Written By Marina Dawson

If you are concerned about your battery’s performance and are unsure whether it is operating at full capacity, you’ll probably want to test the battery. One of the best and easiest ways to do this is by using a hydrometer which will read the state of charge in the battery fluid. Hydrometers are relatively inexpensive and easy to find, and are a must to keep on hand in your toolbox. If possible, try to get a hydrometer with a built in thermometer, as temperature extremes can have an affect on your reading, causing it to be inaccurate. A good hydrometer looks very much like a turkey baster, and in fact works in much the same way.

Before testing your battery, you’ll want to fully charge it and then let it sit for at least several hours, preferably about twelve. Because you’ll be dealing with volatile and toxic substances such as sulfuric acid, it is important to take all safety precautions prior to testing. Wear old clothing, long sleeves, and gloves. Polyester is known to be an acid retardant, so you might consider this when deciding on what to wear. Also, don’t forget eye protection, as you are dealing with a toxic liquid that could easily splash up into your face. You will also want some clean rags and a solution of baking powder and water available to clean up any acid spills.

When you are prepared for testing, remove the vent caps with a small screwdriver. You will now be able to test the battery fluid. Squeeze the bulbous end of the hydrometer and carefully insert it into the battery cell. Be careful not to touch the surrounding parts of the battery with the hydrometer. Once the tip is inside the battery cell, release the bulb to suck the battery fluid up into the hydrometer. You may wish to squeeze and release a couple of times to avoid air pockets. You can view your reading on the side of the hydrometer, which will tell you the charge of the battery fluid in that cell. You should then follow the same procedure for the rest of the cells in your battery. There should not be more than a .05 difference in the reading of these cells.

If you have a maintenance free battery, you will not be able to manually check the fluid in your battery. Instead, these batteries usually come with a built-in hydrometer that you can use to get a reading. The downside to this is that the hydrometer tests only one of the battery’s cells, so you could have a problem in a different cell and the hydrometer would not be able to tell you.

When you are finished, release the fluid back into the battery and clean the hydrometer using the baking powder solution. Also use this and your clean rags to clean up any acid spills on the battery or terminals. Be sure to close up the vent caps on the battery as they were before.

Testing of your battery should be done at least every three months during regular usage. If you are putting your battery into storage, you’ll want to test it before putting it away and then again when it is time to bring it out. Performing regular tests on your battery will provide you with important information about how it is operating, and will also eliminate the guesswork about when it is time to purchase a replacement.

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