Winter Driving and Your Car's Battery

Few things are more frustrating than a car that won't start on a freezing morning. Winter is when weak batteries finally give up. A little attention in the fall and through the cold months can keep you from needing a jump in a parking lot.

Why cold weather is hard on batteries

Two things happen at once in winter:

• The battery delivers less power. Cold slows the chemical reaction inside a lead-acid battery, so it can't produce as much current.
• The engine needs more power to start. Engine oil thickens in the cold, making the engine harder to crank.

Less power available plus more power needed is a bad combination. Heat damage from summer often plays a role, too. A battery weakened by hot months may work fine in fall, then fail on the first cold snap.

Warning signs of a weak battery

Watch for:

• Slow cranking that sounds labored, especially first thing in the morning
• Clicking when you turn the key or press start
• Dim headlights or interior lights at startup
• Battery or charging warning light on the dashboard
• Electrical glitches, like a radio that resets or a flickering screen
• Corrosion on the battery terminals
• A swollen or bulging battery case

Many modern cars also show messages about low battery or reduced electrical features.

Test before winter hits

You don't have to guess. Many auto parts stores and repair shops test batteries for free or a small fee. A proper test checks the battery's ability to deliver cranking power, not just its voltage.

It's also worth having the charging system checked. A failing alternator can drain a good battery and make it look like the battery is the problem.

If your battery is getting older, replacing it before winter is often less hassle than replacing it after it strands you.

Habits that help in cold weather

1. Drive long enough to recharge. Short trips don't give the alternator time to replace the energy used to start the engine.
2. Turn off accessories before shutting down. Headlights, heated seats, and rear defrosters add load at the next start.
3. Park in a garage when possible.
4. Keep terminals clean and tight. Corrosion and loose connections reduce current.
5. Use a battery maintainer if the car sits for long stretches.
6. Avoid leaving devices plugged in if your outlets stay powered with the car off.

Jump-starting safely

Keep jumper cables or a portable jump starter in the car during winter. When jump-starting:

• Follow your owner's manual, since some vehicles have specific jump points
• Connect positive to positive first, then negative to a bare metal ground point on the dead car
• Keep cables away from moving parts
• If the battery case is cracked, frozen, or leaking, don't jump it

If your car needs a jump more than once, have the battery and charging system tested.

Hybrids and EVs

Hybrids and electric vehicles still use a 12-volt battery to power electronics and start up their systems. If that small battery dies, the car may not turn on, even if the main high-voltage battery is charged. Winter range for EVs is a separate topic, but don't overlook the 12-volt battery.

Is a battery covered?

Car batteries are usually treated as maintenance or wear items. Most vehicle service contracts don't cover them, though the battery itself may come with a separate replacement warranty from its maker. The alternator and starter are a different story. These are often covered under electrical components in higher-tier plans. Many plans also include roadside assistance for jump-starts, but not all do.

Learn more about what service contracts cover on our coverage overview.

How Warranty Wizards can help

We help you compare plans from third-party providers and explain which ones cover starting and charging parts, and which include roadside help, before you buy. Get a free quote at /get-a-quote/.