The D250SE is a fully automatic, five-stage charger capable of delivering up to 20A to 12V lead-acid or lithium service batteries with capacities ranging from 40Ah to 300Ah. It features selectable charging algorithms for flooded, AGM, and lithium batteries, and can draw power from multiple sources, including the vehicle alternator, solar panels, or wind turbines. Engineered to perform reliably with modern, ECU-controlled smart alternators, the D250SE maintains a stable output of up to 20A. An integrated temperature sensor optimises charging performance across varying environmental conditions, ensuring consistent and efficient operation. The D250SE is designed for use with solar panels rated up to 300W. However, it can safely accommodate higher-output panels provided the open-circuit voltage does not exceed 23V. In fact, connecting a higher-capacity panel can help offset reduced solar performance during overcast conditions. Additionally, the D250SE incorporates a battery maintenance function that delivers three-second pulse charges to the starter battery every 15 seconds. Charging current is dynamically adjusted based on available solar input and the starter battery’s voltage, helping to maintain optimal battery health. Ideal for campervan applications-particularly those equipped with smart alternators-the D250SE can operate as a standalone solution or in conjunction with the CTEK Smartpass system. The Smartpass 120S is fully compatible with lithium batteries, providing enhanced flexibility and performance for advanced power management setups. Suitable for use with smart alternators? Input Voltage – Volts. 11.5 / 23. Output voltage – Volts. Max 14.4V (14.7V in AGM mode). Charging current – Amps. Input from alternator – V. 11.5v TO 23v. Input from solar panel – V. 11.5V to 23V. >13.1V, for 5 sec. (engine running, alternator charging). Smart alternator cut-in V. >11.8V, for 5 sec. Smart alternator cut-out V. Suitable for battery types. All 12V lead-acid batteries including: Wet, A. M, gel, calcium and maintenance free + LiFePO4 lithium batteries. Power input from solar panel – Watts. Operating temperature range – °C. Minus 20 degrees C to plus 50 degrees C Automatic reduction of power at high ambient temperature. 30 degrees C 16A, 50 degrees C 13A. IP65 (splash and dust proof). This charger can only be used with solar panels that have a peak voltage maximum of upto 23V. Please ensure that your panel is compatible before purchasing. Temperature compensated charging, Reverse Polarity protection. Fully certified for use in vehicles. Dimensions (L x W x H) – mm. 192 x 110 x 65mm.