Battery boiling while charging; YIKES

[beppington]

I have a one-year old Walmart 12V deep cycle battery I just charged overnight with a Sears DieHard charger I've had for over a decade. I've never felt real knowledgable about battery charging; Just connect it up overnight & hope for the best. I did read the manual but never used the charger often enough to feel like I really knew what to expect/ whether I was really doing it right.

This time the deep cycle battery started boiling

The charger has three switches:

- 6V / 12V
- "Automatic Regular" / "Automatic Deep Cycle" / "Manual"
- 2 AMP / 10 AMP / Engine Start (which is 60 amps)

Per the charger's book, I set it on 12V, Automatic Deep Cycle, & 10 AMP. And the battery boiled. When I checked the battery this morning after charging overnight, the meter display, instead of showing its green "Full Charge" light with the needle pointing to 100% charge, it showed maybe 75% charge & of course the battery was boiling.

Is it normal/ OK for a battery to boil while charging? Did I do something wrong? Could the battery already be a dud?

This is a marine deep cycle battery that was used only 2 or 3 times last year, then sat until last weekend when I charged it just for a few hours (no boiling). I figured that was good enough for then, then went to do a good, full charge last night.

Thank you ...

 

[hawkeye08]

Is the battery hot to the touch? I suspect that the 'boiling' you are seeing is just the off gassing when a battery charges. Automatic chargers can usually do a decent job of charging properly. Make sure to use distilled water if you need to add some.

BTW, one of the checks for a bad battery is with the caps off watch for bubbles in each cell. Often a bad battery will have one or more cells that do not bubble when charging.. usually means a dead cell, resulting in bad battery.

Always think safety, wear eye protection when messing around with batteries.

Good luck!

 

[tallyho8]

Set on 10 amps the charger should have had the battery fully charged in a few hours.

It is one of two things.

1. The battery is bad. Check it with a voltmeter. If it is below 12 volts it is bad and the charger will never shut off.

2. If the battery has 13+ volts and the charger is still running then the charger is bad.

I always charge a battery overnight on 2 amps. If you are in a big hurry, use 10 amps.

 

[wrenchturner]

The battery is not really boiling. The bubbles are hydrogen and oxygen gasses coming from the H2O as the current passes through it. The reason a shorted cell does not bubble is because the positive and negative plates are touching thus no current travels through the electrolyte.

As a battery becomes closer to being fully charged, more and more bubbles come from the electrolyte. This is when the battery is more likely to explode. Ever heard of spontaneous combustion? These gas bubbles like to stay attached to the surface of the battery plates much like bubbles like to cling to the side of a bottle when shaken. This causes a problem because even hours after you have taken the charger off, it only takes a couple of the hydrogen and oxygen bubbles to get together to begin the combustion process. If you are ever looking at a battery closely when it explodes, you had better look closely because you will never see it happen again. Why? You are going to be blind. I have seen one explode from a distance. It really shook the building.

A fully charged battery will be 12.6 volts. However, if you check the voltage of a battery right after it is removed from a charger they all will read a little over 13 volts. If you place a meter on the battery at this time it, you can watch the voltage slowly come back down to 12.6 volts. I think the previous post was refering to a 3 minute charge test. In that case if the voltage is higher than 15 volts after charging at a high rate, then the plates a sulfated.

 

[77transam]

First I'd make sure the battery is good. 2 sure-fire signs it's not:

1)If the sides are bulged out and hard (you can't push in on them because the plates have expanded. Lots of batteries have sides bulged out but you can usually push them in by hand.

2)f the positive terminal has 'raised' (the top of the battery is no longer flat near the positive terminal, it actually sits up a bit higher than the negative one. Sometimes you'll even see stress marks or cracks in the plastic around the pos. terminal.

Also make sure the water level is not too high/low. (should be no more than a 1/4 to 1/2 inch above the plates.) If it's low, use distilled water. Check level before and after charging.

Sometimes though a good battery can sit around dead for a while and it gets sulfated and boils at pretty low voltage. If you keep charge on it for a long time the voltage at which it 'boils' may rise and the battery might come back to life. 12.3 volts is below full charge -Put a good load on it and see how much capacity it has.

And just like Norm Abrahm says, ALWAYS wear safety glasses when working in the shop. (Especially around batteries/sulfates!) Latex gloves ain't a bad idea either.

 

[tallyho8]

I have the same charger the OP has and I can charge a fully dead battery on it overnight on the 2 amp setting and in the morning it will read "fully charged".

If I set it on the 10 amp setting the battery will read "fully charged" in about 4 hours or less.

If he had the charger on 10 amps all night and it wasn't reading "fully charged" in the morning, either the charger or battery is bad, probably the battery, because if it doesn't reach a certain voltage, then the charger won't read "fully charged" and cut off.

Naturally, the battery should be full of water before charging but if it wasn't, then all the cells wouldn't be "boiling".

 

[beppington]

Is the battery hot to the touch?

Very, very warm but not gonna burn your hand.

Make sure to use distilled water if you need to add some.

I forgot to mention in my OP that the water level is perfect-O.

BTW, one of the checks for a bad battery is with the caps off watch for bubbles in each cell. Often a bad battery will have one or more cells that do not bubble when charging.. usually means a dead cell, resulting in bad battery.

This I didn't do, but can. Maybe I'll stick the charger back on it tomorrow & check it that way.[/QUOTE]

 

[beppington]

Set on 10 amps the charger should have had the battery fully charged in a few hours.

I didn't know it'd be that fast.

Check it with a voltmeter. If it is below 12 volts it is bad and the charger will never shut off.

Just checked it: 12.85 volts

I always charge a battery overnight on 2 amps. If you are in a big hurry, use 10 amps.

OK, I'll do that from now on. Again, just didn't realize how quick it would charge. I've always just "set it & forget it"

 

[beppington]

If the sides are bulged out and hard (you can't push in on them because the plates have expanded. Lots of batteries have sides bulged out but you can usually push them in by hand.

The sides are not bulged out at all, but I'll have to run out & check for softness.

2)f the positive terminal has 'raised' (the top of the battery is no longer flat near the positive terminal, it actually sits up a bit higher than the negative one. Sometimes you'll even see stress marks or cracks in the plastic around the pos. terminal.

Not this either. The battery's physical shape & appearance look great. It's practically brand new.

Also make sure the water level is not too high/low. (should be no more than a 1/4 to 1/2 inch above the plates.) If it's low, use distilled water. Check level before and after charging.

Again, the water level is perfect.

Put a good load on it and see how much capacity it has.

Will check it tomorrow.[/QUOTE]

 

[gdh]

Why only distilled water?