This battery-trainer / Jogger 12V 300mA fed now for 4 (!) Years the battery of my convertibles, supercharged engine with 193 hp. The battery is now almost 7 years old and starts like the first day. Through the continuous use of the sulfate residues Joggers run well against zero and keep the battery fit! The device is only taken from the electrical system when the convertible -only is driven in good weather, without Winterbetrieb-, then the cable is quickly reconnected to the grid (garage). Very impressive continuous power, playing a simple monitoring with green and red -Erhaltungsstrom- -Ladestrom- telltales! One should evaluate these devices fairly, concerning. Battery life and starting ability, only after 1-2 years.