Why Desert Heat Kills Car Batteries

How does heat damage a car battery?

A conventional 12-volt car battery is a box of lead plates in acid. AAA explains that heat speeds up corrosion of the battery’s internal grids, which reduces its capacity and the power it can deliver to start the engine. Interstate Batteries, a battery maker, says the same: heat speeds corrosion, cuts starting capacity and shortens battery life.

It is far hotter under the hood than outside. AAA notes that under-hood temperatures can top 200°F. In Lancaster, NOAA’s 1991–2020 normals at Fox Field show average highs of 97.6°F in July and 97.8°F in August, and about 36 days a year at 100°F or more.

How long does a battery last in the Antelope Valley?

Shorter than in a cool climate:

• AAA says a battery typically lasts three to five years, and that about three years is more typical in southern locales.
• AAA’s Mountain West Group says heat can cut battery life to as little as two years.
• Consumer Reports, citing AAA, reported in 2019 that batteries last 58 months or more in the far north but under 41 months in the south.

So a battery that came with the car, or one you bought three summers ago, is worth testing now.

Why does a heat-damaged battery die on a cold morning?

Because cold exposes the damage. A battery weakened over the summer can still start the car on warm days. Then the temperature drops.

Interstate Batteries says cold cuts battery strength by about 35% at 32°F and up to 60% at 0°F, while the engine needs nearly twice as much power to start. It also says heat damage often shows up later, when cold weather makes the engine hard to start.

The Antelope Valley has both stresses. Fox Field averages about 68 nights a year at or below freezing, most of them from November through February, with about 20 in December alone. That is how a battery that got through August can quit on a frosty December morning.

What are the warning signs of a failing battery?

AAA lists these:

• slow cranking when you start the engine
• a clicking sound when you turn the key or press start
• headlights that are dim at idle
• a battery or charging warning light
• a sulfur (rotten-egg) smell
• a swollen or bloated battery case
• needing jump-starts more often

AAA’s Mountain West Group adds corrosion on the terminals.

How can you make a battery last longer in the heat?

• Test it before summer. AAA recommends a test before summer and every year once the battery is 3 years old. Interstate Batteries suggests a test every spring and fall.
• Park in the shade or a garage when you can, as AAA suggests.
• Check the terminals and mounts. AAA suggests checking the terminals for corrosion and making sure the battery is mounted securely.
• Consider an AGM battery. AAA suggests absorbed glass mat (AGM) batteries for hot regions. Check that one is right for your vehicle.
• Drive a car that sits. Interstate Batteries suggests driving an idle car at least 30 minutes a week.
• Buy a fresh battery. Consumer Reports, citing AAA, suggests buying one less than six months old.

Should you jump-start, replace or tow?

Situation	What usually makes sense
Cranks slowly or clicks, battery case looks normal	A jump-start, then have the battery tested
You’ve needed jumps more than once lately	Have it tested and probably replaced
Battery case is cracked, leaking or swollen	Don’t jump it; replace the battery or tow the car
Won’t start even after a jump	A tow to a shop; the cause may be the starter, alternator or something else
Battery light comes on while driving	Get to a shop or call for help; the battery may not be charging
Hybrid or EV won’t power up	Follow the manual’s jump-start steps; if that fails, ask about a flatbed

A jump-start only gets the engine running. It does not fix a worn-out battery, so get it tested soon after. See jump-start service for what the call involves, and local towing in Lancaster if the car has to go to a shop.

What about hybrids and electric cars?

Most hybrids and EVs still carry a small low-voltage battery, usually 12 volts, that powers the computers, locks and lights and lets the car switch on. If it dies, the car may not power up at all, even with a charged main battery. Heat wears on it like any other 12-volt battery.

Jump-starting a hybrid or EV follows the owner’s manual. Some have dedicated jump points under the hood rather than direct access to the battery. Tell the dispatcher it is a hybrid or EV when you call. If the car can’t be powered up and has to be moved, many EVs need a flatbed; see towing AWD vehicles and EVs.

For a jump-start, a lockout or other help where the car is, see roadside assistance.