cTek D250s DC – DC Charger / Isolator

CTEK_D250SWhen you do enough outback travel, the bane of your existence will be the black art of 12 volt battery management.  No matter what the product brochures tell you or what is described in the manuals, Murphy is always nearby waiting to pounce and throw you a problem that just defies all logic.  Its for this reason, I have always adopted the KISS principle (Keep It Simple Stupid) when it comes to fitting 12v accessories to my 4WDs.  That said, it is very hard to avoid the temptation to purchase and fit the latest in technology in an effort to make your touring life that much more comfortable.

In a 4WD, a proper dual battery system is absolutely crucial to effective 12 volt power management.  Without it, you could easily be stranded in the outback with a couple of flat batteries and a car fridge full of spoilt food and hot beer.

I have always relied on cTek 240v battery chargers and when it came time to replace the dual battery isolator in the Patrol, I decided to try out the D250s unit.

Now this is not ordinary battery isolator, in fact that is really only a part of this amazing product’s story.  It uses a similar charging circuit to that of their 240v chargers to give a true 7 stage battery charging process from either your alternator or from an external solar panel.  This provides far more effective battery charging than just the straight constant output from your alternator.  It operates as a DC to DC converter of sorts so it can be used quite effectively for charging batteries located in the rear of the vehicle or in a trailer via an Anderson plug connection.

Wiring it up is as simple as it could get with just 4 connections to make, all clearly marked. I wired up the one in the Patrol to accept an external solar panel and also to receive charge from a solar panel mounted on the roof if I ever decided to go that way.

The first thing I noticed following installation was that there appeared to be some additional power to the engine and that the Patrol ran much smoother than it did with the old isolator.  I was initially sceptical about this but after driving for a few weeks and noting improved fuel consumption, it seems the load on the engine with the cTek D250s is significantly less than with the old isolator.  I am not certain that this is a feature of the cTek or if my old alternator was just totally inefficient.  What ever the reason, the result was unexpected and definitely no illusion.

The other thing I noticed was that for the first time, I was able to get the second battery to a state of full charge indicated by the bubble indicator on the battery itself.  Now I know these are not an accurate indication of a battery’s state of charge, but it was the first time this had happened.  Normally I would have to give my batteries a top up charge using a 240v charger from time to time.

Having the ability to connect up a solar panel to maintain charge into the car’s second battery whilst camping is also a great feature especially when running a large car fridge.

A couple of negatives about this unit. Firstly, all the indicator lights are on the unit itself.  If you want to monitor what;’s happening to your batteries from inside the cabin, you will need to rig up a separate volt meter.  Also the unit itself is quite large and finding space for it in the engine bay of many 4wds will be difficult.  I fitted one to a mate’s Hilux but there was no way it would fit into the engine bay of our new Landcruiser.

After using it for a few years now I have also learned that maintenance of your battery connections is vitally important to the successful operation of the cTek D250s.  It doesn’t like tarnished connections and you MUST ensure it has a good earth connection.

All up, despite some of its limitations, the cTek D250s is a very good piece of kit.  4 Westies.