Oleksandr Sadovenko/Getty Images You probably already know that the old ways of topping off battery water have become increasingly uncommon in modern cars, and most models have switched to maintenance-free batteries. Unlike conventional flooded lead-acid batteries (FLA) that require periodic electrolyte top-offs through filler caps, modern maintenance-free batteries feature sealed designs, often using lead-calcium-alloy grids and pressure-relief valves to significantly reduce water loss. As opposed to serviceable batteries, sealed batteries such as valve-regulated lead-acid (VRLA), Absorbent Glass Mat (AGM), or gel type batteries all combine oxygen with hydrogen ions at the negative lead plate into water, eliminating the need for checking electrolyte levels and topping up with distilled water. However, just because your battery says "maintenance-free," doesn't mean it requires no upkeep at all. Even in these so-called maintenance-free batteries, you might've seen the terminals getting gunked up with corrosion. Therefore, cleaning is certainly something we'd consider as a part of upkeep to extend a car battery's lifespan, as are visual checks for cracks, leaks, or bulges. While sealed batteries typically last longer than serviceable FLAs — these batteries aren't immune to sulfation, which is a scenario where lead sulfate crystals build up on the battery's plates, reducing its ability to hold a charge over time. To prevent this, Midtronics reckons it's important to keep batteries fully charged — especially if your car remains unattended for extended periods. Placing the battery on a trickle charger might also help extend its lifespan, but if you're off on a month-long vacation and can't be bothered with a trickle charger, you might even consider disconnecting the battery and storing it somewhere safe. Whether or not you want to call all this "maintenance" is up to you, but clearly, these batteries aren't something you can just plonk inside your car and forget entirely. How to properly maintain a maintenance-free battery Natallia Ploskaya/Shutterstock Professional shops have testing and diagnostic hardware to test if a maintenance-free battery is still functioning correctly. However, as far as a non-professional is concerned, the things you can do safely, according to AAA, are inspect for leaks, corrosion, and check the battery voltage using a digital voltmeter. Start off by unhooking the negative (black) terminal first, then the positive (red) cable, and optionally lift the battery off the car to visually inspect. If it is leaking, bulging, or looks damaged, replace it with a new one. Otherwise, check for voltage and clean the terminals before placing it back in the car. Use a mix of baking soda and water (or battery cleaners) and a wire brush to gently scrub away the corrosion. Once dry, remember to place it back in the right order — it's positive first and then negative. Since the sulphuric acid electrolyte inside your lead-acid battery can eat through concrete, it's important that you wear the right protective gear before you start maintenance work on your car's battery. Improper handling of these batteries can actually lead to serious injuries. But what about servicing? Although iFixit has a multi-step guide on how to check and refill a maintenance-free battery's electrolyte levels, the process is quite involved and requires drilling holes into the top of the battery, which is not something that's generally advised. So if you're not confident in your electrical/battery skills, it's best to leave such things to a trained technician.
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