Remove the power inverter from its box and examine its pieces. Place it on the floor board nearest the cigarette lighter adapter plug on your vehicle.
Connect the red-positive and black-negative terminals to the mounting screws on the back of the power inverter.
Remove the Ryobi in-car charger from its package and place it on the driver's side floor board and then attach the AC adapter plug to the body of the charger.
Plug the other end of the Ryobi adapter, the one that looks like a standard AC wall unit plug and plug it into the power inverter.
Plug the power inverter end into the vehicle's cigarette lighter and flip the inverter switch to the "On" position. Then power up the charger. Place the lithium ion batteries into the Ryobi charger ports and remove them when the indicator lights on the charger show the batteries have charged.
Disconnect the inverter and power down the charger when not in use so you do not needlessly run down your vehicle battery,