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Four Parts:Cleaning the Battery and Opening the PortsAssessing the Existing Fluid LevelsAdjusting the Fluid LevelsTaking Adequate Safety PrecautionsCommunity Q&A

It's important to regularly check the electrolyte (it really isn't just water) level in your car's battery, for two reasons: first, because it naturally evaporates and second, because a small amount electrolyzes into hydrogen and oxygen every time you charge the battery. Learning how to safely check and replace the water in your car battery is an important aspect of car maintenance. Start with Step 1 below for detailed instructions on how to check car battery water levels, while protecting both you and your car.