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How to Troubleshoot an Overheating Car Battery

by Allen Moore

An overheating battery can present an extremely hazardous situation for anyone near the vehicle, as well as the vehicle itself. If an alternator’s voltage regulator is beginning to fail, or has failed, the alternator can begin to send too much voltage back to the battery, which in turn causes the battery to overheat. Once the battery overheats the electrolyte solution inside boils and ultimately the battery can explode sending battery acid in all directions. If you smell rotten eggs, notice your battery is swelling, or see steam coming out of it, your battery might be overheating.

Step 1

Turn the engine off immediately if you suspect the battery is overheating.

Step 2

Wait for the vehicle to cool down. Letting it sit overnight is best to ensure everything has cooled off completely.

Step 3

Put on your glasses and gloves, then open the hood and disconnect the negative battery cable with the battery cable wrench.

Step 4

Skip to Step 6 if your battery is maintenance-free. If it is, you may see the words “Maintenance Free” on the battery itself. If you don't see those words, check to see if there are caps on the top that you can remove to add water. If there are no removable caps, the battery is maintenance-free.

Step 5

Remove the caps and see if the water is low. The water should come right to the bottom of the lid, when the lid is closed. If the battery needs water, carefully pour in some distilled water. Use rags to immediately clean up any overflow; you don’t want the acidic water to drip onto other components inside your engine compartment.

Step 6

Use the socket set to remove the alternator. You will need to remove the serpentine belt first, with a belt tensioner tool. If you do not have a belt tensioner tool, you can use a socket wrench, but be very careful, as the socket wrench can allow you to over-torque the tensioner and break it.

Take the alternator to your local auto parts store and have it bench tested. Odds are, you will need a new one. Bear in mind, rebuilt alternators are likely to die soon after installation, so if you have the option, purchase a quality alternator built by the car’s manufacturer.

Items you will need

  • Safety glasses
  • Gloves
  • Battery cable wrench
  • Distilled water
  • Rags
  • Socket set
  • Belt tensioner tool

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