Cold does not usually kill a battery. It makes a tired battery’s weakness show: the engine is stiffer to turn, and the battery has less to give. Many “winter failures” are batteries that were already worn by summer heat, which AAA identifies as the main thing that shortens battery life.
Before winter
- Test it. Measure resting voltage with our voltage checker. OPTIMA advises recharging a battery that rests below about 12.4V.
- Check age. If it is past about three years, get it load tested. See how long car batteries last.
- Clean the terminals. Poor connections hurt most when starting is hard. See cleaning corrosion.
- Check the cranking amps your car needs. Use the CCA calculator as a starting point, but follow your manual.
During cold spells
- Switch off lights, heaters and the radio before you crank.
- Take longer drives now and then so the battery recharges fully.
- Carry a portable jump starter, and know how to jump-start a car safely.
If your battery is due, compare options in the cost calculator.
Why cold makes starting harder
In cold weather, a battery’s chemical reactions slow, so it can deliver less current, and the engine oil is thicker, so the engine needs more. The two combine, and a battery that coped in summer may fail in winter. That is why cold-weather battery failures are common even though heat does the lasting damage.
What CCA means for you
Cold cranking amps measure the current a battery can deliver at 0°F for 30 seconds while holding a minimum voltage. Your manual gives the minimum for your car. The CCA calculator gives a rule-of-thumb starting point from engine size, but the manual is the authority. Buying a battery with at least that figure matters more in a cold climate.
A winter routine
- Test the battery in autumn.
- Check the charging system if you have had warnings.
- Clean terminals and apply protector.
- Keep the fuel tank reasonably full and use the right engine oil, which also helps starting.
- Avoid repeated failed start attempts, which drain the battery. Wait a few seconds between tries.
- Turn off accessories before starting.
If the car will not start
Try a jump start or a portable booster: how to jump-start a car. If the battery is more than a few years old, test it afterwards and consider a replacement. Compare costs with the calculator.
Parking in the cold
A garage helps. If the car sits for a long time, use a maintainer: storing a car. EVs and hybrids lose range in the cold; their 12V batteries are affected too, so keep it tested.