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Whether you’re shopping for a new power tool to add to your collection or a handy utility knife to keep in your pocket, Milwaukee is one of the most reliable brands to consider. It ranks highly among other major power tool brands, thanks to durable construction and Milwaukee’s proprietary M18 Fuel battery system.

The M18 Fuel system utilizes 18-volt batteries that are compatible with Milwaukee’s full M18 product range. The M18 Redlithium Forge HD12.0 batteries Milwaukee launched in June 2024 offer a 50% boost to power and lifespan over its predecessor, giving cordless M18 tools a strong edge against their competitors.

While Milwaukee’s M18 Redlithium batteries generally offer more positive features than negative ones, they’re not immune to some of the most common problems affecting power tool batteries. These 18-volt batteries, along with other batteries manufactured by Milwaukee, are prone to small issues like not fully charging, huge concerns like overheating, and more. Here are the most common problems you may encounter with Milwaukee batteries, along with a few solutions that could help you fix or reverse the issue.

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Like many other power tool batteries, it’s possible that a Milwaukee battery could encounter issues with charging. Of course, if you encounter this problem with a new battery, it’s possible that it could be defective, and you should contact Milwaukee to potentially receive a free battery replacement. However, if your battery suddenly starts giving you trouble after years of no issues and refuses to charge, as this customer on a Practical Machinist forum experienced, that’s more concerning.

This particular customer notes connecting the battery to its charger and seeing the indicator light go from red to green. Yet, it only ends up with enough power to turn on a tool’s built-in light, but not actually run the tool itself. Responses on this forum, as well as on a Redditor’s post with a similar issue, suggest that it may be a dead cell within the battery, and that jumping the battery could potentially resolve the issue. Jump-starting the battery can also work as a solution for a battery that refuses to charge at all, an issue another Reddit user encountered.

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Some Milwaukee customers report issues with their battery not completely charging, even after sitting on the charger for hours. While this is at least a better issue to have than a battery refusing to charge at all, it’s still not ideal.

On a Tools in Action forum post, one customer complains that two of their M18 batteries appear to be fully topped up, with a green indicator light on the charger, but when they check each battery’s charge level after removing it from the charger, it only shows two bars worth. In this case, many comments suggest the customer’s issue probably lies with the charger, rather than the batteries themselves. People recommend checking to see if the charger is under warranty, and if not, investing in a new charger.

Similarly, another customer requesting help on Just Answer had an M18 Redlithium battery that would only show three out of five LED charge indicators after charging. Unlike the first customer, this customer had three other M18 batteries that worked perfectly with the charger, effectively eliminating the charger as the issue. The main response to this customer’s problem includes multiple possible causes and corresponding fixes for each cause, including cell imbalance, circuit issue, overheat protection, and a sleeping battery.

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An overheating Milwaukee battery is a pretty common problem reported among users, but in most cases, it’s easily fixable. One Redditor reported that their M18 battery overheated in a chainsaw after less than 20 minutes of use. Then, another Reddit user had the same issue with two M18 batteries and their chainsaw.

Between the comment threads on both posts, the battery is likely underpowered for the task at hand. It’s working too hard and too fast, causing the battery to overheat and shut down, even though there’s still charge to work with. A few responses recommend buying a more powerful battery and taking regular breaks.

Of course, sometimes an overheating battery issue can escalate to a problem involving fire or possibly explosions. In one of the biggest power tool recalls in U.S. history, about 1 million Milwaukee Power Plus, Chicago Pneumatic, and Extractor 14.4- and 18-volt battery packs were recalled due to a risk of exploding if a vent on the battery cell was accidentally damaged during use. The fix for these recalled batteries was to replace them entirely. If you spot one of these used batteries being sold online, steer clear of it.

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It’s natural for a battery to lose capacity over time and struggle to stay charged for as long as it did when it was brand new. However, if a power tool keeps dying abnormally fast, that may signal a larger issue at hand.

One Reddit user outlines a problem with their new impact driver, noting that its M18 battery dies after only driving 100 screws. Previously, this Redditor was using a 10-year-old Mastercraft drill with a 14-volt battery, and they report it lasting much longer than the new M18 impact driver, which only seems to last about 30 minutes before needing to be charged again. Most of the replies in this thread sum up the issue as a bad battery and advise the original poster to reach out to customer service for a new battery or buy a larger battery.

Another Redditor’s Milwaukee battery was draining quickly because it wasn’t actually charging when placed on the charger. Comments suggest that it may be failing to charge because the battery is faulty, has a dead cell, or needs to be balanced. Alternatively, if your troublesome battery is relatively new, it’s worth reaching out to Milwaukee to see if it can be replaced under warranty at no cost.

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A power tool battery, unfortunately, won’t last forever. Depending on the frequency of regular use, a typical battery will last between 2 and 5 years before needing to be replaced. If you find that you’re entirely replacing your Milwaukee batteries more often than that, like this Reddit user, something might be up.

According to many Redditors in the comment thread of the post mentioned above, these Milwaukee batteries may be dying so quickly due to poor cell quality, high power-draining tools, or slow balancing technology. The original poster and multiple comments describe having 4.0 Ah and 5.0 Ah batteries from nearly 10 years ago that still function perfectly, and a fresh 9.0 Ah battery that ends up lasting less than the older batteries after a couple of years of regular use.

The OP even goes on to say that they suspect the company could be knowingly selling batteries with defective cells, but this claim hasn’t been confirmed in any way. Examining the history of Milwaukee Tools and power tools in general, older tools are often regarded as higher quality and more reliable than modern tools, which some people believe is either a cost-saving measure or further evidence of planned obsolescence. Either of these reasons could explain why Milwaukee batteries need to be replaced so often, or it could be that whatever job the power tool is taking on is demanding too much from the battery.

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To compile this list of common problems ailing Milwaukee power tool batteries, we started with first-hand knowledge of battery issues in general. Smartphones, laptops, and other battery-powered devices, just like power tool batteries, are prone to overheating, losing capacity over time, and charging issues.

From there, we poured through Reddit and other forums to find anecdotal customer experiences with Milwaukee batteries. Often, when we’d stumble across an issue from one customer, there were multiple other customer experiences to back up the first claim. We also checked the Consumer Product Safety Commission (CPSC) database for any major battery-related recalls from Milwaukee.