Are 20V Power Tool Batteries More Powerful Than 18V?

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Power tool batteries are a numbers game; you want stronger performance, you get a battery with higher numbers, plus a compatible tool to plug it into. DeWalt, for example, has several families of power tool batteries, including 12V and 20V. Both of these batteries are used to power hand tools, but if you want a tool with a higher output, you get one that takes 20V batteries.

While the difference between 12V and 20V batteries is fairly apparent, though, what if we narrowed the scope a bit? Once again citing DeWalt, the brand used to sell both 18v and 20v batteries, though the former have been discontinued. If we go by the numbers game again, the natural assumption is that the 20V battery is automatically better. However, in this particular area, that's not quite true. In fact, for DeWalt or any other hardware brand, 18V and 20V batteries are actually effectively identical. That might sound strange, but it actually makes sense if you know the difference between nominal voltage and maximum voltage.

A power tool battery's overall voltage is determined by the combined voltage of the multiple power cells that make it up. An average 18V battery usually has five power cells, each of which has a nominal voltage of 3.6 volts, at least when it's brand new and hasn't bled off any juice yet. In that same vein, a 20V battery also has five power cells, but those cells have a maximum voltage of 4 volts. At a glance, it might seem like the 20V pack's cells are stronger, but that's actually just a result of the particular means of measurement the brand is using.

A power cell's nominal voltage represents how much power it typically puts out when under load, while maximum voltage, also known as rated voltage, represents the most power a cell can put out without endangering itself. In other words, a power cell in either an 18V or 20V pack typically puts out 3.6 volts, but can put out as much as 4 volts. They're exactly the same, it's just that the battery's brand is deliberately highlighting its max potential because it sounds better. It's a marketing gimmick, in short.

18V and 20V batteries are completely interchangeable. If you placed both types on a multimeter, you would get the exact same power readout. One brand may market its 18V packs as 20V in other countries or vice-versa due to different power standards, but it's usually just to make the batteries sound a little bit stronger than they actually are.