Ryobi manufactures cordless power tools, many of which are powered by an 18 volt battery pack. Older Ryobi 18 volt battery packs contained 15 nickel cadmium cells, each producing 1.2 volts. However, recent advances in battery design mean that Ryobi now produce 18 volt batteries using lithium ion cells. Li-ion cells produce 3.6 volts and therefore only require five cells for a full battery, making the packs much lighter and smaller. However, battery packs containing Li-ion cells have power surge breakers built-in to ensure they don't get overcharged. For this reason, they should only be repaired professionally. If your Ryobi battery pack contains NiCad cells and you find the battery goes dead quickly then repairing it is an easy task.
Check the label on your Ryobi battery pack to find out the type of cells it contains: it is clearly labelled. If it contains Li-ion cells, take it to your electrical store to get it repaired. If it contains NiCad cells, put the battery on charge and leave it until it's full. Turn off the charger and put the battery into the device it powers.
Select the lowest power setting on your device. You need to discharge the Ryobi battery slowly.
Turn on the device and let it run continuously until it stops. Once it stops turn it off and let the battery and device cool for about 15 minutes.
Turn on the device. You find it runs again, although it doesn't operate as fast. Let it run until it stops then turn it off and let it cool for a few minutes.
Repeat the process by turning it on, letting it run until it stops, and then turning it off. Do this until the device doesn't turn on. Your Ryobi battery is fully discharged.
Put the battery on charge. Leave it to fully charge: it takes much longer than you are used to as the battery cells have been repaired and can now retain more energy.
Remove the battery from the charger once charged. Insert the battery into the device and use it normally. You will find it has more power and lasts longer between charges.