How to desulfate a lead acid battery with epsom salt

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how to desulfate a lead acid battery with epsom salt

Before we answer the question of how to desulfate a lead acid battery with Epsom salt, it is important to first answer the question ‘what is battery sulfation’ and explain why it is a problem.

Before answering this let us understand few terms.

Sulfation: Battery sulfation primarily affects lead-acid batteries, and as such is the main cause of their premature failure.

Small sulfate crystals form within the battery over time. When a battery is overcharged, undercharged or kept at a low charge then the amorphous lead sulfate within is converted into a stable crystalline.

These crystals deposit on the battery’s negative plates while reducing the battery’s active material, which is important for good performance.

Sulfation in batteries is usually seen when we do not fully charge batteries, a common occurrence in everyday life.

Insufficient Charge

It frequently occurs because of low or variable load supply from a charger or an engine, which causes insufficient supply of charge to the battery.

Because of this, the battery’s active material is reduced, which in turn will negatively affect its performance.

Desulfation: Is the process of removing the troublesome crystals and restoring a battery to maximum performance. During this process, some of these lead sulfate crystals are broken down and absorbed into the charge cycle.

When we leave batteries unused for a long period of time they start to lose their ability to hold a charge. With time, the lead present in the internal plates of batteries combines with electrolytes and lead sulfate crystals are formed.

Whenever this happens, we must completely desulfate the battery and restore its ability to hold a charge. And so it can be said that Desulfation constitutes the reconditioning of a battery.

There are several methods of desulfating a battery, but here we are going to talk about how to desulfate a lead acid battery with Epsom salt, as it is the cheapest method and is available to all.

Safe removal of the Battery

As we know, batteries contain toxic and abrasive chemicals such as lead acid. So taking the appropriate safety precautions is essential.

1. Always wear protective gloves and safety goggles when handling the battery.

If necessary, using your mobile device take a picture of the battery arrangement in situ, so you can tell how it should be replaced.

2. If the battery is connected to any power source then disconnect it. Loosen all required nuts and bolts on the clamp that connects the battery cable with any power source.

3. Any screws or clips holding the battery rigidly in position should be removed using an appropriate screwdriver. Finish unscrewing the screws by hand so that you don’t lose them.

4. Remove the battery.

Performing the Desulfation Process with Epsom salt (Magnesium sulfate).

1. Firstly, we need to take approximately 200-250 grams of Epsom salts.

2. Secondly, using a thermometer to check the temperature, heat around half a liter of distilled water up to 150 degrees Fahrenheit / 65 degrees Celcius.

3. Now, add Epsom salt to the hot water and stir it until it has dissolved into a solution.

4. After putting on your gloves and goggles again (if you removed them), carefully remove the caps on the battery cells.

5. Sometimes the battery is sealed in such a way that the location of the battery cells is not obvious. If this is the case then it is necessary to locate the ‘shadow plugs’ that cover the battery cells.

These ‘shadow plugs’ are drawn or molded directly onto the body of the battery so that the location of the cells can be identified.

With great care, slowly drill through these outlines of each shadow plug to gain access to the cells.

6. Have a receptacle such as a bucket ready to take any excess fluid. If there is any fluid remaining in the battery then pour that fluid into the bucket. Remember to be extra careful as this fluid will contain sulfuric acid which is highly corrosive.

Baking Soda

To make the liquid safe pour a generous amount of baking soda into the fluid. This will neutralize the acid. To dispose of the neutralized acid simply pour away into an outside drain. This is safe to do because we have already neutralized the fluid using the baking soda.

7. Using a plastic funnel, pour your Epsom salt solution into each individual battery cell until the cells are full. Replace and tighten the battery caps on the battery. If you drilled holes into a sealed battery, use plastic plugs to seal the holes.

8. To ensure that your Epsom salt solution is evenly distributed, shake the battery gently.

9. Now, we are finally ready to desulfate your battery. This is achieved by charging the battery to capacity using a battery charger. Connect the positive cable to the positive terminal and connect the negative cable to the negative terminal. However, always remember to follow the instructions that accompanied your charger – because chargers are all different.

Finally, it is worth remembering that it is much better to maintain your lead-acid batteries properly from the start, so that little or no sulfation occurs. This means keeping the batteries fully charged whenever possible, especially before and during storage, and, for flooded batteries, performing periodic equalization charges.

If a battery is stored at room temperature or has been disconnected, it should be fully charged at least once every six months.


Extreme caution shall be exercised while performing this procedure since the battery contains sulfuric acid, which is highly corrosive and can cause serious injury.

Only competent people should attempt the procedure described in ‘How to desulfate a lead acid battery with Epsom salt’.

To go see our review of Best Battery Chargers, click here 

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Steve Brown


Steve is a gadget enthusiast who's always been intrigued by batteries. The founder and editor of Battery Chargers Info, he's assembled a group of like-minded experts to cover every facet of portable power His aim is to help you learn more about your favorite gadgets and their batteries so you can maximize both their performance and their life. Follow him on Twitter: @batterycharge1

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