Updated at: 17-07-2022 - By: Lucas

Batteries in cars might fail if the electrolyte level is not checked regularly. Battery capacity will quickly decrease and there is a high probability that it may fail altogether during the winter months. So, what are our options for maintaining the electrolyte level in the battery?

Why is the car battery’s electrolyte level important?

Lithium-ion batteries use an electrolyte composed of 65% water and 35% sulfuric acid as their primary electrolyte. When recharging a battery, the electrolyte may boil, especially if the temperature outside or beneath the hood is too high.

Acid has a low evaporation rate since it is nonvolatile. As a result, it is important to note that water evaporates rapidly. There is a decrease in the electrolyte level and an increase in the density of the electrolyte as a result.

Why you should add water to a car battery?

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The electrolyte level’s typical density is 1.29 g / cm3. Boiling water increases both density and acidity. A lack of water will harm the battery plates, causing them to wear out considerably more quickly.

When the electrolyte level is normal, adding water to your automobile battery ensures the battery’s efficiency and performance.

What type of water should you add to the car battery?

For your battery, distilled water is the only type of water you’ll need, as tap water and certain bottled varieties may include minerals and other elements that may corrode the components. Hydrogen and oxygen are the only two contaminants in distilled water.

When to add water to the car battery?

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It is possible to check the electrolyte level in a battery, but the first step is to take a closer look at what’s inside of the battery.

A specialized indicator can be seen on some batteries. It displays a variety of states.

  • Normal, low electrolyte level. In this case, you need to add water.
  • Low electrolyte density, here you need to charge the battery. 

Some batteries have a minimum and a maximum voltage. The relatively transparent shell of these batteries makes it possible to visually inspect the electrolyte level.

By removing the battery and removing the battery’s little covers, you may check the battery level. There is a particular indicator on some batteries that indicate that the electrolyte should not cover more than 0. 5 cm (0. 196 inches). If you don’t have an indication, you can use the plates’ immersion in the liquid as a guide.

Battery electrolyte and density should only be checked after the battery has been fully charged at a battery charger!

What is the normal level of the electrolyte in a car battery?

The electrolyte level should be between 15 and 20 millimeters (0.59 and 0.78 inches) above the plate edge. This indicates a low electrolyte level that needs to be restored as quickly as possible.

Hydrometers and refractometers are the best tools for the job. Most car parts stores carry these instruments, and they’ll come in handy for checking other fluids as well.

The electrolyte status can also be checked by measuring the level, which must be clear. It’s time to buy a new battery if the liquid is not clear or dark.

How much water is added to the car battery?

There is a direct correlation between a battery’s capacity and the amount of electrolyte it holds. Furthermore, the volume of the battery varies from manufacturer to manufacturer and is dependent on the design. Batteries of various capacities are shown in the table below.

How to add distilled water to a car battery?

Follow these simple procedures to properly fill the battery with water.

  • Clean the battery on the surface to avoid dirt and other substances entering the battery when you unscrew the plugs. Before that leave the battery at room temperature for approximately 7 hours;
  • Unscrew the plugs and check the electrolyte level as I described above;
  • If you need to add distilled water, add it carefully. If you added a larger amount, remove it using a syringe.
  • Screw the plugs back and leave the car battery for at least 7 hours because mixing the water with acid takes some time;
  • Charge the battery, but if you see that the electrolyte boils, charging should be stopped;
  • Measure the electrolyte density with a hydrometer. The normal level should be 1.29 g / cm3. 


Water can be added to a car battery to keep it working properly and extend its life. If you add anything other than distilled water to the battery, you run the risk of causing chemical reactions that hasten the demise of the battery’s plates, therefore only use distilled water.

Be careful when choosing some batteries and they are labeled as maintenance free because most of them are not. Batteries have their caps tucked under the battery label on the sticker. Simply removing the cover reveals the battery caps.

Batteries that don’t have caps on their surface are indeed maintenance free, and they don’t need to be replaced until they’re dead.

To avoid damaging the battery, do not add more water to it than it is required, as this will reduce its capacity. The battery’s power will be diminished since the electrolyte density will be reduced. In the winter, this reduces its ability to withstand freezing temperatures.

Fortunately, as I said before, there is a very simple method for reducing the surplus water. When you add sulfuric acid, you don’t have to worry about it diminishing right away because this process is incredibly slow.