Lead acid batteries often die due to an accumulation of lead sulphate crystals on the plates inside the battery, fortunately, you can recondition your battery at home using inexpensive ingredients.
A battery is effectively a small chemical plant which stores energy in its plates. They are chemically charged with an electrolyte which is a mixture of distilled water and sulphuric acid. When the battery is discharged, the lead active material on the positive plates reacts with the sulphuric acid and produces lead sulphate. When the battery is charged, this process is reversed and the lead sulphate crystals react to form sulphuric acid again. The battery fails when there is an excess build up of lead sulphate crystals which then do not allow sulphuric acid to make contact with sections of the plate. These crystals harden and eventually cause a chemical imbalance in the electrolyte.
In most cases, hardened crystals can be removed using a solution of magnesium sulphate. This method doesn’t restore a battery back to original condition but it will restore it to around 70-80% of its original capacity and can be repeated, allowing you to get a few more years of use out of your battery without having to replace it.
What You Will Need To Recondition Your Battery
- The Damaged Battery
- 400ml (12oz) Distilled Water – Buy Here
- 200g (7oz) Epsom Salts (magnesium sulphate) – Buy Here
- A Syringe or Dropper – Buy Here
- A Battery Charger – Buy Here
How To Recondition Your Battery
Take the battery out of the vehicle, motorbike or scooter and put it onto a solid work bench.
Some battery’s cells are clearly visible on top of the battery and are sealed with screw in caps. Others, like mine, are protected by a “sealing” strip. You may need to cut the edges of this strip to get it loose but it is almost always removable. Look for the edge of this strip and try to pry it up using a flat screw driver, if it is glued into place, try to cut around the edges of the strip using a sharp craft knife.
Once this has been removed, you will also need to take the caps off each of the individual cells in order to get to the battery acid. Some batteries have small rubber caps like these, others (typically on larger batteries) have screw in plugs which can be removed with a large screwdriver, they’re not usually very tight.
Using a syringe or dropper, carefully drain each cell one by one until they are all around 50-60% full, if some cells are already lower than this then exchange some acid from the fuller cells. You don’t want to take too much out as you will then struggle to charge the battery again. The liquid you are removing is a strong acid so put it into a glass container and be careful not to mess any of it on your hands or clothing.
Make sure that you dispose of the removed battery acid in a safe and responsible manner. The removed battery acid is extremely corrosive and contains heavy metals, mainly lead.
Now you need to make a saturated solution of Epsom salts (magnesium sulphate) and distilled water. Do this by boiling water and continuously stirring in more salts until no more will dissolve in the water. Then fill each cell with the Epsom salt solution to the full level line using the syringe or dropper.
When charging the battery while it is being reconditioned, some gas will be released, so it is advisable to leave the caps open. Connect a battery charger to the terminals and let it complete the charging cycle. If the battery is heavily drained or damaged, it may have to be charged overnight with a trickle charger at a very low amperage. If you do not have a battery charger then replace the battery cell caps and covers and reinstall the battery in the vehicle. Jump start it and then take it for a full hour or two drive to allow the battery to charge using the alternator.
The reconditioned battery should now last another 6 months to a year and can usually be restored using this method about three to five times until it is no longer effective.
Edit: As some users in the comments section have suggested, the best solution would be to let the reconditioning process run for a few days to properly “clean” the plates and then drain the Epsom salt solution from the battery and replace it with the recommended 35/65 acid solution. Make sure that your battery is discharged before removing the Epsom salt solution and replacing it with the acid solution.
Have you tried to recondition a battery using this method or a similar method? Let us know in the comments section below.
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Hi, my name is Michael and I started this blog in 2016 to share my DIY journey with you. I love fixing, renovating and building – I’m always looking for new projects and exciting DIY ideas. If you do too, grab a cup of coffee and settle in, I’m happy to have you here.