how to restore a lead acid battery

[woolleymoor1]

its a large one and replacement is too expensive

[HowardKennitby]

It might help if you could tell us what is wrong with it.

[woolleymoor1]

sometimes OK and others no voltage

[woolleymoor1]

been told to drain wash out posible debris and replace acid. i.e.start again

[scotman]

Are you sure this a viable exercise?
It seems that the time and expense will both be large. You may not get all the debris out and if the plates are disintegrating and shorting out on one another you are unlikely to get the battery fully operational again.
You have supply, disposal, and safety problems to resolve with no guarantee of success.

[woolleymoor1]

Many thanks, sounds like a new battery ,its off a verylarge mowing machine

[scotman]

One possible short-term fix.
Do you have access to the individual cell connections and a voltage meter. It may be that only one cell has died and this could be shorted out. Obviously this reduces the output voltage of the battery but could extend its life while you save up for a new one.
I have done this with a rechargeable drill and it does work short-term.

[beso]

I used to work in the solar industry. There are no magic fixes. Fooling around with cleaning them out is unlikely to do any good.

Yes they can be shorted by sludge at the bottom. However they are more often shorted due to swollen plates puncturing separators or bridging at the edges.

Moreover the sludge is active material that has fallen from the plates. If you add sulphuric acid at the concentration of a new battery the grids will be consumed in the discharge reaction so the "restoration" will be very short.

[AlBags]

Once they're gone .. they're gone.
Dead cells = New battery ... Sorry.

[AlBags]

Go to a truck salvage yard and buy a couple. Ask them to test first on a truck engine.

[DTCwordfan]

Oh let him do it and then we can read about the moron who poisoned/burnt himself to death in the Daily Mail - oh well AOG can for us.

[Clanad]

At least try this before deep sixing the battery... Clean the posts (where the battery attaches) thoroughly. Use common baking soda mixed about 1/2 cup to a cup of water (warm water works best) and pour slowly over both terminals (after removing cables). Be sure to wear safety goggles (or other eye protection) and some gloves... don't get any residue on your clothes either, unless you're wearing all wool). Using an old tooth bursh clean the posts and the terminals (just dip the termnals into a plastic glass filled with the soda mixture and rinse). Place a light layer of common petroleum jelly on each terminal and reassemble. If this helps, then tape two copper coins (here in the U.S. they're pennies) to the top of the battery... any new corrosion will attach to the pennies rather than the freshly cleaned terminals...

(Alternately, Seven-Up or other similar citrus based soft drink will clean the terminals and cables as well)