Amilo Laptop 2512 battery charging problem?

In the last two days my charger charges the battery but then stops (according to the icon in the task bar). If I disconnect the charger and reconnect it starts again. Disconnecting the battery unit also has the same effect i.e starts recharging for a while and then stops. Do I need to replace the charger or the battery or is there a software problem? The battery is the original and is now 3 years old.