Thread: DC/DC CTEK D250S Dual in D4

And I can only refer to two heads of elec eng science in two separate universities that I questioned the last time this discussion arose and wondered why anyone would want a DC/DC when you want to regain available charge asap not withstanding the costs. Not one app where I'm studying uses a DC/DC source for anything (quoted from Professor of Elec Eng and Digital Sciences).

Thats why I use Tim's products. That and his outstanding service.

Well, what a mess!!!

First of all, I thank the responses of some and others. When I win the lottery, I will travel to Austraia and I have a few beers with you, do not argue over that life is short and expensive gasoline (at least in Spain)

Drivesafe know the system and is one of the options I have in mind, provides quick loading, installing plug and play, and many users that support its operation. But I also wanted to consider other options such as DC / DC. Who have incomveniente loading slower, true, but also offer greater control of the load can be beneficial .... another option to consider. I wanted to know if the latter option works in the D4 and new electronics, so simple. I understand that plug negative ground and the negative terminal of the main battery, yes, work (not going to break anything).

Drivesafe: Regarding the D34 optimal battery is no longer sold in Spain, now sells the yellow top 4.2 (I know several users that have mounted D3 through a projectaDBC100k and everything is correct).

Roverlander: Enjoy beer. And a question: To change the negative connection, will the main battery voltage (the boot) will reach higher levels of stress or low values ​​still? And now the auxiliary battery charge when you go to higher gear (accelerating)?

roamer: CTEK D250S it is dual. Yes lets you connect two different sources, alternator and solar bale without an additional unit, although you can add SmartPass. ... I understand that watching your manual.


Cheers to all!!!!

Originally Posted by RoverLander

So glad I'm not saying anything on this... just sitting back enjoying a cold beer from my 12V fridge, running on my two extra batteries that are charged by my expensive and effective DC / DC charger.

It’s this sort of comment that has me amused when ever there is anything mentioned about DC-DC devices.

So you say it’s effective, and is this based on you testing your set up with and without using the DC-DC device?

On another forum I got into an argument with a guy who had just bought a DC-DC device and reckoned it was the ants pants and it did a better job of charging his two house batteries than his alternator could ever do by itself.

A couple of months later and to the guy’s credit, he came back from a trip, where curiosity had got the best of him and he tested his set up with and without the DC-DC device.

What he found when ever he had used a fair bit of house battery capacity at one camp site and then charged by either system while moving to the next camp site was, that even when he drove for a good few hours between sites, he still never managed to fully charge his house batteries by either set up, but they always seemed to be in a higher state of charge when letting his alternator do the job.

He still uses his DC-DC device but just for topping up his batteries.

His comments are that while he got a decent charge when using a DC-DC device, he would never waste his money on another one because, IN HIS CASE ( and it won’t be the same for everybody ) his alternator did just as well or better.

I can only report on what I own and have tested.

Install #1. Installed by myself last year; Car (L322) and camper with the house batteries located in the camper controlled by a basic solenoid switch by ignition. (Solenoid was used so a small winch could operate from the same Andersen plug). The camper also has a Ctec MSX10 batter charger with the same multistage charging as the DC-DC device listed above. I have solar to charge while at camp. Journey home is always in the morning, so the house batteries are usually only down by one nights running of fridge, water pump and lights. When I get home the trailer is connected to the grid, enabling the Ctec to do its thing – according to the doco it charges to 14.4V then goes to an “Analyse” stage (when the battery is fully charged) for 3 min and then “Float” stage. This has always happened in less than 2 minutes of being connected, most times less. At this point the little indicator lamp claiming 100% charge is also on.
So the Ctec device is happy that the battery is fully charged after a 2-3 hours on the Alternator.

Install #2. Installed by factory in 2005 on a Boat; 520ah of house batteries charged by a 2 BEP VSR (simple voltage sensitive relays that connect at 13.8v and disconnect at 12.8v) between house bank and the 2 small start batteries (one for each engine). Engines (pair of Volvo MD2040 40hp diesels) have 60amp alternators on each, there is 3 x 130w of solar and a grid connect 40amp smart charger (Xantrex). House batteries are drained by elec toilets, water pump, fridge/freezer, TV for the footy / F1 / kids movies, lights, auto pilot and nav ect instruments – so they get some use.
If we are out for an extended time and the weather is fine / sunny then the solar can cover everything, and the solar regulator will drop out most days, so engine input is relatively minor if they are started. Again most outings we choose to return home in the morning of the last day and the house bank is well used, if the wind is favourable engines are not used except for berthing and on these occasions the grid charger can take up to 2 - 3 hrs to reach its float stage, up to 7 - 10 if we sailed and haven’t had much sun for a few days. It there the wind gods are unkind, an engine will be run for 1-3 hours plus, on these occasions the charger will start to float with in 5-30 mins depending on how far the engine was run and if 1 or 2 engines were used for that time. The 60amp alternators are original. We have never had a charging issue with standard alternators and experience the same result as the newer camper installation, according to the smart charger the batteries are well charged.

I have nothing to do with Drivesafe, and would not install his product in a boat because of the lower cutout voltage (generally boats have much bigger house banks than the start batt), however I would use for a duel batt in the car for this same feature (and smaller house batt than start batt). As noted I have purchased and use CTec products. Personally I think the DC-DC converters are definitely not needed – I’m not saying they don’t work.

Originally Posted by drivesafe

He still uses his DC-DC device but just for topping up his batteries.

Reading the D250S Dual/Smartpass documentation it appears that when using the two units in combination the D250S is used for primarily charging from Solar panels or other external sources and top up charging from the alternator.

The Smartpass charges at up to 100A and appears to be directly connecting the alternator to the service battery to achieve this. CTEK indicate that the Smartpass can be used standalone, which would suggest CTEK don't see any issues with direct alternator to battery charging.

Hi OffTrack, I actually experimented with this type of operation some 3 or 4 years ago.

One of my suppliers is an importer of high end battery chargers and high current DC-DC converters.

One of the units they have is a USA made 40 DC-DC converters, but even using this unit and having the hand over from direct alternator - battery charging to alternator-DC-DC converters-battery charging, take place at a much higher current available than is available from the toys they sell here, there was just no justification for the high set-up costs when far cheaper and better set ups were/are available. Note, the 40 amp unit is not much dearer than the 20 amp units sold here.

There is a single controlling factor when ever you charge auxiliary/house batteries while on the move, and this just how long you are actually on the move for!

As I have stated repeatedly and as Harlie commented, no one has posted that these things don’t work, the problem is the misleading way they are marketed, leads unsuspecting people to think these devices will out perform alternators when ever you fit one these devices.

This is just not the case and a perfect example of how deliberately misleading advertising hype can be used to make these devices look like the are the end all for battery charging is an article that appeared in the Wanderer magazine a few months back.

This was an article ( actually it was nothing more than an infomercial discussed as an article ), written by one of Wilbur’s hero’s, Collyn Rivers.

The article was out to heap greatness of these devices and listed all manor of wonderful things about them.

One of the treasurers that Collyn Rivers used to imply these devices were better than alternators was some data from Ranox, where they had a graph showing how their 25 amp DC-DC converters could charge two 100Ah batteries from 75% SoC quicker than an alternator could.

The graph shows how the two batteries are charged is 150 minutes using their DC-DC device, while the alternator took 180 minutes.

I have no argument with the data in the graph and would say it was probably spot on the money.

The problem is that most people would be lead to believe these devices will charge their two 100Ah batteries quicker than an alternator could and in reality, as long as they never discharged their two 100Ah batteries below 75% this would be the case.

But if someone had all the facts presented, the first thing that should jump at you from their data is WHY THE HELL WOULD YOU HAVE TWO 100Ah BATTERIES IN THE FIRST PLACE.

If you never discharged your two 110Ah batteries below 75% then a single 100Ah battery will easily meet your needs and you still won’t need to cycle it below 50% SoC and this is a safe discharge level for ANY battery.

The reason the graph started at 75% SoC is because if it went just 5% lower, to 70% SoC, you could literally flip a coin to determine which would set up charge the two batteries quick.

If you discharged the same batteries down to 60% you would have at least a 20 minute advantage when using your alternator, at 50% SoC, you would be at least 1 hour better off when using just your alternator.

At 40% you would be getting close to 2 hours better off, at 30% the gain is better than 3 hours and at 20%, the lowest level you can safely take deep cycle batteries, you would be 4 to 5 hours better off using your alternator than using their 25 amp DC-DC converter.

But what the hell, why let something as trivial as the truth get in the way of potential sales!

BTW, if you re-read Harlie’s thread, he is confirming this very point and based on actual use.

Sorry for the thread dig here team. I understand many of the points raised here and for the most part I have adhered to them in terms of never having bothered to run a DC-DC charger. However, I was due to replace the solar controller in my Jayco van as it was playing up. One Ebay PREWINTER sale later and I have a C-Tek D250SA for $280 which not only does solar as well as DC-DC but has a second set of wires that are used to change the trigger point input voltage at which the DC-DC section starts working due to the lower operating voltage that the D4 can experience when running low loads with a fully charged start battery. Read smart alternator function.

I have not run a second battery in the vehicle but have run heavy guage cable to the rear of the vehicle with a 100A Anderson plug. At the moment that it connected to the battery and the earth mounting point on the vehicle as mentioned in one of the stickies. I trust that this is acceptable or should I be running it directly from the alternator? From the manual I understand that the requirement is for the trigger wire to be connected to an ignition power supply from the vehicle such that it uses a wider input voltage to charge as well as isolates the start battery when the ignition is turned off. I have not had much luck in confirming this from the C-Tek manual or website so any input would be greatly appreciated.

Kind Regards
Paul Nelson

And here's a different question.

I already have the CTEK D250S in my D4 (it was just what the installer used, and a few years before reading this thread). It can act as a MPPT controller for, as I understand it, unregulated solar panels.

I have just bought a 160w folding solar panel kit by Rich Solar. The PWM controller is hard wired and would be difficult to bypass.

So, which way should I go:

1. connect the solar panel to the CTEK unit (meaning Solar Panel, PWM Controller, MPPT Controller, Dual Batteries (noting the CTEK will charge the auxiliary battery first, then the starter battery))

2. connect the solar panel to the auxiliary battery (meaning Solar Panel, PWM Controller, Auxiliary Battery (only))

3. bite the bullet, cut the wires between the solar panel and PWM controller and then conenct the (now unregulated) solar panel to the CTEK unit (meaning (unregulated) Solar Panel, MPPT Controller, Dual Batteries)

Option 1 seems preferable, but only if having a PWM controller and then a MPPT controller in series would actually work.

Grateful for the replies of anyone who knows whether having two different types of controller in series is a good or bad idea.