D250T is a 24 V DC battery charger for dual battery systems with a starter battery and a second battery. D250T can charge and maintain the second battery via the alternator as on-board charger while the engine is running. Thus, the second battery is sufficiently charged upon arrival at the destination. D250T is a fully automatic four-stage DC charger that supplies up to 10 A current for charging 24 V lead-acid battery systems. The charger is also a battery insulator, which separates the second battery and the starter battery. This prevents the battery from discharging when the engine is not running. The D250T ensures that the second battery always receives the optimal charging voltage, shortens charging time, and completes the charging process to 100%. The battery is charged in a stable and efficient manner, regardless of generator power or cable resistance. D250T reduces environmental impact and reduces maintenance costs through longer battery life and reduced maintenance requirements