Inspect the battery regularly
Every few months, and before winter and summer, take a quick look at the battery. Check for:
- A cracked, swollen, or bulging case.
- Moisture or residue that could indicate a leak.
- Corrosion on the terminals and clamps.
- Loose cables, or a battery that moves in its tray.
Any cracks, bulging, or leaks are a reason to have the battery replaced.
Clean the terminals safely
White, blue, or green crusty buildup on the posts can reduce the electrical connection. Clean it carefully:
- Wear eye protection and gloves. Battery acid is corrosive.
- Turn the engine off. Disconnect the negative (black) cable first, then the positive. Check the manual for any vehicle-specific instructions, because some cars have electronics that are sensitive to battery disconnection.
- Scrub the posts and clamps with a wire brush and a mixture of baking soda and water, keeping the liquid out of the battery’s vent openings.
- Rinse lightly, dry thoroughly, and reconnect the positive first, then the negative.
- Some people apply a thin layer of dielectric grease or petroleum jelly to the terminals afterward to slow new corrosion.
Keep it secure and charged
A hold-down clamp prevents vibration, which can damage a battery internally. Make sure it is snug but not overtightened. Also keep the battery charged: a battery that regularly sits partly discharged tends to wear out sooner.
Driving and usage habits
- Take a longer drive from time to time so the alternator can recharge the battery. Constant short trips can leave it undercharged.
- Turn off lights, the stereo, and other accessories before shutting down the engine.
- Avoid using accessories for long periods with the engine off.
- Unplug chargers and dash cameras that stay powered if the car will sit for a while.
Serviceable batteries
Some older or budget batteries have removable caps that allow you to check the electrolyte level. If yours does and the plates look exposed, top up with distilled water only, and do not overfill. Many modern batteries are sealed and need no topping up.
Is it bad to leave a battery maintainer on all the time?
A modern smart maintainer, sometimes called a tender or float charger, is designed to be left connected and will reduce or stop charging when the battery is full. A basic trickle charger with no automatic control is different and can overcharge a battery if left on indefinitely. Check the device’s instructions, and use one that matches your battery type, such as AGM.
What kills a car battery the most?
There is no single answer, but common culprits include heat, repeated deep discharges, frequent short trips, parasitic drain, vibration, and a faulty charging system. Age eventually catches up with every battery. For typical lifespans, see how long car batteries last.
Test on a schedule
Once the battery is a few years old, have it load tested every year. Testing can catch a weakening battery before it leaves you stuck, and cold snaps in particular tend to reveal one; see why car batteries die in cold weather. If you notice slow cranking or dim lights, check our list of signs your car battery is dying.