Battery Acid vs. Distilled Water

The car battery is a crucial component, which powers the electric motor system, which starts the combustion engine. As with all car parts, maintenance is necessary for it to serve you well. The good thing is that it is not challenging to take care of the battery. Cleaning the electrodes and refilling electrolytes are the main things to do. Focusing on replenishing the fluid, we have the battery acid vs. distilled water discussion on our hands.

The lead-acid battery produces an electrical charge from the reaction of sulfuric acid and leads ions. The effect of heat and gassing leads to water loss; hence, the need for refilling. So which liquid should you use? Keep up with us as we look at the best solution.

Battery Acid

Battery acid, as the name implies, is the acid present in automotive rechargeable batteries. The acid of choice is sulfuric acid, acts as the electrolyte in the battery, and is in diluted form. The dilution comes from mixing this acid with water to drop its concentration to around 30% or 50%; thus, it is less volatile.

what is the ratio of acid to water in a battery

The Structure of a Lead-Acid Battery

The acid-water mixture makes the ions more liberal, leading to enhanced conductivity. The battery acid reacts with lead electrodes. They are conductive plates located on opposite sides of the battery. There is the negative electrode, which is the anode, while the positive one is the cathode.

The anode sends electrons to the circuit, whereas the cathode receives the electrons. The former is a sponge lead construction, with the latter built from lead dioxide. A separator acts as an insulator and prevents the electrodes from coming into contact, as it may lead to short-circuiting.

Back to the acid, on discharge, it decomposes and becomes more like water. The hydrogen ions from the acid will mix with the oxide ions from the lead dioxide. This is an exergonic process, which means there is a positive flow of energy in the system.

Another process that happens during the battery discharge is the release of sulfate ions, which coat the lead electrodes. This action reduces the surface area under which further electrochemical reactions occur.

When charging, you reverse the process and rearrange the composition of the acid. It converts electrical energy to chemical energy for storage.

Can I refill car battery with acid? You should never add acid to the battery unless it is totally dried up. You should never try this because sulfuric acid is very volatile and is a dehydrating agent. It can cause burns and other severe injuries if not handled properly.

On where to buy sulfuric acid for batteries, there are stores that deal with chemicals that stock it. The stores will give you pre-diluted acid, which is suitable for your battery.

If you decide to refill battery acid yourself, you need to have protective clothing like gloves and protective glasses. They will shield you from injuries.

How much acid should be in a battery? With the battery secured in its box, attach a tube or funnel to the inlets. Make sure to fill the acid until it fully covers the plates. Firmly secure the caps, and the battery is ready for use.

Distilled Water

Flipping the coin on the battery acid vs. distilled water discussion, we have the latter. When the electrolyte levels diminish, you refill it with distilled water, also going by deionized or demineralized water. This water goes through distillation to do away with minerals that may get into the way of the battery’s electrochemical process.

When should you pour distilled water into the car battery? Add more water when the electrolyte levels drop. The problem is knowing if the levels are down. Some people physically check the amount, which can be pretty exhausting. The good news is that there is a solution in the form of a level indicator.

You install this device behind the battery plug. It has LED lights, which will light up in a specific color to show you if the water level is alright or low.

Can I use tap water in a car battery? Tap water contains several mineral impurities which can interfere with the chemical process in the battery. Never use tap water on your battery, as it may lead to its deterioration.

A low water level is among the causes of the battery not holding charge.

Battery Acid vs. Distilled Water Differences

Battery acid and distilled water differences are very evident, seeing that they have different chemical properties. The obvious contrasting point is that battery acid is sulfuric acid, diluted with purified water. The result is a 15-30% concentration, which can go up to 50% in some cases.

Distilled water is water that goes through demineralization to remove mineral impurities that can affect the electrochemical process. You will find battery acid in the battery when it is new. When the acid volume drops, do not add more acid. Instead, you replenish it with distilled water.

how to make battery acid

Frequently Asked Questions

Q: Can I Use Distilled Water Instead Of Battery Acid?

Battery acid allows for the conversion of chemical energy to chemical energy. If there is not enough acid, you do not fill it with more acid, as it is hazardous. Use distilled water instead. A rare occasion where you can go for more battery acid is if it spills. Exercise care when pouring acid into the battery due to this chemical’s volatility.

You cannot swap battery acid for distilled water if there is no acid in the battery. The acid is vital as it enhances the electrochemical properties of water.

Q: Should I Add Water Or Acid To My Battery?

You have to regularly check on your battery electrolyte levels to see if the levels are alright. A battery water level indicator will help you monitor the amount of electrolyte you have. If low, you go for a bottle of distilled water. Never add acid to the battery, as it is dangerous, and you may degrade the battery. This action can affect its charge holding capability.

Always go for water unless the battery is dry with no electrolyte remaining.

Q: How Does Distilled Water Become Battery Acid?

When the battery electrolyte runs low, you should top up the fluid with distilled water. The diminishing level is due to gassing and heat, which reduces the acid’s water content. In this essence, adding water boosts the electrolyte level. The mixture of water and distilled water is reversible, forming a hydronium and sulfate ion.

Q: Why Should You Not Drink Distilled Water?

Distilled water lacks essential minerals that your body needs, such as calcium, magnesium, sodium, and potassium. The lack of minerals will give it a flat taste, which you may not like. The other downside of distilled water is that it may draw minerals from your body due to its lack of minerals, mainly affecting teeth. It may lead to weakened teeth.

Q: Can I Change The Acid In My Battery?

Changing acid battery is not advisable, though there are situations that may call for it. For example, if the acid spills and there is no remnant. The other scenario is where you have tainted electrolyte. If contaminated with dirt or minerals, the battery may have functional problems.

When doing the acid change, always put on protective gear like gloves, overalls, and glasses because the acid may cause injuries.

Q: Can You Put Too Much Distilled Water In A Battery?

Overflowing distilled water can have serious implications on your battery. If it overflows, it can cause some parts to wear fast. In addition, over-diluting the electrolyte can lower its performance.

Q: What Happens If You Add Acid To A Battery?

Dipping electrolyte volumes call for a refresh. You need to bring out a bottle of demineralized water to increase the battery’s fluid levels. You should never add acid to a battery with acid. This action may lead to the degradation of the battery, lowering its performance.

Final Words

A low battery fluid level is a common problem that calls for distilled water. After going through this presentation, you have a clear grasp of the battery acid vs. distilled water discussion.

Do not forget to perform other maintenance practices like cleaning the battery and change it every 4-6-years. If you want a change, go for top battery brands that will give you excellent service.


Hi there, I am R. Hasan Tito, a mechanic, and owner of this website. My friend and I created this website to share our knowledge, expertise, and experience with our fellow mechanics' community and car users. I am a specialist and certified automotive mechanic (Both Heavy Commercial and Private Cars). I worked as a Mechanic and Mechanic Supervisor for over fifteen years at Global Rebound Automotive companies - Toyota, TATA, BMW, Nissan, TVs, and Others. Now, I enjoy my new role of leading a team of automotive experts (in their respective fields) and publish new content on a regular basis on my website and social media.

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