Cordless trimmer battery won't charge

Symptoms

• Charger light doesn't turn on when battery is inserted
• Charging light blinks an error pattern
• Battery charges but drains almost immediately
• Battery feels warm without charging

Likely causes

• CommonDirty or corroded battery contactsDirt or oxidation on the metal contacts prevents a good electrical connection.
• CommonFaulty charger or cordA damaged charger cable or internal fault stops power from reaching the battery.
• PossibleBattery past its useful lifeLithium-ion batteries lose capacity and can fail to hold charge after a few hundred cycles.
• PossibleBattery too hot or cold to charge safelyMost chargers won't charge a battery outside a safe temperature range.
• Less commonFailed battery management circuitInternal protection circuitry can fail and block charging entirely.

What to do

1. Unplug the charger and inspect both the battery and charger contacts for dirt, corrosion, or debris.
2. Clean contacts gently with a dry cloth or a pencil eraser if oxidized.
3. Let the battery reach room temperature if it was very hot or cold, then try charging again.
4. Test the battery in the tool directly if possible, and test the charger with a different compatible battery to isolate which part is at fault.
5. Check the charger cord for visible damage or looseness at the connector.
6. If the charger works with another battery, the original battery has likely failed and needs replacing.
7. If no charger or battery combination works, the charging port on the tool itself may need inspection.

Tools and parts

• Dry cloth
• Pencil eraser (for contact cleaning)

When to call a pro

If a battery is swollen, extremely hot, or won't hold any charge after testing, take it to a battery recycling center rather than continuing to use or charge it.

Safety