Battery Gets Hot? Troubleshooter
Warm is normal. Too hot to hold isn't.
Lithium packs warm up under heavy use. Watch for signs of damage. Work through one question at a time. You can go back or start over whenever you like.
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Safety: this troubleshooter is general information. Follow your battery and tool maker's instructions. Don't open a pack or a mains-powered charger, bypass a protection board or force-charge a rejected pack.