We all know the square peg in a round hole analogy, and when discussing the use of one manufacturer’s battery packs in another manufacturer’s power tools, it may very well be an apt one. Is compatibility a problem? Are they interchangeable?

We’ve written of batteries and battery packs in the past, and you’ll find our most recent piece here about Kobalt and DEWALT batteries.

We want to remind you of a few things to keep in mind about batteries and battery packs for power tools:

Manufacturers make the battery packs for their tools.
The battery packs are made to fit well in the battery slots of the power tools for the delivery of full power and to be stable in the slots.
There is no universal standard for battery pack sizes and battery slots.

All of that having been said, you can probably see where we’re heading in this article and the answer to the main question asked – Will DEWALT batteries fit Ryobi tools?

The batteries we are talking about are lithium-ion batteries, a recent technology that has virtually replaced the nickel-cadmium battery technology that powered so many tools previously. Lithium-ion batteries are rechargeable and are comprised of cells with voltage ratings of 1.2 volts, 1.5 volts, or 3.6 volts. These cells are combined in batteries with voltage ratings of between 3.6 volts up to 48 volts.

The various manufacturers then build battery packs for their tools that are designed to fit well with them. Batteries communicate with the motors of the power tools they are affixed to, and the whole relationship between the battery pack and motor produces an efficient and effective tool.

The majority of power tools run on an 18V battery pack. But what about the DEWALT 20V Max battery pack? Well, that’s an interesting question.

As we told you, battery packs have the battery cells inside them in some configuration and number. Manufacturers in the US, including Ryobi, all run on an 18V battery platform; DEWALT runs on their 20V Max systems.

All of these batteries have 5 cells, each 3.6V, wired in a series, both the 18V and 20V Max. Do the math: 5 x 3.6V = 18V. But, then you must consider both the nominal and the maximum voltage ratings:

Nominal: the amount of voltage when a cell begins to discharge;

Maximum: the maximum voltage capacity of a cell.

Each cell has a nominal voltage of 3.6V and a maximum voltage of a little over 4V. That latter math is easy: 5 (cells) x 4V = 20V maximum. Thus, the DEWALT 20V Max label. DEWALT chooses to use their battery’s maximum voltage rating, while the rest choose to use the nominal voltage rating. It’s a label thing and a marketing tool.

For the purpose of this piece, we are addressing only the 18V and 20V Max battery packs and not a 40V pack. We also are not going to discuss charge times or charge holding times among the various battery packs.

Ryobi power tools use the Ryobi One+ battery pack. Ryobi also keeps things simple with their tools and battery packs – all of its 18V tools under its One+ line use the same battery pack. They use a push-in style fitting that is completely interchangeable among all of their power tools.

Now that we know a little bit more about power tool batteries and battery packs let’s tackle the main question and give you the answer.

As we said, each manufacturer makes battery packs to fit their own power tool lines, but not for other manufacturers’ power tools. But, there are almost always workarounds, and we woodworking enthusiasts have come up with some of our own in our shops – jigs for this and that, etc. These workarounds are necessary because the battery packs, in fact, are interchangeable only with modifications.

When it comes to using one manufacturer’s battery pack on another manufacturer’s power tool, the same holds true – the adaptor. And in the case of DEWALT battery packs and Ryobi power tools, there is the Badaptor DEWALT to Ryobi Battery Adaptor.

As you might have guessed from its name, it is made specifically for using DEWALT battery packs with Ryobi power tools. It allows you to use the DEWALT battery pack with the extensive line of Ryobi tools and enjoy full use of both, sparing you from having to maintain two sets of battery packs (money, storage, charging, etc.)

It’s a workaround, yes, but there is a question to consider – your warranties for both the battery packs and the power tools. As we recommended in our previous articles on the battery pack compatibility question, be sure to check your manufacturer’s warranty documents that came with each. We suspect you’ll find warranties will be voided by the use of an adaptor.

That will require a value and budget judgment from you – to save money and jeopardize warranties you are paying for when you purchase each; or spend the extra money to preserve the warranties.

If you want to learn a little more before you make your decision, here’s a video that explains and demonstrates the adaptor.

Square pegs can be made to fit in round holes with modifications, and battery packs can be interchangeable with modifications. The question, though, is whether either is worth voiding your warranty. Only you can decide, but it can be done.