Quick answer
- A blinking red and green LED on your Milwaukee battery charger indicates a defective battery pack.
- Ensure the battery is within Milwaukee's published charging temperature range — 40°F to 105°F (5°C to 40°C) per the 48-59-1812 manual. Below 40°F the charger will display a temperature fault, not charge.
- Check that you are using the correct charger for your battery model.
- If the battery is swollen, punctured, or corroded, do not attempt to charge it; recycle it properly.
Symptoms
When your Milwaukee battery won't charge, you'll typically observe the following:
- The LED on the charger blinks red and green alternately, indicating a fault with the battery pack.
- You may hear no sounds from the charger, as it is unable to initiate charging.
- Under load, the tool may not operate at all or may shut down unexpectedly, confirming that the battery is not providing power.
Quick checks
Before diving into deeper troubleshooting, verify these key points:
- Temperature Check: Ensure the battery is within Milwaukee's published charging range, 40°F to 105°F (5°C to 40°C). If the pack is below 40°F, allow it to warm to room temperature indoors before attempting to charge.
- Charger Compatibility: Confirm you are using a Milwaukee M18 charger, such as the Milwaukee 48-59-1812. M12 chargers will not charge M18 batteries.
- Battery Condition: Inspect the battery for any visible damage, such as swelling or corrosion. Damaged batteries should not be used.
- Charger Functionality: Test the charger with another known-good battery to ensure it is functioning properly.
- Connection Check: Ensure the battery is seated correctly in the charger and that there is no debris obstructing the connection points.
Step-by-step fix
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Remove the Battery: Always start by removing the battery from the charger to ensure safety before performing any checks or repairs.
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Inspect the Battery: Look for physical damage. If the battery is swollen or has any punctures, it should be recycled immediately. Do not attempt to charge a damaged battery.
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Check Temperature: If the battery feels warm, allow it to cool for at least 30 minutes before attempting to charge. If it’s cold, let it reach room temperature.
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Test the Charger: Use a different battery (if available) to test the charger. If the charger works with another battery, the issue is likely with the original battery.
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Charge Again: Reinsert the battery into the charger and observe the LED indicator. If it still blinks red and green, the battery is likely defective.
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Consider Replacement: If the battery is confirmed defective, consider replacing it with a new 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 continues to show a blinking red and green LED after following the above steps, consider the following escalation options:
- Warranty Claim: Check if the battery is still under warranty. Milwaukee offers a 3-year warranty on M18 batteries. Contact Milwaukee customer service for assistance.
- Service Center: If the warranty is expired, take the battery and charger to an authorized Milwaukee service center for diagnosis.
- Replacement: If the battery is beyond repair, purchasing a new battery may be the most efficient solution.
FAQ
Why is my Milwaukee battery blinking red and green?
This LED pattern indicates that the battery is defective and cannot be charged. It is essential to inspect the battery for any physical damage.
Can I charge my battery if it’s cold?
No, lithium-ion batteries will not charge below approximately 32°F (0°C). Allow the battery to warm up to room temperature before charging.
What should I do if my charger is not working?
Test the charger with a different battery to confirm its functionality. If it works with another battery, the issue lies with the original battery.
How do I recycle a damaged battery?
Recycled batteries can often be taken to retailers like Home Depot or Lowe's, or you can find a Call2Recycle drop-off location near you.
What if my battery is swollen?
A swollen battery is a sign of failure and should not be used. It should be recycled immediately to prevent potential hazards.