They are a new type of battery fitted to cars like BMW Efficient Dynamics that work with regenerating alternators.

Your problem is either a weak battery from short run use that does not put enough charge back in. Or the car is suffering a leakdown. Always switch off the radio at the radio, switch off the interior light system entirely. Check the boot light and glove locker lights are going off by setting your mobile phone to record a movie then locking it in the boot and the glove locker. If the light is not going out, take out the bulb.