Cordless battery packs used for powering Ryobi tools produce between 7.2 and 18 volts, depending on the power requirement of the tool. A Ryobi battery consists of multiple nickel metal hydrate (NiMH) or nickel cadmium (NiCad) cells wired in series, which combines the power output from each battery cell (a 7.2 volt Ryobi battery has six 1.2 volt cells). After the battery has been charged and discharged a few hundred times, it stops retaining its power and goes dead quickly. If this happens you need to revitalise your Ryobi battery.
Charge your Ryobi battery until the power level suggests it's full. Position your power tool securely in a vice to ensure the moving parts are not obstructed.
Switch on your power tool and let it run continuously. If you need to keep a switch pressed for it to operate, use electrical insulating tape wrapped tightly around the switch so it remains in the "on" position.
Let the power tool run until it stops operating. Leave to cool down for a while.
Switch on your power tool. It will start to run for a short while, then stop. Repeat the process until it doesn't operate. Test it one more time.
Charge your battery until it reaches full power. It takes a while, as the battery was completely empty. Your Ryobi battery is revitalised.