging process DOES produce real acid and explosive gas. It is really dangerous. Maybe you think it is a "Caution, coffee is hot" kind of label, but it is much worse than that. You can kill yourself by charging a car battery indoors.
    – Nelson
    Jun 12, 2016 at 23:47
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    Just to add to @SteveRacer on the point of not charging batteries indoors - I have the habit of taking batteries out of the vehicle too, before charging with an external pack. Sit the battery on a piece of wood or a mat when charging, as a cold cement floor can do [some kind of magic which I can't explain] and drain the battery. But I've had two separate occasions of cars catching alight with a charger plugged in, so I've taken to the 'better safe than sorry' approach and keep a charging battery well away from everything else.
    – Aaron Lavers
    Jun 13, 2016 at 9:02
  • @Aaron Sorry, I do not share your magic floor fairy depletion mythology. I have done this experiment more than once, under controlled conditions, to win bets. And I've always won. The only thing I'd say about batteries on the shop floor is that they get dusty and filthy, which might form a small high-resistance depletion path between the posts. But no alien concrete electron induction worms. None.
    – SteveRacer
    Jun 13, 2016 at 15:33
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The "strong smell, like sulfuric acid" is in fact sulfuric acid, which is the acid component in a lead-acid battery. If it's coming out strongly enough for you to smell, the battery is dangerous. Recycle it and get a new one!

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If there truly is no liquid in it, you cannot charge it. Attempting to will have no effect. But if there is some, and you try to charge too fast, heat and explosion hazards are produced.

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