I’m looking for a mobile charging station. ‘mobil’ means taking energy from its own built-in source (battery). It is intended to charge the starter battery in car, type AGM, before and after cold season. Car is in use during cold season, only the driving profile may strain the battery very hard. At the parking space no socket ~230V. Take the starter battery out of the car, then carry into the garage/cellar for charging, does not work because car on guarantee. Not really resourceful. Fritec boxes show striking rate of negative reviews (Amazon or something). Truly not available on the market?