tried that.... it's the 18vdc that put me on a dc to dc converter. what works fine w/ a car battery doesn't fly w/ this concept. maybe my converter (1.5 amp) is the issue or the design of the ryobi. it's really got me stumped....
have tried finding a solar inverter small enough so i could try 18vdc to 110vac. tired it w/ one model (power inverter 250) which is too big but only got a fault reading anyway. you can probably hear me scratching my head.....
Do you want a modifed sinewave or a true sinewave inverter? If you did a DC-DC converter from 18.5 to either 10-15.5 or 20-30VDC you could use one of the automotive inverters from PowerBrite