Milwaukee Charger Flashing Red And Green – What Does It Mean?

Milwaukee Charger Flashing Red And Green

Milwaukee is a popular brand, with many people using their power tools. The blinking LED lights can be confusing when using your first Milwaukee charger. Understanding what flashing lights mean will help you identify when there is a problem.

Key Takeaways: 

  • A solid red light indicates the battery is charging.
  • If the battery charge indicator stays green for an extended period, it is fully charged.
  • Flashing green and red lights show the battery isn’t charging and could be due to temperatures being too high/low, a faulty charger or battery, or poor connection.
  • The battery can shut down to protect your equipment. You’ll reset it by placing it on the charger.
  • To reset the Charger’s PCB circuitry, disconnect it from its 120VAC power source and remove the battery pack.

Why Is My Battery Tender Blinking Red and Green?

A battery tender flashing red and green means;

  • The battery is in maintenance mode after reaching the 72-hour safety timer
  • The battery is defective

72-Hour Safety Timer

The Milwaukee battery tender tries to reach a target voltage of 14.75. It automatically switches to maintenance mode if it doesn’t reach the target within 72 hours. You’ll see it blinking red and green, especially when charging a large car battery.

While the red and green lights imply that your large battery is yet to reach its maximum charge capacity, test your battery to ensure it’s in good working condition.

For a standard battery, the tender flashing red and green implies an issue with the connection. A connection issue arises due to resistance in the connection or improper wiring. You could have an expert work on the battery to fix it.

Defective Battery

Sometimes the red and green flashing lights mean there’s a faulty battery. A defective battery may result from the following: 

  • A corroded battery terminal
  • Sulfated battery

You can use a vinegar solution to clean corroded terminals. A slow charge can help reverse sulfated batteries. The other option is to replace the defective battery. 

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What Does It Mean When Milwaukee Battery Flashes?

Your Milwaukee charger communicates to you by flashing red and green lights. The red and green flashes indicate the following:

  • Temperature
  • A faulty battery
  • Poor connection
  • Charging status


A charger will flash a red light when the battery’s temperature is too low or too high. You don’t have to use a thermostat to know the temperature. You can feel it with your hand. 

The charging process makes the battery warm, but the charger will alert you when it gets warmer than usual. Disconnect the battery immediately because continued charging can damage it. Some chargers may stop charging the battery.

Faulty Battery

When you insert a faulty battery and attempt to charge it, the charger flashes red and green lights. Remove the battery, clean the terminals, then plug it back in. If it still doesn’t charge, you must fix the battery or replace it before connecting the charger again.


Poor Connection 

Flashing charger lights may indicate a poor connection between the charger and the battery. Push the battery firmly into the slot to ensure it connects well. If the flashing doesn’t stop, check if the charger or battery is faulty. You can connect the battery to another charger to see if it charges. 

Charging Status

A Milwaukee charger shows a solid red light when charging. The solid green LED light means that the battery is fully charged. When you see flashing lights, it indicates that the battery isn’t charging. 

How Do You Reset a Milwaukee Battery Charger?

Sometimes the battery pack can shut down due to high temperatures or short-circuiting. It shuts down to protect your equipment. You might think the batter is dead, but it only needs a reset.

You can reset the battery by placing it on the charger. Press the fuel gauge button to know if the battery needs a reset. The bottom gauge will flash once, indicating you must reset the battery. 

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How Do I Know if My Milwaukee Battery Is Bad?

You may determine that your Milwaukee battery is bad if:

  • It doesn’t charge: Ensure your battery is at room temperature before charging it. If it doesn’t charge completely, contact Milwaukee customer support.
  • A dead battery: Instead of replacing it immediately, consider jump-starting it. To jump-start: 
    • Place a 9-volt battery on your dead battery’s leads. 
    • Wait for 30 seconds (remember, the single lead represents positive while the double lead is negative).
    • Connect the charger to the battery. It should charge.
  • The battery drains power quickly: Batteries wear out over time, but if you notice that your battery dies out a lot sooner, it is a sign that the battery is bad. You can contact customer support.

Milwaukee Charger Flashing Red and Green Without Battery in It

When your charger flashes without a battery, unplug it from the socket and wait for the flashing to stop. You can then connect the battery, then plug it back in. It will charge normally. 

Milwaukee M12 M18 Charger Flashing Red and Green

When the Milwaukee M12 or M18 charger flashes red and green lights, it may mean two things;

  • A faulty battery
  • Poor connection

Check the issue before contacting customer support. 

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Milwaukee Solid Red Light

A solid red light on the Milwaukee charger indicates that the battery is charging. Depending on the battery size, it will stay for a few hours before shifting to a solid green to indicate a fully charged battery. 

Milwaukee Charger Blinking Red

A fast flashing red light indicates that the battery isn’t charging because it’s too hot or cold. Once the battery attains the correct charging temperature, charging will begin. It is advisable to disconnect the battery and charge it at room temperature.

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