toolboy's Corner: Ryobi 40v to 18v Adapter

After constructing the 18v to 40v Adapter and Power Bank about a year ago, it was only a matter of time before I constructed an adapter to go the other way. This device allows one to use a Ryobi 40v battery to power just about any Ryobi 18v tool. I say "just about" rather than "all" because I'm sure there are a few 18v tools which cannot be used with this adapter due to the physical size of the 40v battery. For example, several wet-use tools such as the RY120350 EZClean 320PSI Power Cleaner have a plastic cover for an 18v battery which isn't large enough to cover one of these adapters plus a 40v battery.

How it Works

The heart of this adapter is an adjustable voltage output DC-DC bucking adapter. Conveniently, the adapter is small enough to fit entirely within a full-height 18v battery shell. All in all, this was a fairly simple project once I'd collected all the needed parts. I constructed two of these, one using a P104 battery and the other using a P108 battery.

The Build

Parts required: