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Recharge a lithium battery with the original charger or an approved replacement, at room temperature, and unplug it when full.
For the full breakdown, see our best Rechargeable Lithium Batteries guide.
Most of us never think about how to recharge lithium batteries until the day a charger feels too hot to hold. Charging is the stage when lithium-ion batteries fail most often: a wrong charger, a soft surface, or an overlong charge can turn a normal cell into a fire hazard. The safe routine, though, is short and easy to learn.
Three habits handle nearly every situation: use the charger specified for the device, charge where you can watch it, and unplug when full. High-energy machines like e-bikes and e-scooters add one more rule — charge outside. The rest of this article walks through each step and names the mistakes worth avoiding.
Start With The Charger The Manufacturer Approved
The manufacturer’s instructions define both the voltage and current the battery expects and the charging method it was designed for. A charger that mismatches those numbers can overcharge, undercharge, or overheat the pack, and overheating is what turns lithium-ion problems into fire risks. When the original charger breaks or gets lost, replace it with one approved for that exact device — not a universal adapter that happens to fit the plug. Safety guidance also recommends UL-listed or nationally recognized testing lab products for battery-powered gear.
Damaged cells are a different problem entirely. Never charge a battery that is swollen, leaking, hot, or giving off an odd smell, and stop the moment one starts doing any of that mid-charge. Popping, discoloration, and excessive heat are all immediate stop signs.
When a battery no longer holds a useful charge, don’t keep forcing it. Our roundup of the best rechargeable lithium batteries compares dependable replacements by size and typical use.
Charging A Lithium Battery: The Step Order That Works
The routine below follows manufacturer instructions and NFPA’s guidance on lithium-ion battery safety, which identifies charging as the riskiest period in a lithium battery’s life. Follow it in order, every time.
- Read the manufacturer’s charging instructions. The device’s user manual and charging rules come
