What to do with overfilled battery?

[zmoz]

I have a battery (lead acid starting) which hasn't been used, but is a couple years old. It spent a little while out in the rain, and some water seeped into a few of the cells. Now when I charge it @ 1 amp it overflows.

What should I do? Should I just let it charge and overflow until it stops? Should I suck some of the acid out of the overfilled cells with an eye dropper? Or do I need to completely replace the acid in all the cells now? (probably throw out the battery instead)

[Clifford]

Could try a turkey Baster.

What are those battery testers that use specific gravity? (hydrometer) Should be available at auto parts stores.

Actually, get one of those specific gravity battery testers (hydrometers).  Suck out some fluid and see what you get.  I haven't used one, but most of the cells should read the same.  Don't put all the fluid back into the cells that you are wanting to drain down a bit.  Put the excess in a glass jar when you are doing your testing.

I think purchasing new battery acid at and auto parts store is relatively cheap.

[Nando]

ONLY ONE SOLUTION

Empty all the electrolyte and buy new Electrolyte from a battery store, now -- do not try to charge the battery

Nando

[rottingspinalcord]

doesnt sulphuric acid like burn the hell out of glass? one thing to do with dead batteries is to crush up asprin and put it in the cells, i dont know how this affects the rechargability of the battery but it sure as hell makes it put out electricity, i did it once when my uncles car was DEAD in the middle of nowhere on the way to florida.

[johnlm]

I believe it is hydrofluoric acid that eats glass.  Sulfuric acid does not affect glass.

John

[dinges]

If the battery would have just been overfilled with distilled water, I'd simply let it sit open for a while (a long while, I'm afraid...) for the excess water to evaporate. You might speed it up a little by heating (say 30 C?), but I personally wouldn't do this.

However, you have rainwater in your battery now. Don't know how pure that is compared to distilled water, but it may have some salts in it that may interfere with the battery. You could still try to let it evaporate and see if it works, but perhaps electrolyte change is the only good way to go... (I have no experience exchanging electrolyte, BTW).

Sulfuric acid doesn't damage glass; in fact, WWII batteries of german subs were partly made of glass. It's HFl (hydrofluoride-acid) that attacks glass (is used for etching glass amongst other things. The stuff is almost impossible to find (in small quantities) over here...)

Good luck,

Peter,

The Netherlands.

[wooferhound]

aspirin does not work

http://www.fieldlines.com/story/2003/9/2/20374/57860

[whatsnext]

Sorry Nando but this is bad advice. Letting the two overfilled cells evaporate off and then correcting the specific gravity in them after the battery is charged is a better idea. There is surely disolved sulfates stuck to the plates of this battery because it's unlikely to be fully charged. Draining the weakened electrolyte and putting in fresh electrolyte will likely destoy the battery. In theory you could partially drain the two cells, charge the battery, and then adjust the SpGr but the first idea would be easier. The battery should not outgas much at 1A so it's probably completely sulfated and the original poster is hosed. Thankfully starting batteries are pretty cheap.

John...

[RC in FL]

If they have not been used for couple of years and not kept charged they are likely bad from sulfide crystal formation.

As to changing electrolyte, fully charge the battery before evalating or changing the electrolyte.

Discharge converts lead + sulfuric acid into lead-sulfate and water, charging reverses this.  Charging is complete when you converter all the lead-sufate back to lead and restore the concentration of sulfuric acid (normally about 35% at full charge)  The recharging process needs to happen within a few weeks to maximum of about 6 weeks or the fuzzy soft lead-sulfate crystalizes on the plates.  Once it crystalizes it is locked up and will not reconvert during recharge.

As to hydrometers they are selling in most auto parts stores, if they are half moon shaped with little black plastic pointer, don't waste your money. Get a good tube-float design, about $20 to $25.

% State Of Charge    Specific Gravity Corrected 77 F    Open Circuit 12-Volt

100.     1.277    12.72
     
90.     1.258    12.60
    
80.     1.238    12.48
    
75.     1.227    12.42
    
70.     1.217    12.36
    
60.     1.195    12.24
    
50.     1.172    12.12
    
40.     1.148    12.00
    
30.     1.124    11.88
    
25.     1.111    11.76
    
20.     1.098    11.70
    
10.     1.073    11.58
    
0.     1.048    11.46