How to Determine If a Maintenance Free Car Battery Is Bad Open the hood of the car and remove the battery cables with a wrench. Remove the positive (+) red cable first then the negative (-) black cable. Put on safety glasses and rubber gloves. Click to see full answer. Beside this, what are signs of a bad battery? Watch for these five telltale signs of a bad battery so you aren’t caught out in the cold! Dim headlights. Clicking sound when you turn the key. Slow crank. Needing to press on the gas pedal to start. Backfiring. Furthermore, is it safe to charge a maintenance free battery? “Maintenance Free” just means that you don’t have to top it up with distilled water regularly. It’s fine to charge it up – but I recommend you take it to a car spares store – they can test whether it’s worth charging, or if the battery has just reached the end of it’s life. In this regard, how long do maintenance free batteries last? Never performed any battery maintenance. Usually a car battery will last, on average, 36 months. If you take good care of it, and live in a temperate climate, 48 months might be expected.How do you test a sealed car battery? How to Test Sealed Lead Acid Batteries Test the battery voltage. Set the voltmeter dial to DC (direct current) volts. Place the voltmeter leads on the positive and negative battery posts. Charge the battery. Perform a high-rate charge test. Perform a slow charge test. Slow charge the battery for several hours.