TomTom portable GPS devices are sold with a rechargeable battery. Over time, this battery can wear out and will not be able to hold its charge like it once did. Instead of purchasing a new TomTom, it might be more cost effective to replace the battery. Keep in mind, the TomTom Go 300 is not meant to be dismantled: You might void the warranty if you take the device apart or you risk damaging the TomTom further. If you decide to replace the battery, it might be helpful to take notes and pictures at each step to aid in reassembling.
Remove the front screen by prying it from the back of the device. You can use your fingernails or a flat screwdriver to help. Be careful not to break the screen during removal.
Undo the initial set of screws with the T8 screwdriver. These screws hold the internal compartment together. Place the screws off to the side.
Remove the internal compartment. Pay attention to how the compartment fit in, this will be important in reassembling.
Peel back the foil around the speaker. You will see two screws, remove them with the T8 screwdriver. These screws hold in the speaker. Move the speaker aside without disconnecting.
Move the metal box, which is revealed after moving the speaker, to the side. With the box off to the side, you see the battery holder.
Unscrew the battery holder with the T6 screwdriver. Do not disconnect any wires. Be aware that you are just manoeuvring pieces so you have access to areas without disconnecting any wires or plugs.
Unclip the old battery, replace with the new one and reassemble the unit. The unit will power up as soon as you replace the dead battery with the new one.