A control system for a vehicle for optimizing the energy efficiency of a rechargeable electric battery system and/or for optimizing the lifetime of a rechargeable electric battery. The rechargeable electric battery system comprising: the rechargeable electric battery, a temperature management system for the rechargeable electric battery and one or more sensors for measuring one or more characteristics relating to the rechargeable electric battery. The control system comprising a control unit configured and arranged to receive data from the one or more sensors and being coupled to the temperature management system. The control unit being configured and arranged to determine in dependence upon data received from the one or more sensors, a time-weighted-average state-of-health of the rechargeable electric battery. In dependence upon the determined time-weighted-average state-of-health of the rechargeable electric battery, the control unit is configured and arranged to manage the temperature management system and thereby manage the temperature of the rechargeable electric battery for optimizing the energy efficiency of the rechargeable electric battery system and/or for optimizing the lifetime of the rechargeable electric battery.