Just a quick one.
I've got three old car batteries sitting in the garage that have died through lack of use. I was wondering, is there anyway such batters can be restored?
Assuming these 3 batteries have sat in your garage unused and not needed is there any point? Do you need them? I'd take them to the scrappy.
It is possible to fix them - but to do it properly is going to cost you a few quid.
The chances are the plates are caked in lead sulphate which is what kills batteries essentially, it is part of the chemical reaction that makes a battery work - basically as you discharge a battery the sulphuric acid in the electrolyte is turning to lead sulphate which coats the plates, as this happens the electrolyte becomes more watery (which is why you can measure a batteries specific gravity to confirm it's health - which is how those little coloured ball indicators work on the top of some and also why a discharged battery in the winter will freeze and kill it). When this happens the plates becomes less conductive as they are plated in lead sulphate and of course the electrolyte becoming weaker means the chemical reaction and the release of ions to the lead which in turns releases electrons is slowed, we see this as a drop in voltage and current capacity.
In normal operation when your alternator kicks in or the battery is charged the extra electrons flowing back in attract the hydrogen ions in the electrolyte and the hydrogen reacts with the lead sulphate which turns back into sulphuric acid - during this normal process the lead sulphate is removed again from the plates and the electrolyte returns to near full strength. With age this reaction does slow and voltage and capacity fall - prime killers are hard discharging and letting them discharge with no prompt recharge. During heavy discharge or long periods of low charge some of the lead sulphate falls off the plates and lands at the bottom of the battery case - this has now been removed from the chemical reaction and will not form up to make sulphuric acid again during the next charge as it will never get the electrons from charging to release the ions. This is a viscous cycle as well, because as the battery ages the chemical reaction weakens and and when discharging it needs to remove more and more from the electrolyte to the point that the electrolyte can get so weak that the battery basically just drops to a voltage so low it's useless - but your still trying to pull power to for example start your car, and the plates cake up fast as all the ions rush to the lead - more fall off and before you know it you have a battery irreparably damaged.
This is why I don't like to start a vehicle move it 2 feet and turn it off, wash it, then do the same again an hour later. Or people who just like starting and stopping engines all the time without sufficient time in-between start cycles to recharge a battery.
So the way to save a battery is to charge it to remove as much lead sulphate as possible, then carefully (you are dealing with acid) drain the batter and flush it upside down with water to remove all the solids from the bottom. Then you can replace with new electrolyte - you can make it with distilled water and sulphuric acid.
Other stages can involve adding other chemicals to help strip the plates but if it needs that frankly the battery is gone.
I have in the past had good success with a battery simply by adding a little sulphuric acid & distilled to each cell.
