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How to Make Acid for a Battery (4 Simple Steps)

If you want to make battery acid for your battery, you’ve come to the right place.

You can extend your battery’s life by replacing the battery acid. You can recondition a weak or old battery by making battery acid. As long as you can obtain sulfuric acid, it’s not difficult, but you must be extremely careful handling it.

To make acid for a lead-acid battery, dissolve sulfuric acid in water. The acid-to-water ratio is usually between 1:4 and 2:3 (20-40% sulfuric acid), depending on how much gravity you need.

I’ve briefly introduced sulfuric acid and battery acid, their danger, and how to protect yourself, explained how to make it step-by-step, and answered some questions below.

old broken automobile batteries
Old broken automobile batteries

Getting Started – Why Not Just Add Water?

When people refer to adding water to a battery, they typically talk about distilled water and adding it to a lead-acid battery low on electrolytes. The electrolyte in a lead-acid battery is a mixture of sulfuric acid and water. Over time, the water in the electrolyte can evaporate, especially if the battery gets hot.

When this happens, adding distilled water to the battery is possible to restore the electrolyte to its proper level. You should not use tap water, as it can contain minerals and impurities that can damage the battery.

Adding water does not replace the sulfuric acid that the battery needs to function, but it can help maintain the proper acid-to-water ratio in the electrolyte.

However, if the battery has lost acid (due to leakage, for example), simply adding water won’t help and could dilute the remaining acid and decrease the battery’s performance. In that case, adding more sulfuric acid to the battery would be necessary.

Battery Acid

The battery acid in lead-acid batteries is a mixture of sulfuric acid and water.

Sulfuric Acid

The acidic component is spelled “sulfuric” in American English and “sulphuric” in British English. Both refer to the same battery acid.

Sulfuric acid is a highly corrosive mineral acid with the chemical formula H2SO4. The acid is clear, colorless, odorless, viscous, and oily when pure, with a density of 1.84 Kg L-1 (nearly twice that of water) [Pavlov, 2017]. It is soluble in water at all concentrations. The dissolution reaction is highly exothermic, i.e., it produces a substantial amount of heat.

alert sign in red

Sulfuric acid is highly corrosive. It must be stored in a non-reactive container, such as glass. It can cause severe burns if it comes into contact with the skin. Skin and mucous membranes react very strongly to it. It can also burn through metal and plastic.

Also, be aware that battery acid easily absorbs impurities but is not flammable.

Sulfuric Acid in Lead-Acid Batteries

The mixture with water provides a concentrated form of sulfuric acid.

The sulfuric acid solution is placed between the lead plates in lead-acid batteries. It works as an electrolyte formulated by lead sulfate. The negative plate is a solid lead, and the positive plate is lead dioxide.

Therefore, the three active materials in a lead-acid battery are sulfuric acid, lead, and lead dioxide.

alert sign in red

Even when mixed with water, sulfuric acid is highly corrosive and can cause serious burns. Battery acid in the eyes can blind you. Always handle battery acid with extra care while wearing safety gloves.

Why We Use Battery Acid

We use battery acid, i.e., sulfuric acid, mixed in water because it has high electrical conductivity.

Making Battery Acid

Here’s how to make or prepare battery acid.

Step 1: Safety First

We MUST take precautions because sulfuric acid is highly corrosive and can burn the skin.

Even a single drop can cause severe burns. So, wear safety gloves, eyeglasses or goggles, and a facemask. Also, wear full sleeve clothing.

Step 2: Pour Water

Pour water into a clean plastic container.

We will make battery acid containing 20% sulfuric acid and 80% water. This would provide a 1250 gravity battery. Use clean distilled water so that it is free from minerals and contaminants.

Pour 8 liters of water into the container and add 2 liters of sulfuric acid. Pour the acid a little at a time to avoid a rapid and hazardous chemical reaction.

Step 3: Stir the Mixture

Stir the mixture well.

Leave it inside the container for around 8 hours to allow it to settle.

Step 4: Check the Gravity

Check the electrolyte’s gravity using a hydrometer.

It should be around the 1250 mark. If it is, the battery acid is ready to use but be very careful when pouring it into the battery.


Where can I get sulfuric acid from?

You can get sulfuric acid from laboratory material suppliers and chemical companies. Otherwise, you can make your own.

How can I obtain concentrated sulfuric acid from diluted sulfuric acid?

boiling sulfuric acid to get a concentrated form

Keep the diluted sulfuric acid in a glass container. Keep it covered to ensure no dust gets inside. Some water will evaporate over a few days, leaving you with a more concentrated form of the acid.

If you want the concentrated form sooner, boil the sulfuric acid in borosilicate glass (not ordinary glass) to evaporate the water quicker. You must only use this type of glass to minimize the acid fumes and protect the container from breaking.

When you notice white vapor rising while boiling it, let it cool down a little before adding water to make battery acid.

Can you use vinegar instead of sulfuric acid?

You might be tempted to use an alternative acid, such as vinegar if you cannot get hold of sulfuric acid.

But I don’t recommend that you consider any such alternative. Vinegar would react with the other chemical components, causing them serious damage. As a result, the battery will most likely not work anymore.

However, vinegar is useful for removing corrosion from the external surface of alkaline batteries.

How can I clean the corrosion due to the battery acid?

If you accidentally dripped some battery acid onto something made of plastic or metal (hopefully not your skin), apply a little baking soda. It will neutralize the sulfuric acid. Don’t put baking soda inside the battery. I’m only recommending it for cleaning corrosion from external surfaces.

What should I do if a drop of battery acid comes into contact with my skin?

Even if a small drop of battery acid touches your skin, you should seek medical aid immediately.


D. Pavlov. Lead-Acid Batteries. Science and Technology. A Handbook of Lead-Acid Battery Technology and Its Influence on the Product. Elsevier Science. 2017.

Old broken automobile batteries. https://pxhere.com/en/photo/399647

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About Alex Robertson

AvatarCertifications: B.M.E.
Education: University Of Denver - Mechanical Engineering
Lives In: Denver Colorado

Hi, I’m Alex! I’m a co-founder, content strategist, and writer and a close friend of our co-owner, Sam Orlovsky. I received my Bachelor of Mechanical Engineering (B.M.E.) degree from Denver, where we studied together. My passion for technical and creative writing has led me to help Sam with this project.

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