I have that adapter, too. It's alright, doesn't "click" into place that well though. There are better ones on Etsy but they're also [last I looked, at least] 2-3X the price.
There are also solid Ryobi 18V battery adapters on Etsy, too, and I have a few of those as well. I used one of the 18V adapters for my kids modded PowerWheels, so that I could ditch the 2 lead-acid batteries which didn't last very long & now I can drop in any of my higher-capacity [4-6AH+] Ryobi batteries & they can drive around for an hour or so. Then I just pull [or swap] the battery, and throw it back on the charger. I did add a cheapo voltmeter to the Powerwheels dashboard, which I keep an eye on & have told my kids that when it hits X number, to let me know so I can swap it.
Note, for anyone considering adapters for Powerwheels/PW mods -- you really want to swap for a 'smarter' ESC if you're going above 12V and/or if you're using LithiumX batteries instead of lead-acid [mainly for accel/deccel, but also to avoid thrashing your gearbox/motors + theoretically safer when using LithiumX batteries].
I'd love to make my Allett 43 use 40V Ryobi packs, but the adapter above isn't "snug enough" out of the box (I have several of that exact adapter) for me to consider it as a viable way to do so -- I think the battery would "wiggle" during use and either lose contact entirely or wiggle enough to have varying levels of contact/poor contact [solveable but more work]. I also don't know if the Greenworks batteries, that my Allet takes by default, have any additional 'data/control' buses that would make a 'straight swap' more difficult to perform. I may look into it closer after it after my warranty is up, though, but I'd start by looking at the Greenworks batteries closer to see what, if any, data and/or 'control' wiring may exist -- and I'd do it in the off-season, last thing I want to do is fry on board on the Allett.
FWIW, buck converters & even adjustable 'step-down' voltage converters exist & are relatively cheap, even. Making this dethatcher run off of a 40V Ryobi battery is absolutely doable, though only with a voltage converter -- giving it the full 40V would almost surely burn the electronics & motor up quite rapidly. IMO it's not worth it, though -- 18V Ryobi batteries are pretty easy to come by, are reasonably priced, and their warranty is solid & Ryobi CS is good WRT handling warranty on failed batteries, in my experience from the few occasions I've had to call in due to a failure (they generally ship you a replacement battery over the phone & tell you to 'go recycle the old one or drop it off at any Home Depot').
If anything, the 40V batteries are the more expensive and "prized" thing to keep at their best performance -- though Ryobi is also good about warrantying them, too. That said, my failure rate is MUCH higher on 40V Ryobi batteries vs 18V (by a large margin).
My 2c.
