When it comes to the 20v vs 18v debate, almost every DIY fan will tell you that 20V tools have more power than 18V.
And they’re all wrong.
OK, I know – bold words. Got any proof to back that up?
Well keep reading and hopefully I’ll prove it 🙂
(Before I set about convincing you that 20V being more powerful is a bunch of crap, let me say that my opinion is based on an article from David C Smith on Pro Tool Reviews and a boatload of research that I did).
So why isn’t 20V more powerful? Let’s find out.
What’s inside a battery pack?
Battery packs are made up of individual batteries that are wired together in a series of five batteries.
Groups of five batteries are then wired in parallel with other groups of five batteries.
That’s true for both 18v and 20v battery packs.
The picture below shows a Makita battery pack that has two groups of five batteries that are wired together in parallel.
This increases how long the battery pack lasts. That’s measured in amp hours and for power tool batteries is usually expressed in Ah (example – DEWALT DCB205-2 20V MAX XR 5.0Ah Lithium Ion Battery).
It also increases the batteries capacity, which is measured in watt hours.
How is the voltage of a battery pack calculated?
It doesn’t matter if you’re looking at 20v vs 18v battery packs – their cells are the same.
They almost always have a nominal voltage of 3.6V and a maximum voltage of just over 4V.
Nominal voltage means the expected, average voltage you’ll get from a battery. The actual average voltage you get from a battery can vary but usually it’s pretty damn close to 3.6V.
And the maximum voltage is the theoretical highest voltage you can get from a battery. In the case of 18V and 20V battery packs, the max voltage of the cells in them is just over 4V.
You might not care about any of this but it’s important when it comes to 20v vs 18v.
Why? 18V and 20V use the same size and type of battery cells that are wired together in the same way.
So how come one puts out 18V and one puts out 20V?
Well, that all comes down to how you calculate the voltage…
The voltage of 18V packs is measured using the nominal voltage:
3.6V (nominal voltage) X 5 cells = 18 volts
The voltage of 20V packs is measured using the maximum voltage:
4V (maximum voltage) X 5 cells = 20 volts
So 18V is calculated using the expected average voltage. And 20V is calculated using the theoretical maximum voltage.
Why is that important? 20v vs 18v isn’t a valid comparison. It’s like comparing the average speed of a car to the theoretical maximum speed of a car.
20v vs 18v – which is better?
Now we know that theoretically 18V packs have the same nominal power as 20V packs, we should talk about which one is better in the real world.
Theoretically, a 20V battery could give you more maximum power that an 18V.
But that’s only if the 20V max tool has been designed to operate better at maximum voltage, than at minimum voltage, by people who know what they’re doing. And if you’re pushing the tool to it’s maximum each time you use it, which most people don’t usually do.
So is 20V better than 18V?
Honestly, that depends on the particular brand and model of tool that you buy.
Why? Because Makita are known for making awesome tools with plenty of power and that Chinese drill looks like it would have problems driving a screw into pine…
So in this case, I’d be willing to bet a million dollars (OK, $50) that the 18V Makita has more power than the 20V Worcraft drill.
In the end, 20v vs 18v doesn’t really matter.
In fact, in my opinion, the only reason to consider battery voltage is if you already own a battery powered tool and want to get another that can use the same batteries.