Why the first freeze finds the weak ones
Cold slows the chemistry, so a battery delivers less power at 20 degrees than it does at 80. At the same time, cold oil makes the engine harder to turn. A strong battery has plenty of margin. A battery that came out of a 100-degree summer with much less capacity doesn't. It started the car all fall and gives up on the first hard-freeze morning.
It also explains why weak batteries tend to fail on the same morning. They all face the same cold at the same time, and the ones the summer wore down are the ones with no margin left.
Starting a weak battery on a freezing morning
If the car is slow, a few habits give it its best chance:
- Turn everything off first: the heater fan, the defroster, seat heaters, lights and the radio. Let the starter have all of the battery's power.
- Crank for about ten seconds at most. If it doesn't catch, wait around half a minute before you try again. Long cranks overheat the starter and drain what is left.
- Stop after a few attempts. Cranking again and again on a weak battery usually makes it worse.
- If it starts, don't shut it off right away. Let it run, then drive it instead of idling, to put some charge back.
When a frozen battery shouldn't be jumped
A badly discharged battery can freeze in a hard freeze. Its liquid has more water in it than a full battery's does, so it freezes at a higher temperature. A frozen battery can crack or bulge.
If the case looks swollen, cracked or wet, or you can see ice, don't try to jump or charge it. It needs to be replaced.
Getting ahead of the freeze
When a freeze is in the forecast, take stock. If the battery is three years old or more and has been slow to start, replace it on a day that suits you instead of at 6 a.m. on an icy driveway. Park in a garage if you have one. A longer drive once a week keeps the battery charged between cold nights.
Check the basics while you are under the hood. Clean, tight terminals matter more in the cold, because a poor connection costs the starter current at the moment it needs every bit. Cold-weather problems rarely come from one cause. A weak battery, a loose clamp and an unused car stack up.
If it won't start anyway
Dispatch is open 24/7, 365 days a year. A jump start is $49–$75, plus the $19 dispatch fee, charged once, and a battery replacement is $239–$255 for eligible vehicles and batteries, installation included. Arrival averages 30 minutes, with the actual time depending on location and traffic. We text or call when the driver is on the way. Wait inside the car where it is safe, and hold off on more cranking in the meantime. Each long attempt drains what the battery has left and makes the jump harder.
Common questions
Yes, a badly discharged one can if the temperature drops far enough. A fully charged battery is much harder to freeze.
A battery delivers more power when it is warm. A weak one can manage on a mild afternoon and fail at dawn, when the temperature is lowest.
Usually, if the battery isn't frozen or damaged. A cold battery takes a charge slowly, so a longer drive afterward matters more than usual.