lead acid battery

Can You Rejuvenate A Lead Acid Battery? 3 Trusted Methods

Do you have a few old lead-acid batteries in your garage that have been laying around for months or years because they won’t hold a charge anymore? Before you throw them away, you should try rejuvenating them. Although not every battery can be saved, so you may find yourself asking, Can I rejuvenate my lead acid battery?

You can rejuvenate a worn out lead acid battery by removing sulfate build ups with multiple methods. Those methods include the use of a trickle charger, electronic desulfator, chemical desulfator, or a homemade epsom salt mixture. Rejuvenation can last for years, but is not infinitely repeatable.

In this article, you’ll learn the most common reason that lead-acid batteries stop working, how to identify bad cells in your battery, along with a few methods to rejuvenate your battery and safety precautions you should take to do so. Let’s get started.

Plus more info later in the article on a Lead Acid battery rejuvenation PDF download from someone utilizing his own techniques for off the grid living!

What Are Lead Acid Batteries, And Why Do They Stop Working?

lead acid battery

Lead acid batteries are by far the most common type of battery. They’re used in everything from cars and trucks to golf carts. Over time, these batteries can experience something called sulfation. Sulfation is when lead sulfate crystals build up on the surface of batteries lead plates and accumulate in their pores.

All lead-acid batteries are at risk of sulfation, which causes their inner battery plates to degrade over time, and become less conductive. Sulfation is the most common reason for a lead acid battery to lose a majority of its charge.   

Just because your battery is down doesn’t mean it’s out completely! You can desulfate your lead-acid battery and rejuvenate it fairly easily. This can add years to the lifetime of your battery, and save you hundreds of dollars.

All lead-acid batteries use essentially the same principles. This means you can use the same methods to rejuvenate all lead acid batteries. Although if you have a maintenance-free or sealed lead acid battery, they will have hidden caps that will need to be removed before you can revive them.

So to rejuvenate your battery, you need to remove the sulfation build up on the cell plates! Although a good first step to treating any battery is to use a wire brush on the terminals and make sure they are very clean. This will make the battery conduct better, and reduce possible damage.

Safety Precautions

Working with lead acid batteries can be hazardous. As the name suggests, they’re filled with both lead and a corrosive acid. Neither of which you want to get on yourself.

For this reason, you want to always wear safety goggles and gloves when handling lead-acid batteries.

The plates and electric cells in your battery should also be undamaged and functional. Some lead sulfate buildup is normal and the problem we are trying to fix. But if your battery is damaged in any way, it’s unlikely that your battery can ever be rejuvenated and working on it may pose a safety threat.

If you plan to follow one of the methods that requires you to remove and discard battery acid, make sure you have a container that can handle it. Then make sure you take it to the appropriate center to dispose of it.

General Items You Will Need

Treating Bad Cells Vs All Cells

Before you decide which method you want to use to desulfate your batteries, you need to decide if you are going to treat all of the cells or only the bad ones. Not every method requires you to make this decision but some of them do. 

If you do not consider yourself electrically savvy, it may not be a bad idea to play it safe and treat all of the cells. If you know what you are doing, only treating the bad cells will increase the overall lifespan of the battery.

lead acid battery

Identifying Bad Cells

First, you’ll need to fully charge your batteries for at least 12 hours. Then disconnect your batteries from their chargers and let them sit for at least 10 to 15 minutes to rest before you begin working on them.

Start by opening up all of the battery caps. If you’ve got a sealed lead acid battery, you’ll need to do a Google search to find out how to open your caps. Next, fill each section up to the suggested water levels. 

This is really important, because later on in this process there could be sparks created in each compartment. The empty section of each column is filled with air which contains oxygen and hydrogen. These elements have a risk of exploding and sending acid flying everywhere. 

Higher water levels mean less room for these air to build up, and less risk of the battery exploding in your face. Use a flashlight to make sure you’ve got the water level correct.

Measuring Voltages

Now, measure the terminal voltage of your battery to make sure it’s fully charged. For a 12 volt battery, it should be in the range of 11.8 volts to 13 volts. Anything lower than 11.8 volts indicates that you likely have a cell imbalance from one of the cells not working correctly. 

If your battery measures below 10 volts, it is too damaged to be repaired and should be replaced. If your battery measures between 10 and 11.8 volts it can be rejuvenated

Assuming you have some issue with your lead-acid battery, you’ll next want to measure the voltage of every cell to find out which one is causing the problem. Put one end of a multimeter probe into the cell solution and attach the other to one of the terminals.

Your cell should have a voltage equal to 1/6th of the total battery voltage, assuming you have a typical 6-cell battery. For a 12 volt battery, that means you should get a reading of at least 2 volts from each cell.

You’ll also likely be able to visually identify which cells are a problem because they will have different color plates from normal cells. This color difference is because of a buildup of lead sulfate crystals, which aren’t conductive.

Rejuvenation Method 1 – Trickle Charging

Use a trickle charger.  If you attach a battery trickle charger to your lead-acid battery, it will slowly dissolve sulfation. This method is extremely slow and you’ll probably need to let your battery continuously charge for a week or more. But eventually, it will remove the sulfation and revive your battery so that it can hold a charge again. 

There are also computerized smart chargers that can be programmed to do this. They are usually referred to as a  specialized desulfation device. These work by sending pulses of charge to the battery instead of a slow constant charge, although you still need to leave it connected for a handful of days. They can sometimes work better than a trickle charger.

Rejuvenation Method 2 – Chemical Desulfators

You can buy specialized chemicals called desulfators to dissolve sulfate build up on your lead battery plates as well. This is where you will need to decide if you want to treat all cells or just the bad ones. It is as simple as pouring it into the filling ports of your battery, but make sure you try the tickle charger first. For the correct reaction to occur, the battery needs to have a charge. Common chemical additives include magnesium sulfate, caustic soda, and EDTA.

These chemical additives are very reliable and nearly always show an improvement. Plus the additive itself is nontoxic and has an infinite shelf life. 

Photo: Amazon

Rejuvenation Method 3 – Epsom Salt Solution

This method is the least likely to work, so I recommend trying the other two methods first. This method also requires you to be a lot more careful. You may have to remove battery acid, which is an extremely strong acid and something you do not want to get on you. Also make sure to put it in a glass container, because it will eat through most plastics over time.

For this method you are going to need a few extra things that were not listed on the general list.

Start by boiling a small amount of distilled water(about 12 ounces) and slowly mixing in the epsom salt. This is like dissolving sugar in your sweet tea. The heat will make more of it dissolve, and you want to keep stirring and heating until no more epsom salt will dissolve. It may also be a good idea to do this after you figure out how to take the caps off of the battery cells.

Once you have your battery cells open and your epsom salt mixture created, use the syringe to remove the battery acid in each cell(or only the bad cells) until they are about 50% full. Then go back and refill the cells with your epsom salt and water mixture.

Before you seal your battery back up, you are going to want to hook it up to the trickle charger for a while. This process could release some gasses while it desulfates the battery plates, so make sure to leave the battery cells open. Also make sure you place the battery out of reach of children while it is desulfating. 

Photo: KDE

Refilling Battery Cells

Run the trickle charger for a few days to properly desulfate the battery plates. Then you need to discharge the battery and remove the epsom salt-battery acid mixture. Do not skip over the discharging step. You then want to fill the cells with new acid that is diluted to 35% acid, and 65% distilled water. Battery acid is just diluted sulfuric acid, which is much cheaper than a whole new battery.

Lastly, reseal your battery cells and recharge your battery. Your rejuvenated battery should last nearly a year longer. This process can be repeated 3 to 5 times before it is no longer effective.

Additional Tips

  • If you aren’t using a lead acid battery regularly, remember to at least charge it every 3 months to prevent too much sulfate buildup. Don’t store lead-acid batteries in a discharged state, as this will shorten the battery life.
  • Always do battery troubleshooting and repairs in a well-ventilated area.
  • Using a syringe can make it much easier to add water into the cells of your lead-acid battery.
  • Make sure to use a charger that provides the right amount of voltage for your battery. Different types of lead-acid batteries require a different charge voltage. Don’t try to increase the voltage to speed up charging time. You can overcharge your battery, which causes excessive heat and can kill it within a matter of hours.
  • Store your lead-acid battery in a cool and dry place. The ideal temperature to store your lead-acid batteries at is 68 degrees F. Significantly higher or lower temperatures can shorten your battery life.
lead acid battery

What causes sulfation in lead-acid batteries? 

Lead acid batteries are a type of wet cell battery. Every cell contains two different lead plates in a fluid containing sulfuric acid, called an electrolyte. If the electrolyte level in your battery gets too low, the lead plates are exposed to air and sulfation can occur. Sulfation is a buildup of lead sulfate on the electrodes of the battery, which stops electrons from flowing between plates and prevents your battery from retaining a charge.

Can I use vinegar to rejuvenate my lead-acid battery?

Adding vinegar to a lead acid battery isn’t recommended. Vinegar contains acetic acid, which can react with both the lead terminals and sulfuric acid in your battery to create lead acetate. You can use small amounts of vinegar to clean the outside electrodes of a lead-acid battery though. To do this, mix a small amount of vinegar with baking soda to create a paste and use this to clean the external electrodes on your battery.


For more information and special tips & tricks on the car, battery rejuvenation check out this battery reconditioning guide by Mike who has been living off the grid in Michigan and rejuvenating his own batteries for years.

Have you ever used any of these techniques, or have any tips of your own? Let us know about them in the comments section below.

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