How To Desulfate A Lead Acid Battery?

While we are developing more efficient methods to contain electrical energy, a few are still popular with several applications. We might see solid-state batteries in regular use 20 years from now, but lead-acid batteries dominate the market. Recent statistics show that the global market for lead acid batteries shall exceed USD 44 billion by 2028, with an average CAGR of 4.4%.

However, they only have a rated lifespan of a few years, and disposing of them can harm the environment. Thus, it helps to make the most of each variant. Whether you use FLA or AGM batteries, sulfation is a significant issue that reduces the battery’s capacity and life span. Tiny sulfate deposits on the electrodes can be challenging to spot but can result in your battery going dead after a few cycles if left unchecked.

In light of that, you may require a few practical procedures to prevent your battery from dying out too quickly. This guide will tell you all about how to desulfate a lead-acid battery.

How to Desulfate a Lead Acid Battery?

There are two methods that allow you to desulfate a lead acid battery. One involves a specialized battery charger/maintainer, while the other involves modifying the electrolyte. For the sake of completion, we’ll be looking at both.

Using a Desulfator

A battery desulfator allows you to remove sulfate deposits without dealing with the more complicated parts of the battery. It’s safer, and you can utilize it through a dedicated mode on a few specialized battery chargers/maintainers. Although, you should keep in mind that it’s much slower. Here’s how it works.

  1. Remove the battery from its circuit and check the voltage with a multimeter. The desulfator can compensate for the voltage, but a lower voltage can decrease the time required.
  2. Expose both terminals and connect them to the desulfator. Check the resistance, CCA, voltage, and any other parameters for your reference.
  3. Turn on the desulfation mode on the device. You require a higher voltage at a shallow current. In the case of a 12V battery, you need to activate the 16V desulfation mode that supplies no more than 1500 mA.
  4. Leave the setup on and check in after every 3 hours. It may take anywhere from 6 hours to a week to complete depending on the sulfation rate.
  5. Once the charger notifies you, turn it off and remove the leads from the terminals. Ensure that the battery is ready to go by using a multimeter.

See full this video: How to Desulfate a Lead Acid Battery

Using Epsom Salts

If you don’t mind handling a few electrical parts, you can use Epsom salts to desulfate a lead-acid battery. It’s a swift method that can get your battery ready for use in a matter of hours. The salts dissolve the sulfate into a water solution for convenient disposal. You can do it through the following method.

  1. Use a multimeter to check the voltage. It must be at less than 50% of its rated capacity.
  2. Disconnect the battery from its circuit and remove the cell covers.
  3. Loosen the terminals and drain all the electrolytes from the battery. You may recycle it to manufacture washing powder or baking soda. It’s best to insert a fresh electrolyte at the end of the process.
  4. Fill the battery with distilled water up to 75% of the available volume.
  5. Next, add a few teaspoons of Epsom salts. Depending on the sulfation rate, you require anywhere between 36 grams to 240 grams per liter of water.
  6. Connect the battery to a trickle charger and turn it on. You should now see bubbles forming near the electrodes.
  7. Leave the setup for a few hours. Once the bubbles subside, turn off the charger and disconnect it from the terminals.
  8. Drain the solution out of the battery. Fill it with a fresh electrolyte that consists of an acid-to-water ratio of 35:65.
  9. Close all the caps and terminals of the battery. You can now charge it to total capacity and use it for its intended application.

Note: Since this method involves dealing with corrosive substances, it’s best to consider a few safety measures. Always use gloves during the procedure and conduct it in a safe environment, away from pets and children. Moreover, pour the electrolyte slowly as it can spill over to other equipment.

See full this video: Recover Lead Acid Batteries | Desulfate using Epsom Salts

What Is the Best Method To Desulfate a Lead-Acid Battery?

The best way is to use parts of both the methods mentioned above equally. You can use the Epsom salt solution and charge the battery with a battery desulfator. That way, you obtain the most optimum battery state without investing too much time. It can help you extend the lifespan of your battery far longer than either of the procedures alone.

How Do You Desulfate a Lead Acid Battery With Epsom Salts?

Epsom salt reacts with the solid sulfate crystals and dissolves them in a neutral solution, such as diluted water. Still, it requires some charge to activate the electrodes, which is why it’s essential to connect a battery charger/maintainer for the best results. It’s also the fastest method to revive a dead battery.

Frequently Asked Questions

What Voltage Is Needed to Desulfate a Battery?

You require at least 125% of the battery’s rated voltage to desulfate it. However, the current should be much lower, usually around 500 mA.

Can a Lead Acid Battery Be Desulfated?

Yes. There are multiple methods to desulfate a lead acid battery. Refer to the sections mentioned earlier in this guide.

Can You Mix Epsom Salt With Battery Acid?

No. Epsom salt is highly basic in nature. Dissolving it in a strong acid can cause an explosive reaction. In worst-case scenarios, it may lead to an electrical fire.

Can Old Lead Acid Batteries Be Restored?

Yes. You can restore old lead acid batteries so long as the electrodes remain functional. Too much sulfation requires you to swap out the electrodes entirely.

Can You Desulfate AGM Batteries?

Yes. You can follow the same procedure for both FLA and AGM batteries. The only difference is AGM batteries take longer to restore due to isolated cell compartments.


Desulfating lead-acid batteries are pretty straightforward. You can choose your preferred procedure depending on whether you have ample time or want to exercise maximum safety. We hope this guide provides you with a good idea of how to desulfate a lead acid battery adequately.


  2. How to Desulfate a Lead Acid Battery
  3. Recover Lead Acid Batteries | Desulfate using Epsom Salts



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