I have restored old batteries with this simple method.
The only required materials are a dead battery, distilled water and a homemade battery charger.
This process should restore any dead lead acid type due to old age or use. First of all, inspect the for any physical defects like Burnt connectors, melted plastic housing, warped battery sides or visibly warped or badly damaged plates inside are signs of damage.
These defects are signals that a battery can’t restored.
If no visible signs of damage are present, then most likely it can be restored using this method.
First, wash the battery thoroughly with lots of water and baking soda. A soft brush is useful for any oil or dirt stuck on the body. Dish soap can also be used to clean very dirty batteries. The baking soda reacts with the battery acid, rendering it harmless.
Next, carefully pry off the cell covers with a screwdriver. Wear old clothing or an apron to protect your clothes from battery acid. Acid will quickly eat through clothing.
Set the covers aside. Now you may want to use a Shop Vacuum machine to clean out any larger dirt particles. Be careful not to let any dirt fall into the cells. Take a damp paper towel and clean the area around the cell holes.
Fill the cells to just above the plates with distilled water. Do not use anything except for distilled water. Tap water has minerals that will corrode your battery. Some have a plastic cover over the plates. Fill to just above the top of the plastic cover. It is easier to use a smaller bottle to avoid messes when pouring.
Pour slowly to prevent over filling. The battery is now ready for charging. A very old and used battery can take over 20 ounces of distilled water!.
Now is time to charge back. Conventional battery chargers will most likely not be able to charge or you would not be on this article in the first place. The special pulsed radiant energy used in the Charger breaks up the sulfation on the battery plates and restore the battery to full power.
It may take multiple cycles on the charger to restore a very old battery. Often, as it nears its top charge level, you may want to slowly discharge and recharge it on the Charger again. With each cycle the battery will gain usable energy until it is fully charged. An auto light bulb and some wires are useful to slowly discharge. Be careful and watch the voltage while doing this. Do not discharge the battery below 11.5 volts so as not to cause any harm to the part. Recharge and repeat as needed until the battery is fully topped off. A fully charge will sit between 13.5 volts to 14.5 volts when finished.
Be very careful when working with batteries. Never work on a lead acid battery indoors. Always work in a well ventilated area. Batteries release explosive gases when being charged. Be careful working around battery acid. It is very corrosive and will burn skin, clothes and tools. Be sure to wash hands and tools thoroughly after working with lead acid batteries.