Can You Charge A 40V Makita Battery With An 18V Charger?

If life were clean and simple, you would always have the right charger for every rechargeable battery. Things happen, though, be it a messy or chaotic move or simply the wear-and-tear of many years of use. So, what if you're left with a lower voltage charger and a battery that requires more than double that amount?

Looking at Makita brand's 40V battery compared to its 18V charger, you can get a sense of the relationship between different batteries and chargers. In the case of something like Makita's BL4040DC1 40V Max XGT battery and Makita's DC18RC 18V LXT charger, there simply isn't one. Not only is the Makita battery slightly larger, at 3.2 inches wide compared to the 3-inch 18V battery, the connectors are also completely different.

With that in mind, that also means you won't be able to use a 40V battery on any of Makita's power tools that fit an 18V battery. If you have any question as to which is which, the 18V line of tools are branded as LXT. The 40V line is branded as XGT (think "extra-giant" for an easy way to remember that XGT is bigger). Now, none of this is to say there isn't any compatibility, it just depends on which direction you're trying to go.

While your 40V batteries won't fit in the smaller 18V charger, there is a way to make your LXT (18V) batteries compatible with an XGT (40V) charger. Even though the 18V is smaller, it doesn't just slide onto the 40V port, so you'll need to have an adapter. To make the two lines compatible, Makita released the 18V LXT Adapter for XGT Chargers. The adapter slips easily onto any 40V XGT charger and features a connection for an 18V battery.

You may worry about damaging the 18V battery on a higher voltage charger. After all, doing so in any other scenario can ultimately diminish the performance and lifespan of the battery. However, Makita's adapter features the necessary failsafe protection to keep the 40V charger from negatively impacting the 18V battery. Among its features is overload, over-discharge, and overheating protection. Overload protection, specifically, is what makes it possible to charge any size 18V LXT battery, from the 2.0Ah Compact Lithium-Ion to the 6.0Ah Lithium-Ion, on the higher-voltage charger.

This doesn't mean you can take the Makita adapter and put it on your 40V tools, though. It's designed specifically for the charging base for 40V batteries, and can't be used to put 18V batteries in 40V tools. As YouTuber Tools & Stuff demonstrates, the adapter is configured slightly differently than the batteries themselves, with a slightly altered mold than what's on the battery connection of the tools. You'll need to stick to the right voltage for each power tool.

Speaking generally and not just focusing on Makita products, 40V batteries are physically larger than 18V batteries. Whether you're shopping Ryobi, DeWalt, or any other power tool brand, you'll find this to be true. That's because the 40V needs more power cells to reach that output. Since they have more power cells, these larger batteries are able to keep more power-demanding tools running efficiently. For example, you'll likely see 40V batteries used in gardening tools like a chainsaw because it needs more power than an 18V battery can provide. Alternatively, power tools like a drill will typically use an 18V battery because it requires less power to get the job done.

This is typically where the differences between 18V and 40V batteries end. Despite having more power cells, charge times are very close. The 40V battery, specifically Makita's Max XGT, takes 45 minutes to charge, whereas the 18V LXT only takes 40. The voltage is also not the only determining factor for how long a battery will run. That's going to be determined by a mix of volts and amps, though a higher voltage battery with the same amps as a lower voltage battery will last longer.