Ryobi is a prominent maker of cordless tools and the 14.4 volt models they offer produce a lot of power. This power is great for those that felt cordless tools did not pack enough punch for the work that they do. This power is of course dependent on the battery pack, and battery packs for all cordless tools have a limited life. When the pack on your Ryobi tool begins to show signs of failing, consider rebuilding it yourself.
Take a look at the plastic case of your battery pack and see if it has any small screws that can be removed to allow access to the inside. If it does, remove them, set the pack on its base and take off the top piece of plastic.
Put a chisel tip on the soldering iron and heat it up so that you may cut open those battery packs with no screws. Set the pack on its base and cut through the hard plastic in a line around the top of the base. Remove the top piece of plastic and set it aside.
Look inside and you will notice that the Ryobi 14.4 volt battery pack is made up of 12 individual sub-C rechargeable cells. Take notes on the connections between the cells and how the batteries are arranged. You can then look back to these notes when it is time to put the pack back together so that you reassemble it correctly.
Touch the soldering iron tip to each battery connection to soften the solder, and then disconnect and remove each cell. Do not throw these in the trash, as they are not safe for disposal in landfills. Set them aside for proper recycling.
Clean each connection by firmly using a wire brush on it. This should remove any corrosive build-up and make for better conductivity. Look back at the notes you took and set the new cells in place, just as the old ones were. Solder the new connections.
Set the top piece of the plastic case back on the pack. If it had screws, refasten them securely. For packs that had to be cut open, mix some epoxy adhesive and glue the two plastic pieces together. Let the epoxy dry. Place the new battery pack on the charger, and allow it to charge overnight without interruption before putting it to use.