can you keep batteries in car

[SanReese]

Yes, you can keep batteries in a car, but it is generally not recommended for extended periods, especially in extreme temperatures. The main risks involve temperature extremes, which can significantly accelerate battery discharge and cause permanent damage. A car's interior can quickly become an oven in summer or a freezer in winter, both of which are detrimental to battery health and safety.

The ideal storage environment for most common batteries—like AA, AAA, or 9-volt batteries for key fobs or portable devices—is a cool, dry place. A car's glove box or center console offers minimal protection from temperature swings.

Primary Risks of Car Battery Storage:

Risk Factor	Effect on Batteries	Potential Consequences
High Heat (Summer)	Accelerates chemical reactions inside the battery, leading to rapid discharge. Alkaline batteries may leak corrosive potassium hydroxide. Lithium batteries can swell or, in rare cases, catch fire.	Leakage damaging the device, permanent capacity loss, and safety hazards.
Extreme Cold (Winter)	Slows chemical reactions, causing a temporary, significant voltage drop. While performance may return at room temperature, repeated freezing can cause internal damage.	Device failure when needed, reduced lifespan, and potential casing rupture.
Temperature Cycling	Constant expansion and contraction from daily temperature swings degrades internal components over time.	Shorter overall battery life and inconsistent performance.

For your car's main 12-volt lead-acid battery, the concern is different. If you aren't driving the car regularly, the battery will slowly discharge due to parasitic drain from systems like the clock or alarm. A completely discharged lead-acid battery can sulfate, ruining its ability to hold a charge. If you plan to store a vehicle for more than a few weeks, using a battery maintainer (trickle charger) is the best practice to keep the battery healthy.

In short, for short-term storage of small batteries, it's low-risk. For long-term storage or for your vehicle's own battery, taking it indoors or using a maintainer is the wiser choice to ensure reliability and safety.

[VonKathryn]

I learned this the hard way. I left a pack of AA batteries in my glove box over the summer for a flashlight. When I needed them, not only were they dead, but one had leaked all over the inside of my nice Maglite, ruining it. The heat just cooks them. Now, I only keep a spare set in the car during the cooler months, and I make a point to rotate them out. It’s not worth the gamble.

[IsabelleRose]

It's fine for a day or two, but I wouldn't make a habit of it. Think about how hot it gets inside a parked car on a sunny day. That heat speeds up the chemical process inside the battery, draining its charge much faster. For something you rely on in an emergency, like a flashlight, you want to know it's going to work. Storing batteries at room temperature is a simple way to guarantee they’ll be ready when you need them.

[Matilda]

From a safety standpoint, the primary concern with lithium-based batteries in hot cars is the potential for thermal runaway. While rare, a damaged or poorly manufactured lithium-ion battery can overheat and potentially ignite when subjected to high temperatures. For the common alkaline batteries, the bigger issue is leakage, which can destroy your devices. My advice is to treat batteries like any other electronic component: store them in a climate-controlled environment for maximum safety and longevity.

[FrankLee]

If you're talking about keeping a spare battery for your key fob in the car, that's a bit of a catch-22. If your fob battery dies and the spare is also in the hot car, it might be dead too. It's more reliable to keep a spare at home or in your office. For your car's actual 12-volt battery, the problem isn't storage but lack of use. If you don't drive regularly, the battery drains. A battery maintainer is a great investment to keep it topped up if the car sits for long periods.