While the field of advanced batteries is expanding, only two
Most major professional power tool manufacturers now have some sort of advanced battery system on the market. Among them, only two adopted the concept of switching voltage. We are looking at DeWalt FlexVolt vs Metabo HPT MultiVolt batteries to see how they are similar and how they are different.
Which comes first?
DeWalt pioneered its voltage switch group in 2016. DeWalt FlexVolt technology took us by surprise at the launch event.
Since then, only Metabo HPT has decided to follow DeWalt down this path. The MultiVolt battery was released in 2018, at the same time that Hitachi Power Tools announced a rebrand to Metabo HPT.
How does a voltage switch battery work?
When you build a lithium-ion battery pack, you connect individual cells either in series or in parallel, or a combination of both. Connecting in series increases the voltage, and connecting in parallel increases the amp-hours. Even though you can change the wiring to adjust the voltage or amp hours, you can get the same total watt hours out of these batteries.
To make a battery pack that can switch voltages, you need to start with a few cells that work together. For example, you can make an 18V, 5.0Ah battery or a 36V, 2.5Ah battery from the same 10 cells.
To make a battery pack that switches between 18V and 36V, you can use 10, 20, 30 or more batteries as long as they come in packs of 10. A battery pack that switches between 18V and 54V (20V and 60V max) requires a setup of 15 cells.
Once in place, electronic communication between the tool and the battery tells the battery pack which connections to use to get the correct voltage for the tool it's using.
same kind of different
DeWalt's FlexVolt system switches between 20V Max and 60V Max (18V and 54V nominal). This requires a battery pack containing 15 cells. Currently, DeWalt has FlexVolt batteries in 2Ah/6Ah, 3Ah/9Ah and 4Ah/12Ah*.
NOTE: The first number is the amp-hours at the higher voltage and the second number is the amp-hours at the lower voltage.

The Metabo HPT's MultiVolt system switches between 18V and 36V, which means its core power source is a smaller 10-cell battery pack. The initial excitement revolved around the battery pack running a 4.0Ah/8.0Ah configuration. Recently, 2.5Ah/5.0Ah ultra-thin battery packs have also entered the market.

Both systems have pros and cons. DeWalt's FlexVolt is bigger and heavier, but its two larger battery packs have higher energy capacity, and the 60V Max is likely to be more powerful than the 36V.
Metabo HPT's MultiVolt is a smaller, lighter battery pack with a lower capacity than the 3.0/9.0Ah and 4.0/12.0Ah FlexVolt batteries. Its 36V system doesn't have as much power potential as the 60V Max series.
The higher capacity and power of the DeWalt can be a big plus when you're working with tools like table saws and miter saws. DeWalt even has a 15Ah FlexVolt battery on the market.
However, one of the key features of both systems is that these higher voltage battery packs can also power tools that require 20V Max or 18V batteries. You might not mind a bulky FlexVolt battery on a reciprocating or circular saw, but the Metabo HPT's light weight and size is a huge advantage over some of its drills and impact wrenches, especially in the slim in packaging.
Bonus: AC Power
Both systems have AC adapters available, but they affect the lineup quite differently.
Currently, DeWalt only has one tool-specific power adapter: the DeWalt FlexVolt 120V Miter Saw. It runs on (you guessed it) 120V and requires 2 batteries or an adapter.

All Metabo HPT MultiVolt tools are compatible with their AC adapters.

Neither adapter will work with every brand of 18V or 20V Max tool.
the bottom line
It's interesting how two brands take the same concept and create two very different systems out of it. Choosing which one is best for you really comes down to your personal priorities.
Want higher voltage and capacity? The DeWalt FlexVolt is the way to go.
Prefer a smaller footprint, lighter weight AC adapter that fits across your entire production line? Use Metabo HPT MultiVolt.
Which do you prefer? Tell us in the comments below!