In this article, we will show you how to safely check the water levels in your car battery. We’ll also show you how to refill your battery if the water level is low.

Checking the water level in your car battery is an important aspect of regular car maintenance that everyone with a vehicle should do. We recommend you check your battery’s water levels at least once every three months for a new battery and once a week if the battery is older than 1½ years.

All lead-acid batteries have water inside of them and over time, their water levels may go down. And a lack of water will reduce the battery’s power and can even shorten the battery’s lifespan over time. So to ensure your battery last as long as possible, this is very important to do regularly.

It used to be very common for car owners to check their car battery’s water level and top it off occasionally. However, most people don’t do this anymore because they aren’t aware this is something that should be done somewhat regularly.

But luckily, you’ll know exactly what to do by the end of this article…

So first, why does the water level (i.e. the electrolyte levels) go down in a car battery? Well, for two reasons:

  1. It evaporates naturally
  2. A small amount electrolyzes into hydrogen and oxygen every time you charge the car battery


Before you check your battery or refill it (like we’ll teach you in this article), it’s important you have these safety items:

Wear safety glasses when checking your car battery
  1. Safety Glasses
  2. Safety Gloves

Other items you need to have close by :

  1. Rags
  2. Distilled water
  3. Baking soda
  4. Flat head screwdriver
  5. Wrench
  6. Cleaning brush

Before you begin, PUT ON the Safety Glasses and Gloves.


Where to located your car battery in your vehicle

In most vehicles, the battery is usually located in the engine compartment. You will typically see it if you pop the hood of your car.

However, some manufacturers put the battery in the trunk or beneath the rear seats. So check those locations if your battery isn’t under the hood of your car.

To check and re-fill your battery’s water levels, you do not have to remove the battery if the top of the battery is accessible. But if the top of your battery is not accessible and needs to be removed, follow these steps:

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Removing the battery
  1. With an adjustable wrench loosen the bolt on the side of the negative clamp holding the cable onto the battery terminal. After this, repeat the procedure to remove the positive cable from the opposite terminal.
  2. A bracket or housing keeps the battery in position. To remove the battery, loosen the wing nuts or unbolt it.
  3. You can then lift the battery out of the car. When lifting, be prepared for the weight of the battery because car batteries are quite heavy.


The outside of the battery must first be cleaned before opening the battery so dirt does not get into the battery and contaminate the electrolyte fluid. This is very important otherwise your battery’s life can be shortened dramatically.

How to clean the battery:

  1. Make a paste of baking soda and water. It should have a thick consistency.
  2. With a rag, scrub the paste over the outside of the battery. This neutralizes corrosion and battery acid that is on the outside of the battery.
  3. With a cleaning brush (or old toothbrush) scrub the mixture over the terminals until they are free of corrosion.
  4. With a clean moist rag wipe clean any remaining baking soda from the battery.
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Rectangular covers can come off by prying them off with a Flathead screwdriver
  1. Usually there are six cell ports in an average car battery. Each cell has an electrode and electrolyte fluid. The ports will typically be protected by plastic covers. These will most likely be either two rectangular covers or six separate round covers that cover the cell ports.
  2. Rectangular covers can come off by prying them with a Flathead screwdriver.  The round covers will just twist off counterclockwise.
  3. With a damp rag clean under the covers. Please do not skip this step as it is beneficial for the battery. 
  4. Now that the cells are open, look into each battery cell where the electrode (i.e. the battery’s water level) is located.
  5. All electrodes should be completely covered with liquid.  Also, the level should be the same in all the cells.
  6. If you can see that the electrodes or the electrolyte levels are not the same level in each cell, you will have to refill the battery.


  1. In a fully charged battery that is relatively new, the level can be filled up to the bottom of the filler tube. In an older battery that is not in good shape, the water should cover the electrodes only.
  2. Add the appropriate amount of distilled water according to the condition of your battery. This is important – only add distilled water to your battery. Do NOT add tap water or other types of water.
    • *Pro TIP*  Use a small bottle container and funnel so that you can regulate the amount of distilled water you are adding to the battery. Being precise is important.
  3. You can then replace the battery covers. Some click into place by lining up the cell port covers and pressing down. And the round covers will have to be turned clockwise for them to tighten.

Once you have finished the procedure you can start your car. Great job! This simple procedure will help protect your car battery and prolong the life of your battery.

    4 replies to "How To Check And Refill Your Car Battery Water Levels"

    • […] favour SLA’s is because they require little maintenance. Unlike FLA’s that need to be checked regularly for water level, SLA’s that are used properly can be left […]

    • Jeff

      Really helpful. This is a good tutorial. More people need to be doing this to their car battery.

    • Peter Toye

      I check mine every 3 months

    • Sandra Daniels

      Thanks for the info, I never knew that you’re supposed to put water in your battery (I thought my ex was crazy when he told me to do that too). Turns out he was right, except he thought regular tap water was ok to use.

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