What Could Happen If You Store Tool Batteries In A Hot Car Or Garage

No matter how much you want to stay organized and keep your power tools and accessories just on one wall of your garage, the reality is that they will still get stashed wherever it's most convenient for you. Maybe you want to be prepared for a roadside emergency, so you keep some tools and batteries in your car. Or perhaps you're always working on a home improvement project and store your equipment right by the garage window where the sun shines through.

While doing so might seem harmless at first, you're probably forgetting that your car and your garage window wouldn't stay cool all the time. At some point, they can get quite hot. Keeping your storage unit in a hot car or garage is one of the biggest mistakes you can make to ruin your power tool batteries. But just how bad can it get? What actually happens to a tool battery when it's exposed to too high of a temperature?

Electronics and heat usually don't mix, and your power tool batteries are no exception. That's why manufacturers recommend storing them in a location where ambient temperatures are only between 41°F and 77°F (5°C and 25°C). If you go over this safe range and most especially beyond 120°F (50°C), you risk damaging your tool battery.

One of the worst effects of prolonged heat exposure is permanent capacity loss. This means the battery can no longer store the same amount of charge as it did originally, effectively reducing the total runtime it can provide. According to Battery University, the educational site sponsored by Canadian battery manufacturer Cadex Electronics, a Li-ion battery stored at 40% is estimated to retain only 75% of its capacity after a year in storage at 140°F (60°C). This significantly drops to 60% after just three months if the battery was fully charged when it was stored.

Storing your tool batteries in a hot car or garage can degrade the components faster than usual, too. You wouldn't want to have a degraded battery — not only can it suffer from permanent damage that renders it unusable, but it can also cause an explosion and fire.

The safest way to store your Li-ion batteries is in a dry and cool place away from direct sunlight. Remove them from the back of your car or your hot garage, and place them somewhere with a room temperature. If you won't be using the battery for months, ensure it's kept at about 50% charge, rather than fully charged.