CTEK D250S Dual DC - DC 12V 20 AMP 5-step Charger Review Photo:
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Steane Klose | Jun, 16 2011 | 9 Comments


Price: $350 - $400 online

  • Optimises battery life
  • Charges batteries using alternator power, solar power or both
  • An easy to install, user-friendly dual battery system.


The CTEK D250S Dual is an in-vehicle dual-battery management system. It features a starter battery isolator and a five-step charger that automatically adjusts the charging voltage and current according to the auxiliary battery’s state of charge and temperature – reducing a battery’s charge time.

A sensor on the CTEK charger measures the battery temperature and adjusts the required charge by increasing the voltage in cold weather ensuring the battery is fully charged, while dropping the voltage in hot weather to avoid the problems of overcharging.

If you own a 4WD and wish to run accessories like fridges or lighting from an auxiliary battery, then the D250S Dual makes the setup of an efficient dual-battery system very easy.

A basic solenoid style dual-battery system is generally only ever capable of charging an auxiliary battery to around 80% capacity, and this is a problem that is compounded when - invariably - more than one battery type is used (most dual-battery set-ups will combine a wet-cell lead acid starting battery with a Deep Cycle auxiliary battery of the Absorbed Glass Mat (AGM) or Gel type).

Over time, the auxiliary battery can lose its charge and even fail prematurely.

The D250S is able to manage multi-battery applications that use mixed battery types, and also allow input from solar panels for additional charging.



The D250S is suitable for any dual-battery setup: in cars, 4WDs or even boats.

In our case and for the purposes of testing this product, we fitted it to the tray of a 2007 Triton and are using it to charge a 100A/h deep cycle AGM battery, that in turn runs a 47-litre ARB fridge.



This is where the benefits of such a complete system can be seen first hand. The D250S is a cinch to fit. The hardest part about our fitment was running the power leads from the starting battery through to the tray.

Easy-to-follow instructions are provided with the purchase of the D250S, but it really was as simple as the following;

  • Mount the D250S in a suitable location near the auxiliary battery
  • Run a fused cable from the ‘+’ terminal of the starting battery to the ‘IN’ terminal of the D250S
  • Run a fused cable from the ‘+’ terminal of the auxiliary battery to the ‘OUT’ terminal of the D250S
  • Run a cable from the ‘-’ terminal of the starting battery to the ‘-’ terminal of the D250S
  • Fix the battery temperature sensor close to the ‘+’ terminal on the auxiliary battery
  • Connect solar panel inputs if you plan to use solar panels for recharging

There is nothing to adjust. Simply turn the vehicle on and check that the indicator lights on the D250S are illuminated as described in the instructions.

A dual-battery system really doesn’t get any easier than this. The D250S even allows you to run narrower gauge cable and earth-to-body/chassis connections (rather than back to the starter battery), for those looking to install in ute trays like we did.

The hardest part of the process is working out your cable runs and arranging to have the fittings crimped by your local auto electrician.



We fitted the D250S about two months ago, and while it’s too early to determine the long-term performance of the system, all of the signs are good.

We’ve fitted the system to a vehicle that spends most of its time on long trips, most recently from Melbourne to Port Macquarie and return.

During this trip the fridge was been left to run for periods of up to two days (without charging of the auxiliary battery) without the fridge’s low-voltage cut-out turning it off.

We have a number of trips planned this year, including a 4WD trek to the Snowies, so we’ll continue to test the performance of the D250S and update this review with our findings.


TMR Verdict | Overall

If you are serious about installing the best type of dual-battery system, one that guarantees to keep your batteries in healthy working order, then arguably the only way to go is a DC to DC charger like the CTEK D250S.

In the CTEK’s case it is a very simple fit, requires no user input during or after installation and is really the ultimate in set-and-forget dual-battery technology.

That it includes an input for solar power is a bonus, especially for the person who likes to set-up and stay in the one location for days at a time.

Pricing varies from around $350 - $400 online, which in our opinion makes it a great value, dual-battery DIY proposition.

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