Quick answer
- If your Milwaukee battery is flashing red and green, it indicates a defective battery pack.
- Before troubleshooting, ensure the battery and charger are both at a safe operating temperature (above 32°F).
- Check that you are using the correct charger for your battery model — M12 chargers do not charge M18 batteries.
- If the battery is still under warranty, consider reaching out for a replacement.
Symptoms
When your Milwaukee battery is not charging, you may observe the following symptoms:
- The LED indicator on the charger shows a red and green alternating light pattern, which indicates a defective battery pack.
- The charger may emit no sound or a faint clicking noise, suggesting it's attempting to engage the battery but fails.
- Under load, the tool may exhibit erratic behavior, such as shutting off unexpectedly or failing to start altogether.
Quick checks
Before diving into deeper troubleshooting, perform these quick checks:
- Temperature Check: Ensure the battery is above 32°F (0°C). Lithium-ion batteries will not charge if they are too cold due to the Battery Management System (BMS) safety interlock.
- Charger Compatibility: Verify that you are using the appropriate charger for your battery model. For example, the Milwaukee M12 charger will not charge M18 batteries.
- Battery Connection: Remove the battery and check for any debris or corrosion on the terminals. Clean them with a dry cloth if necessary.
- Charger Functionality: Test the charger with a different battery to confirm it is functioning properly. If the charger works with another battery, the issue likely lies with the original battery.
- Battery Age: Consider the age of the battery. If it is an older pack, it may have reached the end of its life cycle.
Step-by-step fix
- Remove the Battery: Always start by removing the battery from the tool to ensure safety during troubleshooting.
- Inspect the Battery: Look for physical damage, such as swelling or corrosion. If any damage is found, do not attempt to charge the battery.
- Warm the Battery: If the battery is cold, place it in a warm environment for at least 30 minutes to allow it to reach a safe operating temperature.
- Test the Charger: Use a different Milwaukee charger (e.g., Milwaukee 48-59-1812 for M18) to see if the issue persists. If the battery charges, your original charger may be faulty.
- Charge the Battery: Insert the battery into the charger and monitor the LED indicators. If the red and green lights continue to flash, the battery is likely defective.
- Consider Replacement: If the battery fails to charge after these steps, it may be time to replace it. Consider the Milwaukee M18 REDLITHIUM XC 5.0Ah Battery (48-11-1850) for optimal 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 is still not charging after following the above steps, consider the following options:
- Warranty Claim: If the battery is still under warranty, contact Milwaukee's customer service for a replacement.
- Service Center: Visit an authorized Milwaukee service center for professional diagnostics and repair.
- Replacement: If the battery is out of warranty and cannot be repaired, consider purchasing a new battery.
FAQ
Why is my Milwaukee battery flashing red and green?
This LED pattern indicates a defective battery pack. It may be due to internal failure or damage.
Can I use an M12 charger for my M18 battery?
No, M12 chargers are not compatible with M18 batteries. Always use the appropriate charger for your battery model.
What should I do if my battery is cold?
Warm the battery to at least 32°F (0°C) before attempting to charge it. Cold batteries will not charge due to the BMS safety interlock.
How can I tell if my charger is working?
Test the charger with a different battery. If it charges another battery successfully, the charger is likely functioning correctly.
What is the warranty on Milwaukee batteries?
Milwaukee offers a 3-year warranty on M12 and M18 batteries. If your battery is within this period, you may be eligible for a replacement.