The green battery wall shows a dual nature: one half of the packs plug in on a stem while the other half slide in flat, and among the two methods there lies every question you have regarding which one should match which.
The rules regarding Ryobi battery compatibility are two in number. The first is that 18V and 40V batteries must not be mixed, neither in practice nor in a safe manner. The second is that on the 18V ONE+ platform, each battery is compatible with every tool all the way back to 1996. That is the complete picture; the rest consists merely of making a choice.
The guide for Ryobi batteries covers the four platforms, explains why the 40V battery won't even fit into an 18V tool, outlines what the ONE+ everything-fits rule means for older tools, details what the HP and EDGE batteries actually offer, and helps you decide between 18V and 40V; information regarding the cross-brand rules can be found in our power tool battery compatibility guide.
The four platforms, walled off
Under its one green roof, Ryobi operates four separate battery systems and they share nothing.
| Platform | Voltage | What it powers |
|---|---|---|
| USB Lithium | 4V | Small screwdrivers, rotary tools, lights |
| ONE+ | 18V | More than 300 hand and bench tools |
| 40V | 40V | About 85-plus yard and outdoor tools |
| 80V | 80V | The big stuff, like riding mowers |
Each platform forms a closed system; a pack from one row in the store cannot be used with a tool from another row, even if both of them are of a green type. Although the figures regarding the tools are Ryobi's own marketing figures, there is a real engineering barrier between the platforms. When you want to compare batteries from all the different brands, our electric tool battery guide includes the entire range.
Why 40V never fits 18V: stem vs slide
The two principal platforms aren't even connected in the same manner.
The 18V ONE+ pack has a stem configuration: there is a cylinder which projects from the battery and then fits into the tool. The 40V pack, on the other hand, has a flat slide design and runs on rails, with its contacts located on the surface. The two designs differ in their shape, in where the contacts are placed, and in the way the latch functions. A 40V pack will not click into an 18V tool without cutting through the plastic, and if you do cut the plastic, you'll have created a more serious issue.
The motor and wiring of the tool are only rated at around 18 volts, not 40. If you supply it with 40 volts you're guessing whether it will overheat and melt, and since Ryobi's warranty does not cover altered or modified equipment the melted tool will have to be kept by you. "Can I get it to fit" is the question we are asked more than any other, and the answer in all cases is that the platform wall is being generous.
ONE+ 18V: the everything-fits platform
Here's the good news, and that's the reason why ONE+ has the reputation it does.
On the 18V ONE+ platform, all batteries are compatible with all tools, and Ryobi's commitment is that this applies in every case—so a new lithium battery can be used in a ONE+ tool that initially came with a NiCad battery. Since the stem has always been the same, compatibility has never been compromised.
People send us photographs of 1990s drills and ask whether or not they are too old, only to be surprised by our answer, which is that if the drill shows ONE+ then it isn't too old.
The rule applies in the opposite direction as well. An HP battery will work in a simple non-HP tool, but it won't enable the extra performance, more on that later. As for the straightforward answer: if it states ONE+ 18V, then it will fit.
HP and EDGE: the battery tiers
In the ONE+ model the batteries are offered in different grades and Ryobi has been changing their names, which is the reason why the shelf appears confusing.
| What it's called now | What it used to be | The short version |
|---|---|---|
| 18V ONE+ Lithium | High Performance (HP) | The everyday upgrade tier |
| 18V ONE+ Lithium EDGE | High Performance EDGE | The premium tier, tabless cells |
The EDGE packs use 21700 tabless cells together with a cooling system which Ryobi refers to as Cool-Core Pro. Ryobi's claims regarding the EDGE are substantial: they state that the product offers up to double the power and up to four times the runtime as compared to the standard HP packs, along with faster charging. Treat those figures as marketing claims until you have tested them yourself.
The aspect that most buyers fail to realise is that the extra power only becomes available when the battery is used with a matching HP or HP+ brushless tool. If you fit an EDGE pack onto a regular ONE+ tool it will operate just like a standard battery. You can't simply get more power by buying a better battery.
18V or 40V: the decision
Once you examine how the tools actually operate, the question of the platform has a simple answer.
The ONE+ 18V tools work in bursts: you squeeze the trigger, carry out the cutting or driving for a few seconds, and then release it. This applies to drills, drivers, saws and nailers, and the battery then has a break between bursts.
Tools that operate on 40 volts run continuously; for example, a mower, a blower, or a chainsaw will stay at full throttle throughout the entire job, which can last thirty minutes or more. That's the basic idea, and it corresponds clearly to the rule that bench and hand tools are 18 volts while ongoing garden work is 40 volts.
The decision tree:
- Mostly indoor and hand tools? ONE+ 18V, no contest.
- Mostly sustained yard work? 40V, and buy for runtime.
- Both? Most people start with ONE+ and add 40V for the two or three yard tools that really earn it, because running a mower is what 40V exists for.
If you run red tools too, the Milwaukee M18 battery guide covers that platform's version of all this. And once you know your platform, our Ryobi compatible batteries collection has the packs to match.
Common questions about Ryobi batteries
Are Ryobi 18V and 40V batteries compatible?
No. They're two separate closed platforms with different connectors, a stem on the 18V and a flat slide on the 40V, and different voltage classes. They don't physically fit, and they were never designed to.
Are all Ryobi 18V ONE+ batteries compatible?
Yes. Every ONE+ 18V battery fits every ONE+ 18V tool, all the way back to the tools from 1996, and HP batteries work in non-HP tools too.
What's the difference between HP and EDGE batteries?
Both are high-performance tiers. EDGE, now labeled 18V ONE+ Lithium EDGE, adds 21700 tabless cells and Cool-Core Pro cooling, and Ryobi claims up to double the power and four times the runtime. The extra only shows up on matching HP or HP+ brushless tools.
Can I use a 40V battery in an 18V tool?
No. The connectors don't match, the tool's motor is rated for 18 volts, and forcing 40 volts in risks overheating and a melted tool. Modifications also fall outside Ryobi's warranty.
Which should I buy, 18V or 40V?
Match it to how the tool runs. Burst work like drills and saws belongs on 18V ONE+. Continuous yard work like mowing and blowing belongs on 40V. Most people start on ONE+ and add 40V for the yard tools that earn it.
At first, Ryobi's battery range appears complicated but there are two rules listed beneath it. The platforms aren't interchangeable, and ONE+ is compatible with all the products it has ever made. If you match the shape of the connector, stick to the platform, choose the tier that you actually intend to use, the green wall will then sort itself out.
References & Sources
- Ryobi official site (battery platforms, ONE+ compatibility since 1996, HP and EDGE tier claims, warranty exclusion for modified equipment)
Need a replacement?
If you're familiar with your platform, then you should get Ryobi-compatible batteries. We carry ONE+-compatible battery packs covering the entire capacity range, so the matching has already been dealt with, and if you have any questions you can ask a real person via our contact page.