Quick answer
- Ensure the battery is warm enough to charge; per Milwaukee's verified charger manuals (48-59-1812 dual-bay and 58-22-1815 M18), the acceptable charging range is 40°F to 104-105°F (5°C to 40°C) — NOT the generic 32°F Li-ion floor. If the pack is below 40°F, warm it indoors before charging.
- Check for a defective battery by using a different charger or testing another battery in the same charger.
- Inspect the charger for faults; on Milwaukee M18/M12 chargers, a red blinking LED typically means the pack temperature is out of range, while red+green alternating indicates a defective pack.
- If the battery is swollen or damaged, do not attempt to charge it; recycle it properly.
Symptoms
When a Milwaukee battery won't charge, you may notice the following symptoms:
- LED Patterns: The charger LED may show a steady red light, indicating charging, or a blinking red light, suggesting the battery is too hot or cold. If the LED alternates between red and green, this indicates a defective battery pack.
- Sounds: You may hear no sound at all from the charger, or a faint clicking sound when the battery is inserted, which could indicate a fault.
- Behavior Under Load: If the battery is inserted into a tool and the tool fails to operate, this is a sign that the battery may not be holding a charge.
Quick checks
Before proceeding with deep troubleshooting, verify the following:
- Temperature: Ensure the battery is within Milwaukee's published charging range — 40°F to 104-105°F (5°C to 40°C) per the 48-59-1812 / 58-22-1815 manuals. Below 40°F the charger will display a temperature fault rather than charging. Warm the pack to room temperature before retrying.
- Charger Functionality: Test the charger with a different, known-good battery. If it charges the other battery, the issue may be with the original battery.
- Battery Condition: Inspect the battery for physical damage, such as swelling or corrosion. If any damage is noted, do not use the battery.
- Charger LED: Check the LED indicator on the charger. Refer to the specific model's LED fault patterns to identify potential issues.
- Connection: Ensure the battery contacts are clean and free of debris. Dirty contacts can prevent proper charging.
Step-by-step fix
- Remove the Battery: Always start by removing the battery from the tool to prevent any accidental activation.
- Inspect the Charger: Check the charger’s LED indicator. For example, the Milwaukee M18 charger shows a steady red light when charging and a green light when fully charged. If it’s blinking red, it may be too hot or cold.
- Warm the Battery: If the battery is cold, place it in a warm environment for at least 30 minutes. This allows the battery management system (BMS) to reset and may enable charging.
- Test with Another Charger: If available, try charging the battery with a different Milwaukee M18 charger. If it charges, the original charger may be defective.
- Check Battery Contacts: Clean the battery contacts with a dry cloth to ensure a good connection. Corroded contacts can prevent charging.
- Replace the Battery: If the battery still won’t charge and shows signs of damage (swelling, corrosion), it’s best to replace it. Consider upgrading to a Milwaukee M18 REDLITHIUM XC 5.0Ah Battery (48-11-1850) for improved performance.
View Milwaukee M18 REDLITHIUM XC 5.0Ah Battery (48-11-1850) on Amazon (paid link)
View Milwaukee M18 REDLITHIUM XC 5.0Ah Battery (48-11-1850) on Home Depot (paid link)
If it still isn't working
If the battery still does not charge after following these steps, consider the following escalation options:
- Warranty Service: Check if your battery is still under warranty. Milwaukee offers a 3-year warranty on M18 batteries. Contact Milwaukee customer service for warranty claims.
- Service Center: If the battery is out of warranty, take it to an authorized Milwaukee service center for further diagnosis and potential repair.
- Replacement: If the battery is confirmed defective and not under warranty, purchasing a new battery may be the best option.
FAQ
Why won't my Milwaukee battery charge?
There could be several reasons: the battery may be too cold, the charger may be defective, or the battery itself may be damaged.
What does it mean if the charger is blinking red?
A blinking red light typically indicates that the battery is too hot or cold for charging. If it continues to blink after warming the battery, it may indicate a fault.
Can I use a different brand charger for my Milwaukee battery?
No, using a charger from a different brand can damage the battery and void any warranty. Always use Milwaukee chargers with Milwaukee batteries.
How can I tell if my battery is defective?
Look for physical signs of damage, such as swelling or corrosion, and test the battery in a different charger. If it still doesn’t charge, it’s likely defective.
What should I do with a damaged battery?
Do not attempt to use or charge a damaged battery. Recycle it properly at designated drop-off locations like Home Depot or Lowe's.