For medical implants it is not only important to have a battery powering the implant with a long run-time, but to know exactly at any point in time how long the remaining run-time is. On the other hand the implant together with its battery shall be as user-friendly as possible requiring no or hardly any interaction with the device except for recharging of the battery. To better address these concerns, a method for determining the state of charge of a battery is suggested comprising the steps: charging the battery, discharging of the battery, predicting the state of charge of the battery using a recharge prediction unit, wherein the recharge prediction unit is disconnected from the battery during the discharging of the battery. The prediction of the state of charge of the battery during the discharge of the battery, i.e. during powering of a device connected to the battery, without carrying out any measurements during the discharging of the battery, enables a local separation of the battery or the implant powered by the battery and the recharge prediction unit during the discharge cycle of the battery.
