D250SA - ctek Dual input 20A charger with selectable charge voltages The D250SA has a wiring harness with a black and a red wire, the red wire must be connected to an Ignition signal wire +15 (DIN 72552). By continuing to use ctek you accept our use of cookies. CTEK D250S Dual alternator to battery charger | Land Mar 30, 2012After much deliberation (between a CTEK and a Sterling) I have just taken delivery of a CTEK D250S Dual alternator to battery charger for my auxillary batteries. The reasons I opted for the CTEK over a Sterling in the end were: (1) the CTEK is also a solar regulator (built in) and will automatically switch between alternator and solar power to CTEK | Battery chargers for all types of vehicles CTEK offers battery chargers for car batteries, boat batteries and motorcycle batteries for professionals as well as consumers. We have chargers for charging in cold and AGM batteries.