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CTEK D250S [Power Management CTEK-D250S]

The CTEK D250 Dual is a 12 volt 20 amp DC to DC Charger integrating a high efficiency MPPT Solar regulator.  It also functions as an automatic battery isolator.


So why do we need a DC to DC charger? After all, our vehicles alternator will charge our second battery… won’t it?

Manufacturers of modern vehicles are required to meet certain targets with regards to pollution, fuel economy and efficiency (EURO 5 for example). As a result, vehicle alternators are now very clever devices, controlled by the vehicles engine computer. Now the alternator and its control systems are designed to do its task with best efficiency… that is, run the vehicles electrical systems.  It was never designed to correctly charge an auxiliary deep cycle battery!!! The math are relatively simple. Modern alternator output voltages are not nearly high enough for effective charging (typically just 13.2 to 13.4 volts), but we need 14.4 to 14.6 volt to charge most cyclic batteries. A DC to DC charger solves this problem by ‘boosting’ the low alternator volts to a more suitable voltage for fast, safe and efficient charging. This results in longer battery life and better performance.

The D250 Dual also have a ‘multi power point tracking’ (MPPT) Solar regulator built in which can, depending on the installation, charge the battery with both alternator and solar at the same time.


The D250S Dual refines all DC sources including alternators and solar power, to perfectly  match the amount of charge the battery requires whilst minimising charge time. The D250S Dual is a 20A  multi-step charger that automatically  adjusts the charging voltage and current according  to the battery state of charge and temperature to ensure that the battery is safely optimised for performance.

The D250S DUAL charger obtains its energy from DC sources such as alternators, solar panels or wind power and optimises this power to meet the charging requirements of different battery banks.
The D250S DUAL automatically selects the best connected DC energy source (of 2) for the purpose and switches between these energy sources to achieve high efficiency multi-stage charging.

The D250S DUAL is particularly suitable for charging vehicles that do not have access to grid power supplies. Charging automatically starts as soon as DC energy is provided to the charger, for example, from alternators when a vehicle is started or from solar panels when connected. The D250S DUAL ensures that your batteries are always in good condition, quick charging and have long battery lifetimes.

The D250S DUAL is a fully automatic 5-stage charger that supplies 20 A to 12 V batteries of 40–300 Ah. The charger is IP65 classified (water jet and dust protected and approved for outdoor use) and protects vehicle electronics. It is suitable for all types of lead-acid batteries (Wet, MF, Gel, AGM). It is supplied with a 2 year guarantee.


  • Multi-step charging from alternators and solar panel. 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 avoiding 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 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.

Faster Charging

The 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 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, ensuring that the solar and alternator function work in unison to maximise power output.

Key Features

  • 90% efficiency
  • Adapts to parallel energy sources, use with alternator, solar  or both
  • Automatic starter/service battery separation
  • Input  voltage 12.9-22V DC; 14.4V Charge Voltage
  • Max charge current 20A; charges batteries 40Ah to 300Ah
  • IP65 rated  – splash and dust proof
  • Temperature sensor
  • 2 year warranty

Key Technical Data

  • Input voltage: max 22VDC
  • Output voltage: 14.4V at 25°C
  • Charging current: 20A
  • Ripple: <4%*
  • Ambient Temperature: -20 deg.C to +50 deg.C
  • Charger Type: fully automatic 5-stage charger
  • Batteries: Suitable for all types of 12V lead-acid batteries (Wet, MF, AGM and GEL).
  • Battery size: 40-300Ah
  • Dimensions (L x W x H): 192x110x65 mm (LxWxH)
  • Insulation: IP 65 (splash and dust proof)

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  • Product Code: CTEK-D250S
  • Availability: In Stock
  • 0.00€
  • Ex Tax: 0.00€

Tags: ctek, d250s, power, management

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