Milwaukee M12 5.0 High Output Vs. 6.0: Which Battery Should You Get? (According To Reviews)

Nearly every major power tool brand has an large selection of battery packs to go with its products. Some even have multiple battery systems intended for different use cases. For example, Milwaukee has the M12, M18, and MX Fuel systems of power tools and corresponding batteries. Within each of those systems are multiple battery packs of varying size and capacity, enough to make anyone at least a little confused about what they actually need.

Within Milwaukee's M12 12-volt system are two battery packs designed for use in power tools: the M12 Redlithium 5.0 amp-hour High Output battery and the M12 Redlithium 6.0 battery. These battery packs seem the same at a casual glance, and they'll both run you the same $119.00 at your local Home Depot. Logic dictates that the 6.0 is the better battery — since it's newer and has a slightly higher capacity — but according to user reviews, that may not necessarily be the case. The user reviews for the M12 Redlithium 6.0 battery on the Milwaukee website are skewed heavily negative. More than two out of three users gave it a single star out of five, and it has an average rating of under two stars. The M12 5.0 XC high-output battery has a stellar 4.7 average rating, with almost 90% of reviewers giving it a perfect score.

According to Milwaukee, the M12 5.0 High Output battery delivers 25% more power and runtime than other batteries in the M12 system, as well as 25% cooler operation. It also claims that the M12 6.0 battery delivers up to three times the runtime of other M12 batteries, as well as 20% more power. It also claims that it can be safely recharged twice as many times as similar lithium-ion batteries. Both packs are roughly the same in terms of other specs. 

They can each be used in temperatures below 0 degrees Fahrenheit, and have leak and impact-resistant housing. Based on the stats alone, the takeaway would be that the 5.0 is the better all-around battery thanks to its stronger power output, while the 6.0 would be the choice if you want to run your tools for longer stretches. However, when you factor in real-world user experience, things tilt clearly toward the 5.0 XC.

In many of the negative user reviews for the Redlithium 6.0 on Milwaukee's website, the common culprit is sudden failure. Multiple users claim that, despite a reasonable level of use and proper winter storage, their 6.0 batteries have failed completely after only a few charge cycles. "Charged this battery maybe only 10 or 15 times and today I used it in the multi tool and it died. Won't charge at all," joefromcalifornia wrote. Users on the r/MilwaukeeTool  subreddit have echoed these woes, testifying to the 6.0's higher failure rate. Several users have claimed that their 6.0 battery packs did not even last a full year before dying. "The 6.0 literally have like a 50% failure rate. They are terrible batteries," u/Griffman1987 commented.

In fairness, the 5.0 High Output battery has its share of detractors as well. Several user reviews on the Milwaukee website cite structural issues with the battery, such as damaged connection tabs and casing.  "I have 8 M12 XC 5.0 batteries, and they're barely a year old. 5 of the 8 batteries won't charge, due to what I believe are imbalanced cells," DCDreamer45 explained. However, compared to the complaints of failure on the 6.0, the cited issues with the 5.0 batteries seem much fewer and further between. Reddit users often recommend buying the 5.0 over the 6.0 because it delivers a greater burst of power, increassing the capability of your tools. "6.0 is a higher capacity, but the 5.0 HO can put out more power at once," u/Patriae8182 explained.