How to Check the Water Level in the Car Battery

It’s important to regularly check the electrolytic water level of your car battery (it’s really not just plain water) for two reasons: first, the solution will evaporate naturally. over time and second, each time the battery is charged, a small amount of the solution is electrolyzed into hydrogen and oxygen. Knowing how to safely test and replace battery water is an important part of car maintenance. Let’s start from Step 1 for detailed instructions on checking car battery water level and at the same time, ensuring the safety of both people and vehicles.

Table of Contents

Clean and open the battery cover

Identify the location of the battery. In most cases, you just need to open the bonnet to operate the battery. ^{[1] X Research Source}

Some batteries are located quite low in the engine compartment, behind the guardrail and in front of the car’s front wheels. Sometimes, you can access the battery from below and have to remove it for inspection and maintenance.
Most batteries from BMW, Mercedes Benz and a few others are located in the trunk, in a separate compartment.
The battery can also be located under the back seat, as is the case with some Cadillacs.

Cleaner. Before performing a battery water level test, clean the top of the battery and around the terminals. This is important to prevent foreign objects from falling into the compartments when opening the jar. And at the same time, a clean surface contributes to reducing or preventing corrosion in nearby metal structures. ^{[2] X Research Source}

To clean common dirt and minor rust, use a small amount of ammonia-based window cleaner. Spray water on the rag – do not spray directly on the battery , and wipe away any dirt. Paper towels can also be used, as long as they are replaced as soon as they begin to fall apart.
Heavy rust stains can be cleaned with a mixture of water and baking soda. Similarly, wet a rag and wipe, do not pour directly on the jar. Sometimes, you will have to soak the rag and wipe it several times. Finally, use glass cleaner to clean this baking soda solution. Leaving baking soda on the outside of the battery will speed up future corrosion of the terminals and nearby metal structures.
Don’t be negligent: always make sure the lid is tight while cleaning. Do not allow cleaning solution to drip or drip into the tank .
Note: If you wish, you can remove the battery from the vehicle before cleaning, servicing and reinstalling it later. Thanks to that, things can be safer, especially when the battery is not in a convenient location for manipulation. However, when that happens, you’ll have to restart some or all of the car’s electronics (clock, radio station setup, etc.). Also, usually when you don’t need to remove the tank, you will save a considerable amount of time.
We can also completely remove the terminals from the battery and dip it in a cup of very hot water. Hot water can remove rust and clean the surface of the poles. Make sure they are completely dry when reassembled.

Open the jar lid. On the top of the battery there are usually two rectangular covers that are used to seal the mouth of the compartment, which can be opened by using a small plastic knife or a light screwdriver. If the cap doesn’t come loose right away, slowly pry a few places around the lid.

Some batteries have six separate round caps instead of the above and can be opened by turning counterclockwise and then pulling them out.
If “maintenance-free” is written on the lid of the jar, the jar is not designed for opening. The manufacturer recommends that water cannot be added to these bottles, they simply need to be replaced when they are no longer in good working order.

Continue cleaning if necessary. Opening the lid can help reveal more stains on the top of the jar. Continue cleaning with a cloth moistened with glass cleaner.

At this point, don’t use baking soda. Use a small amount of glass cleaner and be careful that nothing (washing liquid, dirt, pieces of tissue paper, etc.)
Do not rush to skip this step – maintaining the cleanliness of the top of the battery will reduce rust later on. This is an important step in battery maintenance, helping to maintain a complete connection between components.

Check the liquid level in the battery

Compare the solution levels between the compartments of the flask. When you look down at each compartment through the mouth of the bottle, you can see the level of electrolyte solution contained inside. Usually, the amount of solution is uniform between compartments. ^{[3] X Research Sources}

In the opposite case, it may be because before, one compartment was accidentally filled in too much. This situation can be easily corrected by adding water at the time the solution level in that compartment has been reduced and returned to the normal range.
If the difference between the compartments is too large, it is also possible that the battery is leaking water or the tank shell is slightly cracked. In this case, you need to replace the tank with a new one. If no leaks can be found, add water to the highest safe level: use only distilled water and check again a few weeks later to see if the water level is still uniform across compartments.

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Identify whether the electrolyte solution is running low. The water level is considered too low if they do not fully cover the metal plate. When the plate is not completely submerged in the electrolytic water, the battery will not be able to operate at full capacity. ^{[4] X Research Sources}

When exposed to air, the destruction of the plate is only a matter of time.
If the electrolytic water level is only about 1cm below the top of the plate, adding just enough water to completely cover the plate can bring the battery back to life although the performance will decrease slightly (instructions for adding more water). presented in Part 3 of this article). If all else fails, you need to consider replacing the tank.
Low electrolyte water level may be due to too large charging source. So, if this is the case, you should consider checking your vehicle’s alternator.

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Identify what is a normal electrolytic water level. Typically, the electrolyzed water is about 3mm below the bottom of the shims (which extends from the mouth of the flask) or about 1cm above the top of the plate.

In this case, it may not be necessary to add water immediately. Just close the cap and check again in three months.

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Identify if the electrolytic water is at maximum. The highest threshold in the safe range is to touch the lower part of the shims.

Most shims have two small notches (threads) on the side, near the bottom. These two notches have the effect of making the water surface slightly cupped so that the naked eye can easily see when the water level hits the bottom edge of the tube. On the contrary, when the water is even lower, this meniscus will not appear.
A device that produces a meniscus of a liquid designed to signal the stop of the wedge. You may need a flashlight to see the water level and detect the meniscus more clearly.

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Note that this is the water level only for lead acid car batteries. Always follow the instructions of your battery supplier or manufacturer if they conflict with the information in this article.

Also be aware that batteries for golf carts, mops, and especially nickel cadmium tanks may require different levels of electrolyte water.

Electrolyte solution level adjustment

Use only distilled water to fill the battery compartments. Distilled water can be purchased at grocery stores. If the electrolytic water level is low (to expose the plates), add water to each compartment, just enough to flood the plates. Then, use the charger to fully charge the battery or just run the car for a few days, the battery will automatically be charged with current from the car. Only add water to the maximum level within the safe range, i.e. just touching the bottom of the shim, if the battery is fully charged. ^{[5] X Research Sources}

To ensure the correct amount of water is added last, use a clean funnel, sports water bottle, pump hose, etc. Be very careful not to let any dirt or cleaning solution get inside. jar compartment.
Using tap water, filtered water or any other type of water instead of distilled water will allow mineral salts and chemicals (such as chlorine in municipal tap water) as well as other impurities to penetrate and reduce its age. battery life. ^{[6] X Research Sources}

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If the battery is almost empty or completely dead, avoid adding water to the full level of the battery. If water must be added, it is best to add just enough to cover the plates (or nothing if already at normal level). ^{[7] X Research Sources}

When recharging a battery that is nearly empty or completely dead, the electrolyte level will rise and therefore a sufficient amount of space should be left (not necessary if the battery is fully charged before adding water).
The electrolyte level can also rise as the battery heats up.

Wipe up any spilled or spilled water and close the lid. Make sure everything is clean and put a clean lid on the jar.

If you accidentally add too much water, but it’s still not enough to overflow, it’s best to just stop adding water and close the bottle. If spilled on top of battery, don’t forget this is acid: avoid contact with skin or clothing.
Clean by wiping with a rag or paper towel. Avoid getting the rag or paper too wet and sticking to other parts of the vehicle or anything. Rub rags and paper towels in a bucket of water. Remember to wear gloves, do not let this water get on your hands.
When you’re done, throw the crumpled rags or tissues in the trash. Pour water into the sewage drain, taking care not to let the water run all over the floor. This will prevent the acid from sticking to other things. Finally, clean all that has come in contact with the electrolyzed water with a rag dipped in glass cleaner.
If the wedge is overhandled, visually inspect it weekly for a month for any spillage and clean as directed above.
The amount of sulfuric acid that is lost from the battery due to accidental spillage is likely to be only a small amount and will not significantly affect the operation of the battery. It’s best not to try adding more acid to compensate (excess acid will shorten battery life faster than lack of acid).

Take necessary safety measures

Protect your eyes with safety glasses. The electrolyte in the battery is a solution of sulfuric acid: you must avoid getting acid in your eyes as it can cause serious injury, even blindness. ^{[8] X Research Sources}

Contact lenses do not protect the eyes and can be a nuisance in the event of an accident. Regular eyeglasses are also not enough to protect the eyes because of the lack of shielding on the side.
Therefore, wearing safety glasses is essential. They can be purchased at hardware stores.

Protect hands with disposable gloves. Choose gloves that are resistant to sulfuric acid for at least a few minutes. These gloves can be found at hardware stores. ^{[9] X Research Source}

Natural rubber (latex) or vinyl gloves cannot withstand acids for long. If using them, replace them as soon as electrolyzed water is detected. If left for a long time, electrolyzed water can penetrate the glove and burn your hands.
Neoprene gloves can protect hands for an hour or more but are difficult to obtain from a regular parts store. Nitrile is different from neoprene. Nitrile is less resistant to sulfuric acid than natural rubber (latex) and should not be used.

Advice

If you don’t know what to do, ask a mechanic. Most auto repair centers can do it for you for free.
Pay attention to keep and clean the working corner when maintaining the battery.
Do not open the tank cap while the vehicle is running.
Make sure your eyes are protected. The acid in the battery can be blinding and is highly corrosive.
Wear safety glasses when checking and watering the battery.
Use a small plastic knife (about 2.5 cm wide) to pry open the lid of the jar. These knives can be found at hardware stores or paint stores. Otherwise, a screwdriver with an insulated handle can be used, but when prying, be careful not to accidentally touch the metal part of the screwdriver or any other metal object. This can create a spark and ignite the hydrogen gas in the battery.
Clean the battery. Stains will trap moisture and become conductive, especially stains with acid fumes that come out of the tank. Current flows to the outside of the battery through the stains, accelerating the corrosion of nearby metal.

Things you need

Protective eyewear
Glove. Preferably neoprene gloves. Natural rubber (latex) or vinyl can also be used. Nitrile cannot resist acid from the battery.
Wipes or paper towels
Distilled water
Sports water bottle, pump or funnel.
Ammonia based glass cleaner
Baking soda (optional – in case the battery terminals are heavily corroded)
2.5 cm wide flat plastic knife (optional) to pry off the battery cover or carefully use a screwdriver with an insulated handle.

Steps