Cheap C-Tek 250S DC to DC chargers

[peril Senior Member Find all posts View Profile Close peril]

Thanks for your input, I have read all the above before, nothing new there. The fact I happen to come up with a different solution, or combination of solutions, is my choice. The assumption I don't understand is possibly more due to the complexities I'm simplifying in writing. I'm not here to explain myself or the operation of these units, just offer a cheap price I found.

Thanks for confirming that the D250s will charge better at the top end of the cycle, that is a main requirement for me. Also the solar operation of these units and even the charge algorithm used will be of benefit. They are dirt cheap now, so the benefits you list are useful and affordable.

We have not discussed the Algorithm used, that has an effect on the life of a battery as well. eg. Pulse charge can help charge quicker and not boil the fluids. Yes, I read up on it all as well. Nor have you refereed to my posts on linking the duel battery charge directly to the alternator rather than via the main battery, possibly gaining another 0.5v under high draw charge. (total charge effects no one can confirm until I, or someone else, try it)

I made my own diode, cost me under a $1.00 and some solder, don't need to buy one from Leigh. These can be made dash switchable also, if the user wants that ability.

Basically I'm all good with my understanding of these units thanks and made an appropriate informed decision for my use thanks to the 100s of pages on PP. I talked to people both with, and without these unit. I decided that BOTH have benefits dependent on the use requirements. Good thing is I can 'switch' between modes depending on the battery state in my cunning plan, kinda unique. The jury is out on the direct alternator idea but the rest of the plan is, I think you will agree, of solid grounding.

The last thing I wanted, and expected to have to do, was to 'explain myself' or my planned use for approval. You either want a cheap D250S, or you don't. I wont blame you if it fails to perform so stop worrying about me or my education level.

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Hi peril and I’ll leave the DC/DC info alone but for you info, from memory, your alternator to cranking battery lead is less than a metre long and is 20mm2 ( correct me on these sizes ) so you should have less than a 0.2v drop at your cranking battery with a 100 amp load at the battery.

[peril Senior Member Find all posts View Profile Close peril]

Testing by another member showed 0.5v drop, that's 'tested', not sure of the charge current at the time he may have that also. I deal in aerodynamics, and the calculated vs tested data often differ, for various reality reasons. State at testing time, additional loads and variations in meters, fittings etc.

http://www.pradopoint.com/showthread...r-Output/page5

From what I know this guy is an eletrician with the tools and knowledge to test etc.

The issue here is the uncertain regulation of the second battery, when using direct alternator output. It may gain you 0.5v, it may gain you a very unstable charge voltage where the charge current sensor is the main bus of the man battery.. So this time round I'm more inclined to go with a standard battery install with duel charge path options (VSR + DC/DC).

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Peril,

I'd like to know some detailed info about the pulse charging and the algorithm used, I searched Ctek's website many times looking for detailed specs of how their chargers work and have been unable to find any detailed info.

So far all I have been able to ascertain is that they are a five stage charger, the only stage they specify is the bulk charge which is 14.4V more or less the same as the older or a boosted alternator puts out and the industry standard for the past 100 years or so, nothing new and amazing there.

If there graphs provided in the owners manual are accurate to scale, they pulse charge to start with at 20A, they then bulk charge at 20A, well at least for as long as the battery will accept it. The first pulse charge stage is certainly is not to stop boiling as the following bulk charge is at a continuous 20A.

They absorption charge but no specs given, I believe from other sources that this is at about 15.5V.

And they float charge, again no specs given but one would assume the industry standard of around 13.8V.

And that they pulse charge to maintain the battery at full charge but again no specs given,
this pulse charge is certainly not to stop boiling as it would seem the pulse voltage is the same as the float voltage and batteries are designed to float at 13.8V for the life of the battery, ie very little gassing at 13.8V.

So would be interested to here about this pulse charge aspect you have found that prevents "boiling".

No specs as to any algorithms used by the CPU, would also like to here of the details you have for that.

As for solar, from what I have read the mppt charger built into the Ctek is not very good and you would be better off going for a good quality purpose built unit if you can afford it.

Ctek when asked for specific information usually reply with that is propriety information that we won't release as we don't want our competitors to know.

I have generally found that when a company states they don't want their competitors to know they really mean they don't want their customers to know!

If their competitors really wanted to steal their secrets they would simply purchase a unit and reverse engineer it. The Chinese for instance have gotten so good at reverse engineering these days that if a company such as Intel are having problems with the computer chips and can't work out what the issue is they get a certain Chinese company to reverse engineer the chips and find out what the problem is!

Also you mention prevent boiling the fluids, as you no doubt know the fluids do not boil they gas, also as a matter of interest it is essential in some lead acid batteries that the do gas to some degree to mix the acid and prevent stratification occurring in the acid layers.

Looking forward to learning some detailed info on the 250,

Cheers
Leigh

[peril Senior Member Find all posts View Profile Close peril]

That's a good question set there Leigh, not sure there is anything I can teach in specifics to the Ctek that would be of benefit, because like you I used the web as my library. My searches have not found a graph specific to the D250s, so reference to algorithm is limited to other Ctek types as an example of their way of doing this. It seems reasonable to expect a similar approach to charging to be used and not reinvent the wheel.

As for the pulse charge limiting overcharge boiling, like you I would need to search for that reference again. The logic involved in this is based on achieving short burst of high voltage, limiting the potential for overheating. I'm not even sure if this was a reference in a ctek document or some other reading on a similar charger. Likely it was some other unit as I have been reading up on fast charging for many years. I severely doubt it is specific to Ctek, and likely you do know of other company chargers using this?

Thanks for your interest, I'm not here to teach anyone anything about Ctek and don't profess to do so. If Ctek don't list this stuff readily, then reading into the reasons why is purely guesswork. How about we test it and stop guessing

They cost $220.00 at the link above if you want one.

[winniliss Avid PP Poster! Find all posts View Profile Close winniliss]

They cost $220.00 at the link above if you want one.

Thats $209 for the above link :-D

I am yet to do real life testing with my system (D27F for aux and full river in the camper trailer, run them down and see how long they take to charge). It will happen worst cast Aug next year but it will happen.

In relation to what people use, it's up to the people to decide once given all the info. If they one product over another so be it. It's not our money Ralf...

Winston.