Milwaukee M18 Battery Not Charging: How to Fix?

Milwaukee M18 Battery Not Charging: How to Fix?

As technology continues to advance at a rapid pace, more and more devices are becoming wireless and battery-powered. This has been especially true in the power tool industry, with cordless tools becoming increasingly popular among both professionals and DIY enthusiasts.

One of the most well-known manufacturers of cordless power tools is Milwaukee, whose M18 battery line offers high performance and long-lasting power for a variety of tools. However, like any other battery-powered device, there may come a time when you encounter issues with your Milwaukee M18 battery not charging.

In this guide, we will take a look at some common reasons for a Milwaukee M18 battery not charging and provide solutions on how to fix the problem.

What Is Milwaukee M18 Battery?

Before we dive into troubleshooting tips, let’s first understand what a Milwaukee M18 battery is. The M18 battery line is a proprietary high-performance rechargeable lithium-ion battery system developed by Milwaukee Electric Tool Corporation.

This battery line is designed to power various Milwaukee cordless tools, including drills, saws, impact drivers, and more. It offers longer run-time, higher power output, and better durability compared to traditional nickel-cadmium batteries. [4]

What Is Milwaukee M18 Battery?

Reasons Why The Milwaukee M18 Battery Won’t Charge

There are several reasons why your Milwaukee M18 battery may not be charging properly. Here are some of the most common ones:

A bad cell refers to one or more individual cells within the battery pack that have failed. A single bad cell can prevent the entire battery from charging, resulting in a dead battery. This can happen due to overcharging, overheating, or simply wear and tear over time.

Another common reason for a Milwaukee M18 battery not charging is a faulty charger. If the charger is not functioning properly, it may not deliver the correct amount of voltage to charge the battery. This can happen due to damaged cords or internal issues with the charger itself.

In some cases, dust and debris can build up in the battery or charger, causing them to malfunction. This is a common issue with tools that are used in dusty or dirty environments. [4]

Makita m18 Battery Terminals

First Terminal: Positive (+)

The positive terminal is the larger of the two and is typically marked with a plus sign or the letters “Pos.” This terminal provides power to the tool when it is turned on. [4]

Second Terminal: Negative (-)

The negative terminal is smaller and is usually marked with a minus sign or the letters “Neg.” This terminal completes the circuit and allows current to flow through the tool. [4]

Three Hidden Terminals

In addition to the two main terminals, there are also three hidden terminals located on the bottom of the battery pack. These are used for communication between the battery and the tool, such as monitoring charge levels and temperature. [4]

Fifth Terminal: The Thermistor

The fifth terminal is a small sensor that monitors the temperature of the battery. If the battery gets too hot, it will prevent charging to avoid damage. [4]

Makita m18 Battery Terminals

How To Charge A Milwaukee M18 Battery?

To properly charge your Milwaukee M18 battery and ensure optimal performance, follow these simple steps:

  1. First, ensure that the charger is securely plugged in and turned on for a reliable power source.
  2. Gently insert the battery pack into the charger, making sure that the terminals are correctly aligned and facing downward.
  3. Once the battery is properly inserted, the charging light will illuminate, serving as an indicator that the charging process has begun.
  4. During the charging process, it’s important to note that the light will remain on until the battery reaches a full charge. At this point, the light may either turn off completely or change color, indicating that the battery is fully charged and ready for use.
  5. Once the battery has reached a full charge, carefully remove it from the charger and store it in a safe place until needed for your next project or task. [1]

By following these detailed steps, you can ensure that your Milwaukee M18 battery receives the proper care and attention it needs to provide reliable and long-lasting power for your various applications.

Check The Charger With A Multimeter First

If you suspect that the charger is the cause of your Milwaukee M18 battery not charging, you can use a multimeter to test its voltage output. Here’s how:

  1. Set your multimeter to DC Voltage mode.
  2. Touch the red and black probes to the positive (+) and negative (-) terminals on the charger, respectively.
  3. The reading should match the voltage listed on the charger (usually 18V or 20V). If it is significantly lower or higher, this indicates an issue with the charger.

If your multimeter reading does not match the voltage listed on the charger, you may need to replace the charger. However, if it matches and your battery still won’t charge, then there may be an issue with the battery itself. [1]

Clean Off The Terminals

If you’re facing issues with your Milwaukee M18 battery not charging, here’s a simple troubleshooting tip that could help. Over time, it’s common for dirt and debris to accumulate on the terminals of both the battery and charger, which can hinder the charging process by preventing proper contact. To address this, take a soft cloth or a small brush and gently wipe away any dirt or debris from the terminals. By doing so, you’ll ensure that the terminals make proper contact, allowing for a smooth and efficient charging process. Taking a few moments to clean the terminals can potentially resolve the issue and get your battery charging again in no time. [1]

Check That There Is Power To The Charger

If your Milwaukee M18 battery is not charging, it’s also worth checking if there is power to the charger. This can be easily done by plugging in another device or tool to the same outlet and seeing if it powers on.

If there is no power to the charger, then you may need to check your circuit breaker or try a different outlet. Sometimes, circuit breakers can trip or outlets can become faulty, so troubleshooting these possibilities can help pinpoint the issue.

On the other hand, if power is present and the charger still doesn’t work, there may be an underlying problem with the charger itself. It could be a faulty connection, a damaged component, or a malfunctioning circuitry. In such cases, it is recommended to reach out to the manufacturer or an authorized service center to have the charger inspected and potentially replaced. Remember, ensuring a fully functional charger is crucial to keeping your Milwaukee M18 battery operating at its best. [1]

Check That There Is Power To The Charger

Hold The Power Button

If you’ve tried all the troubleshooting tips above and your Milwaukee M18 battery is still not charging, here’s one last thing you can do before contacting customer support. Hold down the power button on your tool while inserting the battery into the charger. This will reset the communication between the battery and charger, which may have been disrupted due to an error or malfunction.

If this method does not work, then it’s time to reach out to the manufacturer for further assistance. They may be able to provide additional troubleshooting steps or determine if your battery or charger needs to be replaced. With proper care and maintenance, your Milwaukee M18 battery should provide reliable power for all your projects and tasks. [3]

Troubleshoot Your Cable, Charger, Outlet & Case

If none of the above methods have resolved your issue and your Milwaukee M18 battery is still not charging, it’s time to delve deeper into potential causes. First, check your charging cable for any damage or frayed wires that could be preventing proper power flow. Next, inspect the charger itself for any visible damage or defects. If both the cable and charger appear to be in good condition, then consider trying a different outlet to eliminate the possibility of a faulty power source. Lastly, if you have a protective case on your battery, remove it and try charging without it as sometimes these cases can interfere with the charging process. [3]

Troubleshoot Your Battery Charge Status

If your Milwaukee M18 battery is still not charging after all the previous steps, it’s possible that there may be an issue with the battery’s charge status. To troubleshoot this, try using a different tool or device to insert the battery and see if it charges. If it does, then there may be an issue with the original tool you were trying to use. If it still doesn’t charge, then the battery may be completely drained or damaged and in need of replacement. [3]

Troubleshoot Your Screen Display

In some cases, the issue may not be with your battery or charger, but rather with the display screen on your tool. If you have a digital display screen that shows the battery’s charge level, try turning off your tool and removing and reinserting the battery. If the display still shows zero charge, then there may be an issue with the screen itself. In this case, it’s best to reach out to the manufacturer for assistance. They may be able to provide troubleshooting steps or arrange for a repair or replacement of your tool. [3]

Consider Replacing The Battery

If all else fails and your Milwaukee M18 battery is still not charging, it may be time to consider replacing the battery altogether. Over time, batteries can degrade and lose their ability to hold a charge, especially if they are used frequently or stored improperly. If you’ve had your battery for a significant amount of time and have exhausted all troubleshooting options, it’s likely that the battery has reached the end of its lifespan and needs to be replaced. Contact the manufacturer or an authorized dealer for a replacement battery that will provide reliable power for your tools and projects. Overall, keeping your charging equipment clean and well-maintained, checking for power supply issues, resetting communication between the battery and charger, troubleshooting potential causes, and considering replacement options are all important steps in fixing a Milwaukee M18 battery that is not charging. By following these tips and seeking assistance from the manufacturer when needed, you can keep your tools powered up and ready to tackle any job. [2]

Consider Replacing The Battery

Advantages Of Milwaukee M18 Battery System

The Milwaukee M18 battery system is known for its high-quality and reliable performance, making it a popular choice among professionals and DIY enthusiasts. Here are some of the advantages that make this battery system stand out:

  • Versatility: The M18 battery system offers a wide range of tools and equipment that can be powered by the same battery, eliminating the need to switch or carry multiple battery types.
  • Longer run time: With advanced technology and larger capacity options, the M18 battery system provides longer run time for your tools, reducing the need to stop and recharge frequently.
  • Fast charging: The M18 battery charges quickly, allowing you to get back to work in no time.
  • Durability: Made with high-quality materials and designed to withstand tough job site conditions, the M18 battery is built to last.
  • Compatibility: The M18 battery system is compatible with all Milwaukee 18-volt tools, giving you the flexibility to expand your collection without having to purchase additional batteries. [2]

Disadvantages Of Milwaukee M18 Battery System

While the Milwaukee M18 battery system offers many advantages, there are a few potential downsides to consider:

  • Cost: The initial cost of purchasing the M18 battery and charger may be higher compared to other battery systems, but it is a long-term investment that can save you money in the long run.
  • Compatibility limitations: While the M18 battery is compatible with all Milwaukee 18-volt tools, it may not be compatible with other brands, limiting your options if you have a mix of tool brands.
  • Limited selection: While the M18 battery system offers a wide variety of tools and equipment, there may be some niche or specialized tools that are not available in this battery platform.
  • Weight: The M18 battery is slightly heavier than other battery types, which may be a consideration for those who use their tools frequently or for long periods of time. [2]

Despite these potential drawbacks, the Milwaukee M18 battery system remains a top choice for many professionals and DIY enthusiasts due to its reliability, performance, and versatility.

Safety Precautionary Measures

When dealing with batteries, it’s important to take necessary safety precautions to avoid any potential hazards. Here are some general safety tips to keep in mind when using your Milwaukee M18 battery:

    • Always use the appropriate charger designed for your specific battery model.
    • Avoid storing or charging batteries in extreme temperatures (hot or cold).
    • Keep batteries away from water or other liquids.
    • Do not puncture, disassemble, or attempt to repair a damaged battery.
    • Use protective gear such as gloves and safety glasses when handling batteries.
    • If the battery shows any signs of swelling, overheating, or damage, stop using it immediately and seek assistance from the manufacturer. [2]

Safety Precautionary Measures


How do I know if my MILWAUKEE battery is bad?

There are a few signs that may indicate a bad Milwaukee M18 battery. If the battery does not hold a charge or takes a significantly longer time to charge than usual, it may be an indication of a faulty battery. Additionally, if the battery is visibly damaged or swollen, it should not be used and should be replaced.

Can MILWAUKEE batteries be repaired?

In most cases, Milwaukee M18 batteries cannot be repaired. If the battery is under warranty and shows signs of damage or malfunction, it can usually be replaced by the manufacturer. Attempting to repair a battery yourself may also void any existing warranty.

How do you reset a lithium-ion battery?

If your Milwaukee M18 battery is showing signs of not charging, you can try resetting it by unplugging the charger from the power source and then plugging it back in. This will reset the communication between the battery and charger. If this does not work, refer to the manufacturer’s instructions for further troubleshooting steps.

What to do with Milwaukee batteries that don’t work?

If your Milwaukee M18 battery is not working, try troubleshooting the issue by following some of the tips mentioned in this document. If all troubleshooting methods have been exhausted and the battery still does not work, it may need to be replaced. Contact the manufacturer for further assistance or to inquire about warranty options.

Do Milwaukee batteries go bad?

All batteries have a limited lifespan and will eventually need to be replaced. However, with proper care and maintenance, Milwaukee M18 batteries can last for several years before needing to be replaced. It’s important to follow the manufacturer’s instructions for charging and storing the battery to ensure its longevity.

Do Milwaukee batteries have lifetime warranty?

Milwaukee offers a 3-year warranty on M18 batteries. However, some models may have a longer or shorter warranty period, so it’s important to check the specific model’s warranty information before purchasing. Additionally, certain factors such as misuse or damage may void the warranty. Refer to the manufacturer’s website for more details.

Useful Video: Milwaukee M18 Battery one flashing light won’t charge


In conclusion, the Milwaukee M18 battery system is a top choice for professionals and DIY enthusiasts due to its reliable performance, wide selection of tools and equipment, and compatibility with all 18-volt Milwaukee tools. While there may be some potential drawbacks to consider, taking proper safety precautions and following the manufacturer’s instructions can help ensure the longevity of your batteries. If you encounter any issues with your Milwaukee M18 battery, refer to the FAQ section or contact the manufacturer for assistance. With proper care, these batteries can last for several years, providing you with reliable power and convenience for all your tool needs. So, don’t hesitate to invest in the Milwaukee M18 battery system and enjoy the benefits it has to offer!