Ryobi Adapter

They sell these, but they're underpowered. I'm going to build mine at 20V, that's what the 18V battery measures when it's charged.

I'll start with a 24V transformer. I found a MC33167 that might get it down to 20V (rate 5A). LT1270ACT is rated at 10A

this guy used 20 amps.