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The CTEK D250S is a Premium Battery Isolator, a Smart Power Relay, Solar Panel Voltage Controller with MPPT solar power management functionality and a temperature compensated 20A smart battery charger all combined into one multi-functional product!

The D250S DUAL on-board charger, charges while you drive; it gathers energy from multiple DC power sources (the alternator(s), solar panels and/or wind power generators) and optimizes power to properly charge your service battery bank with microprocessor controlled smart charging algorithms and provides temperature controlled charging to meet the charge requirements of your service battery bank in any weather. It increases simplicity and reliability by eliminating the clutter of many individual components including battery switches, secondary battery isolators, relays, load managers, low voltage alarms and cutoff’s, separate solar panel and wind generator voltage controllers, etc.

The CTEK D250S Dual on-board charging system optimizes the charge generated during driving in order to provide you with more battery power and capacity when you need it.

  • High Efficiency Power Management
  • Suitable for all 12V lead acid batteries
  • Simple to install and use – Fully Automatic
  • Multi-step charging from alternators and other DC sources such as solar panels
  • Automatic starter/service battery separation.
  • Solar panel voltage regulator with Maximum PowerPoint Tracking (MPPT), synchronizes with other power sources such as alternator and/or wind generator
  • Maintenance charge of starter battery via solar panel
  • High vibration resistant design


  • Multi-step charging from alternators and solar panels
  • Battery separator that eliminates diodes and VSR relays
  • Maintenance charge of starter battery
  • Solar panel regulator with Maximum Power Point Tracking, synchronised
    with other current sources such as the alternator and/or wind
  • Simplified installation of remote batteries for bow thrust of anchor winch


  • Maximised battery life due to minimised undercharge time
  • Maximised battery capacity when the battery is kept fully charged to avoid harmful sulphate crystals on the lead plates and stratification of the battery acid.
  • Ability to take charge automatically from any power source that is connected to the CTEK D250S DUAL
  • Reduced charging times and costs by decreasing engine idling and the dependency on AC power onshore through efficient use of alternator and solar power
  • Reduced environmental impact through extended battery life and a reduced idle time
  • Minimal installation time and cost

Suitable For

  • Boats
  • Campervans and RVs
  • Caravans
  • 4WDs
  • Housing that rely on generators for extra electricity

Compatible With

CTEK Smart Pass

Faster Charging

The CTEK D250S Dual is a 5-step charger that automatically adjusts the charging voltage and current according to the battery state of charge and temperature – reducing a battery’s charge time. A sensor on the CTEK charger senses the battery temperature and adjusts the required charge by increasing the voltage in cold weather ensuring the battery is fully charged, and dropping the voltage in hot weather to avoid the problems of overcharging. With the CTEK D250S Dual , vehicle owners can be confident that their battery will always receive the optimal charging voltage, with reduced charge time and while ensuring the charging will be 100 % complete.

Solar Connection

The D250S Dual has the additional benefit of an auxiliary input which can be connected directly to solar panels without the need for a regulator, offering free power from the sun. D250S Dual has a built-in Maximum Power Point Tracker (MPPT) that helps the solar cells produce power as efficiently as possible by taking the most efficient source of energy from the solar panels automatically, and then using the power to charge the battery. The MPPT searches for the most effective combination of solar cell voltage and current, which ensures that the solar and alternator function in unison to maximize power output.

Technical Data

Spec Data
Input Voltage 12.9 - 23VDC
Charging voltage 14.4V (Temperature Compensated – Higher for cold, Lower for hot)
Charging current Max 20A
Type of charger 5 step, fully automatic charging cycle
Type of batteries 12V lead-acid batteries (Wet, MF, GEL and AGM)
Battery capacity 40-300Ah
Insulation IP65 (splash and dust proof)
Warranty 2 Year Limited Warranty
Certification Meets ignition protection test requirements of the US Coast Guard stated in Title CFR 183.410
Article Number 56-677

Guaranteed Quality With CTEK

CTEK offers a 2 year guarantee on all DC/DC chargers. CTEK customer support is an appreciated service, both with regard to general questions or specific issues related to charging and CTEK chargers. Safety, simplicity and flexibility characterizes all products and solutions developed and sold by CTEK. CTEK supply chargers to more than 60 countries throughout the world. CTEK is also a reliable OEM supplier to many of the world’s most prestigious car and motorcycle manufacturers. Contact customer support.

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