Car battery problems in cold weather

Written by joshua smyth
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Car battery problems in cold weather
A freezing day is a terrible time for your car not to start. (dirty car image by Alexey Klementiev from

Car batteries need to be strong enough to start frozen engines and run heating systems. The cold can degrade high-quality batteries and render low-quality batteries useless. Keeping your car well-maintained before winter sets in is the easiest way to avoid starting trouble on cold mornings. Every winter driver should own simple tools and learn basic techniques in order to diagnose and repair battery problems.

Skill level:

Things you need

  • Electric battery blanket
  • Block heater
  • Trickle charger
  • Screwdriver

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  1. 1

    Listen to the sound of the engine if it turns over repeatedly without ignition. The battery will most likely not be damaged but the fluid in batteries can freeze. This freezing causes them to lose function in the cold, but the battery will thaw with the application of heat. Getting a jump start from another vehicle will start your engine and permit the alternator to send current to the battery. This will warm the battery and allow it to start charging again.

  2. 2

    Read your car's voltmeter; this is the dial on your dashboard with a small drawing of a battery. While your car is moving it should read between 14 and 14.5 volts; it may drop if you are running many electrical devices at the same time. If the reading drops below 12, the battery is discharging to power your car's electrical system. Thirty minutes of driving are required to warm the battery and allow the alternator to begin charging during periods of extreme cold.

  3. 3

    Clean the car's spark plugs and make certain the alternator is working. If the plugs and alternator are functional, starting problems or electrical system malfunctions can often be traced to the battery. A handheld ammeter will confirm a battery problem. Touching the red and black contacts of the ammeter to the matching terminals on the battery will indicate if current is flowing.

  1. 1

    Install an electric battery blanket. Detach the battery cover from its mounting brackets with a screwdriver. Lift off the cover, pull the battery out and wrap it in the blanket; leave the battery's contacts exposed. Use a twist tie to keep the blanket tight around the battery. Put the battery back in place, then replace the cover and screw it onto the mounting brackets. The blanket will have a cord with a plug. Run this cord out of the engine compartment to a wall outlet. The blanket will produce enough heat to keep the battery fluid from freezing.

  2. 2

    Mount a trickle charger near your car battery using the brackets that come with it. Wrap the red and black wires of the charger around the matching terminals on the battery. Plug the cord into a wall outlet. The charger will deliver enough power to the battery to keep it from freezing.

  3. 3

    Mount a block heater next to your engine block. Plug the cord into a wall outlet near the car. The heater will keep the engine block from freezing, making it easier for the car to start when the battery is weakened by cold.

  4. 4

    Avoid running the radio, the heater and the defogger at the same time. Running these devices simultaneously will use up all the power coming from your car's alternator and prevent the battery from charging.

  5. 5

    Turn off the heat and radio while the car is idling. And engine at idle will not be putting out enough power for the alternator to both charge the battery and power electrical systems.

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