Is Car Battery Acid Dangerous On The Skin?

Contacting a battery acid with your skin is not the big problem but other eyes are yes.

I’ve heard so many stories about the effect of car battery acid on the skin, some outright scary, others more comforting. To be on the safe side, I did my own sleuthing. One of these days I may have to deal with my car battery. I am not a mechanic, but for sure, I can do a DIY inspection of the water level of my car battery, and top it off if needed. The results of my detective work are quite interesting, and I’d like to share it here.

Is car battery acid dangerous on the skin? No, car battery acid is not hazardous to the skin, but it is an irritant. If it touches your skin and you leave it there too long, without washing or flushing it off, it will cause itching, irritation, and dryness but won’t severely burn the skin.

I’m sure this comes as a surprise to you. It is common knowledge that acid is a dangerous substance that can burn human tissues and other organic matter.

What Is The Acid In Your Battery?

In general, battery acid refers to any acid found in a chemical cell or battery, but mostly for acid in a lead-acid battery like that of a car battery. The acid in a car battery cell is diluted sulfuric acid – a mixture of sulfuric acid and water, with only 30% to 50% of sulfuric acid content.

It is the concentrated sulfuric acid that is highly corrosive and with oxidizing and dehydrating properties. If it comes in contact with the skin, it can bring about severe chemical burns and also slight thermal burns.

Adding water to undiluted sulfuric acid will result in instant heating of the acid, generating hazardous steam and a shower of hot concentrated sulfuric acid that could burn the skin. That’s why what is considered the right way of mixing sulfuric acid with water is to add the concentrated sulfuric acid to the water rather than the other way around. Add the acid to the water slowly until the correct proportion is reached and then allow the solution to cool. After that, the car battery acid called the electrolyte can no longer burn the skin.

However, the sulfuric acid in your battery, although already diluted, is still corrosive and more dangerous than acids in other battery systems. If you get it in your eyes, it could result in blindness. If you swallow it, your internal organs can be damaged and could even lead to death.

What Should You Do If Car Battery Acid Touches Your Skin?

When the battery acid comes in contact with your skin, it won’t burn you. but it could cause itching and irritation, especially if you have an open wound or lesion. And, it could still bore holes on your clothing.

What you need to do if a spill touches your skin is to flush the affected area with tepid running water (tap water will do) for about 20 to 30 minutes. Flush it continuously until the irritation disappears. If necessary, repeat the flushing until all signs of soreness are gone. If the acid solution spills on your clothes, immediately remove your clothes and thoroughly wash the skin underneath.

It is urgently important to use a generous amount of water for flushing the affected area to further dilute the acid. If you only splash the irritated skin with a dash of water, you may be worsening the condition without lessening its potency. If you spill car battery acid on your clothes, you can neutralize its effect by using a weak alkaline compound.

Why Is There Acid In Your Car Battery?

The best way to answer this question is to discuss in detail the construction and the electrochemical reaction of a car battery.

Majority of car batteries being used today are rechargeable lead-acid batteries. These batteries are usually 12-volt batteries consisting of six cells coupled in a series. A single cell can generate approximately 2.1 volts. Thus a 12-volt battery produces 12.6 volts when fully charged.

Each cell of a battery has two lead plates, a positive and negative plate, separated by a separator and immersed in a liquid solution known as the electrolyte. The plates are coated with what is called active materials. For the negative plate, the coating is sponge lead while the positive plate is coated with a lead dioxide paste. The electrolyte is the battery acid, and as mentioned earlier, consists of sulfuric acid and water.

In producing electricity, car batteries convert chemical energy into electrical energy by making use of an electrochemical reaction between the electrolyte and the active materials of the plates. The electrolyte holds charged hydrogen ions and sulfate ions. The hydrogen ions are positively charged while the sulfate ions have a negative charge.

When you put a load across the terminals, the battery is being discharged. Some of the sulfate ions in the electrolyte are drawn into the negative plates where they relinquish their negative charge to become electrons. The leftover sulfate ions in the electrolyte merge with the positive plate’s active material (lead) to form lead sulfate which now becomes an electric insulator.

The active material (lead oxide) of the negative plate reacts with the hydrogen ions to form water. This process weakens the electrolyte and reduces it to water. Direct current (DC) is created when the electrons flow through the electrical load from the negative side of the battery and return to the positive plate.

The ions circulating in the electrolyte create the current flow. But as the battery discharges, the ions in the electrolyte lessens and the solution is turned into water. The positive plate also becomes coated with sulfate, reducing the surface area of the active material that will accept the electrons back. At this stage, the battery needs to be recharged.

When Does A Battery Need To Be Recharged?

Your car battery is responsible for cranking up and starting your engine. Once the engine is running, the alternator takes charge of powering the electrical system of your car as well as charging your battery. That’s why an alternator is called a car’s electrical charger.

Technically, if you have a healthy battery, you don’t have to recharge your battery from an outside source. However, factors like age, parasitic drain, and poor driving habits, among others drain your battery. When these factors render your battery unable to hold a charge making it weak or flat, then it becomes necessary to charge it from an external source.

Poor driving habits (other factors are discussed in another article) is one reason why a car battery would need to be recharged by an external power source. When you only drive short distances, the alternator is not given the time to recharge your battery fully. This condition is aggravated in winter when you use power-hungry car accessories such as a heater, window defroster, heated seats, windshield wiper, and more during these short trips.

This combination of only driving short distances and excessive power demand is deadly for your battery. One morning, you may find yourself stranded at home or worse, on a highway, because your car won’t start and the battery is dead, then you will need to recharge your battery. (Wonder if the car battery recharge itself?).

The Charging Process

Charging reverses the battery’s electrochemical reaction. This time, the electrical energy from the charger is converted into chemical energy. Take note, your battery stores chemical energy and not electricity. The chemical energy is converted into electricity to power your engine.

During the charging process, the electricity supplied by the charger creates electrons at the negative plate that attract the positive hydrogen ions. The hydrogen and lead sulfate react together to form lead and sulfuric acid. Once the sulfate is almost consumed entirely, hydrogen emanates from the negative plate. Lead dioxide again forms on the positive plate as oxygen in the electrolyte reacts with the lead sulfate.

When the battery is nearing the fully charged state, sulfate is reduced to a point when it could no longer continue with the reverse electrochemical reaction. This is called a battery’s natural absorption rate, where the charge current can be supplied without the battery overheating or the electrolyte breaking down into oxygen and hydrogen. Overcharging occurs when the battery is charged more than its natural absorption rate.


Car battery acid on the skin will not give you much grief. All it can do is irritate your skin, not burn it. The sulfuric acid in your car battery is already diluted, and its potency has already been reduced significantly. It is the undiluted or concentrated sulfuric acid that can do you a lot of harm.

However, even if the acid in the electrolyte can’t do your skin severe injury, it is still recommended that you take extra precaution when working on your battery. Wearing protective gears such as rubber gloves and safety glasses or goggles is a must. Your skin may not be severely affected but having the acid in your eyes is another matter.