I am finishing off my renovations and am fitting my solar charging system.  At the moment I have a folding portable 140W solar panels and 1(one) 130AH  AGM deep cycle battery.   I want to fit another portable folding 160W panel and if I connect them together, bypassing the MPPT controller that is on the back of both the panels, and install a better quality 30w MPPT controller nearer to the battery ....then through a CTEK 250s DC DC solar battery charger. Would that work OK?............I am getting another 130AH battery very soon so hopefully it should handle both batteries pretty good.

Am I on the right track???   I have been reading a lot on this forum and think this would be good BUT would appreciate some expert advice on this.

Thanks in advance guys........SARG.

Bypassing the panel mounted controllers will be fine, I assume you meant 30 amp not 30w.

You can't successfully feed the output of the MPPT controller into the input of a DCDC charger or the Ctek 250s. 

The reason is that the MPPT controller needs feedback from the battery to determine charge parameters, this won't happen with the Ctek device in the middle.

The Ctek 250S is not a DCDC charger in the accepted sense as it does not have the ability to boost the charge voltage above that of the input as do true DCDC devices.

You may be better to just use the Ctek unit as an MPPT controller and either feed its alternator terminal directly from the crank battery or via a real DCDC device if you want good alternator charging to occur. 

Brian I think you are confusing the D250S Dual and the Smartpass. The Dual is a true DC - DC charger. The Smartpass is used in conjunction with the D250S Dual for the occasions where you over discharge your battery. If you don't flog your battery too hard you may not use it much. The Smartpass bypasses your Dual for the initial time where the alternator is capable of providing more than 20 A into your battery. See this Youtube link

Sarg, you don't need 2 MPPT controllers. If you are aiming at getting a D250S then that will be all you need in the way of an MPPT controller. It has more than enough capacity to handle 300 W of panels.

PeterD wrote:

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Brian I think you are confusing the D250S Dual and the Smartpass. The Dual is a true DC - DC charger. The Smartpass is used in conjunction with the D250S Dual for the occasions where you over discharge your battery. If you don't flog your battery too hard you may not use it much. The Smartpass bypasses your Dual for the initial time where the alternator is capable of providing more than 20 A into your battery. See this Youtube link

Sarg, you don't need 2 MPPT controllers. If you are aiming at getting a D250S then that will be all you need in the way of an MPPT controller. It has more than enough capacity to handle 300 W of panels.

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 I have never seen in any of Ctek's documentation or advertisements where they even claim the D250S dual to be a DCDC charger. Perhaps you can point me to that information.

A DCDC charger needs to be able to take a lower voltage input (say 11v) and provide a higher voltage output suitable for charging the battery, the Ctek, as far as I am aware, and until you show me otherwise, cannot do this.

brian wrote:

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 I have never seen in any of Ctek's documentation or advertisements where they even claim the D250S dual to be a DCDC charger. Perhaps you can point me to that information.

A DCDC charger needs to be able to take a lower voltage input (say 11v) and provide a higher voltage output suitable for charging the battery, the Ctek, as far as I am aware, and until you show me otherwise, cannot do this.

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 There is probably a good reason that Ctek don't use the term DC - DC charger. It's not a term used in Europe and they are a European company. LEAB don't use the term either they use the term either, they call their units "boosters." Sterling (British) have 2 slightly different concepts, An alternator to battery charger and a battery to battery charger.

DC-DC charger seems to be an Oz (and maybe Yankee) term for these chargers. The D250S boosts the alternator voltage (less the voltage drop in the leads) to battery charging voltages. They drop out at an input voltage of around 12.7 V, just like a lot of the other chargers that don't have a separate lead to sense that the engine is running. That way they do not need an isolating device in the tug.

These devices have different design philosophies. They all boost the input voltage. They all charge the batteries with a multi stage operation. They all have DC inputs. They all have DC outputs. If they are not DC - DC chargers then what are they. I don't care if you can not see it, the rest of us can see all these devices as DC - DC chargers.

Sarg,

I know little about the Ctek chargers, but another option for you would be to bypass the controllers on the back of the panels, and to feed both panels into the 30A MPPT you mention, then directly to the battery. No need to go near your Ctek.

MPPT chargers get a little confused when there is another charger charging the same battery at the same time, but I suspect this will not be an issue as it sounds as if your Ctek is charging from the alternator when you are driving, and the panels you mention are folding, thus only likely to be used when stationary.

If both chargers do land up in use at the same time it is not the end of the world, just means the MPPT will not be as efficient as it should be. The MPPT checks the battery voltage and sets its charge voltage just above (typically 0.5V above), this is one of the ways they increase efficiency. Where a traditional charger charges at a set voltage probably 14.2V (depends on battery type selected). If both chargers are working at the same time, the MPPT will see the Ctek voltage and sets its voltage slightly above it, thus wasting power.

plendo  simple answer for us not so elect minded ( LOVE IT)

                                   suenray

Plendo wrote:

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Sarg,

I know little about the Ctek chargers, but another option for you would be to bypass the controllers on the back of the panels, and to feed both panels into the 30A MPPT you mention, then directly to the battery. No need to go near your Ctek.

MPPT chargers get a little confused when there is another charger charging the same battery at the same time, but I suspect this will not be an issue as it sounds as if your Ctek is charging from the alternator when you are driving, and the panels you mention are folding, thus only likely to be used when stationary.

If both chargers do land up in use at the same time it is not the end of the world, just means the MPPT will not be as efficient as it should be. The MPPT checks the battery voltage and sets its charge voltage just above (typically 0.5V above), this is one of the ways they increase efficiency. Where a traditional charger charges at a set voltage probably 14.2V (depends on battery type selected). If both chargers are working at the same time, the MPPT will see the Ctek voltage and sets its voltage slightly above it, thus wasting power.

 

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Hi Plendo

AND both will work happiily together, EACH charging , UNTIL the  changeover from boost voltage battery  is reached

Then funny things may appear to be happening but it is not a problem

PeterQ

HI Brian
The Ctek 250DS IS a DC /DC Charger for use with an alternato & also solar}

Perhaps this will help

http://www.themotorreport.com.au/51965/ctek-d250s-dual-dc-dc-12v-20-amp-5-step-charger

PeterQ

-- Edited by oldtrack123 on Wednesday 8th of January 2014 01:47:44 PM

Gentlemen,

I suspect you both understand the capabilities of the CTEK, and yes it is a DC to DC charger, that is designed to satisfy one of the many types of Dc to DC charging requirements. What it appears to be designed to do is to take a voltage that is above teh battery voltage (example solar or a local alternator) and to control that to provide a managed charging scenario specifically for lead acid batteries.

It does not handle some of the other types of DC to DC charging that some of the other chargers do satisfy, example using a voltage lower that the battery voltage to charge a battery, but there are other examples that can address that, and from what Brian says that need is addressed by the Redarc.

There are many situations where someone will want to use a DC source to charge a DC battery (yes I know all batteries are DC), and there are many valid solution, no specific tool fits all the situations, and no company or vendor has a mortgage on the term DC to DC charger.

brian wrote:

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Plendo, in the context of what you have said, simply connecting the 2 batteries together could be claimed to be a DCDC charger,

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 Can I ask a simple Q...

IF I connect a 24v set of batteries showing 28.2v (House batteries)

to a

24volt set of batteries showing 18.1v (flat start batteries)

with a good set of jumper leads 6B&S will the start batteries come up ????

Just a simple YES/NO answer will do..

Hi Brian,

please see attached adds fro CTEK 250S clearly described as DC to DC, indeed almost every add for the 250S describes it as a DC to DC charger. Anyone standing back and looking at it would understand it takes DC in, applies some logic and supplies DC to charge a battery. 

brian wrote:

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 This is not what a DCDC charger is recognised to be, and I am yet to be shown any Ctek advertising where they actually claim their 250s dual to be a DCDC charger.

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 Why would any European company make any song and dance about claiming their products to be a term not used in Europe? They would be more inclined to use the term booster for their devices. The device has a DC input, a DC output and its output is tailored to charge batteries. What more do you want. Show me an authoritative publication with a definition of DC - DC charger, I that is more important than showing you somewhere where Ctek, Sterling or Leab have used a term that is not in their culture. 

The D250S was designed way back when alternator charging voltages did not drop below 13.5 V. The device and other brands were designed with a higher cut-off to alleviate the use of a dual battery isolator. All those units were referred to as DC - DC chargers back then. Just because alternator technology haws moved on and these devices now have severe limitations with the new alternators does this mean they are no longer what they were designed as.

You make a point of older technology not being suitable for modern vehicles. Even Redarc has current equipment in this class. They now have newer designs that require a signal line to be wired to the ignition circuits of the tug to overcome that limitation.

brian wrote:

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Simple answer....yes and no. More indepth answer... They will come up, but the others will come down. Just how much each does so will depend on the relative capacities of each. Likely outcome is that equilibrium will occur where you have 2 sets of partially charged batteries at the same voltage.

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 Thanks Brian,

That is exactly what I hoped would happen..

I couldn't wait for it to happen and  connected the charger to the start batteries and got them back up that way but it is good to know it would have happened..

I wanted a DC to DC charger, but now I'm really confused!!! lol

Thanks Brian,

I will be happy to leave you in your somewhat delusional world. It does seam strange to me however that everyone else appears to agree about what a DC to DC charger is.

I declare it a draw..lol..

I think you have both educated all of us that are interested and made us aware of the pitfalls in selecting equipment..

I guess it boils down to buyer be aware and you have certainly given us something to think about...

Now come here and shake hands and grab a drink of your choice...

Thanks Guys, I appreciate what you're both saying and where you're coming from. I will certainly do further research.

Juergen,
I wasn't trying to start the motor with those leads just trying to bring the lesser charged batteries up at the expense of the higher charged batteries..

My guess is the transfer rate would be less than 2 to 4 amps maybe even less..

brian wrote:

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PeterQ, with regard to this discussion about the ctek 250s dual. It is generally regarded that a DCDC charger will have the ability to take an unsatisfactorily low incoming supply voltage from an alternator or similar and boost it to a usable level for charging a remote or second battery. It is to be expected that due to voltage drop or other causes, that incoming voltage could be well below 12v. The ctek unit cannot do this. It cannot boost voltages that are below 12.7 volts. It cannot be used in conjunction with the newer alternators that regularly reduce their output below that level under normal operating conditions. Ctek have come up with a partial fix that involves a relay connecting the alternator to the solar MPPT terminal in order to provide a better boost, but this will still only go down to 11.5v. By contrast, the Redarc unit and others can handle inputs as low as 9.6v. My statement that the ctek 250s dual is not a true DCDC charger stands. If anyone requires further information to check the veracity of my post, please feel free to contact Bainbridge technologies directly. You may learn something peterD.

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HI Brian

Well NOW it seems you are changing your story

You now seem to admit that the Ctek is a boost charger but with a 12 8V lower limit ??,WHICH it boost up to 14.5V

BUT you say it is not a true Dc to dc charger just because it has a higher voltage stop charge limit than some later ones on the market like Redarc

IF that is your line of thought, why stop at 9.6V lets go down to 6V ?

It does not start to charge the house batteries until the crank battery reachs 13.4V

I t is  designed to ensure the CRANK battery ALWAYS has at least 12.8 Volts [.fully charged]

Who on earth would  anyone want/ recommend  to wire the charge circuit wth cables so light that one could have INPUT voltages as low as 9.6 volts????

Any Dc line drop  0.5V exceeding [3< 4% ] is excesive in IMHO.yet YOU are suggesting that 25<27% is aceptanble

[Note these figs are based  on SOME  new vehicles regulating @13.2V  I am pretty certain NONE go lower than THAT!]

IF someone asked mE if that sort of  VD was OK

I would very definately say NO

You Have massively undersized cables  /,high resistance connections & are WASTING VALUABLE ENERGY  

GET IT CORRECTED

PeterQ

Remembering that the unit will need to make  up for  the lower voltage input by drawing even higher  currents from the ALTENATOR ,IF IT CAN COPE.

LOSE 3.2V in cable voltage drop, 'ooh yes ,some auto electricians & some sellers will push them as a means of EXPENSIVELY compensasting for inadequate wiring  

280W input  20A/14v  charge current requiring 30A /9.6V input current 

PeterQ  

-- Edited by oldtrack123 on Thursday 9th of January 2014 12:18:12 AM

-- Edited by oldtrack123 on Thursday 9th of January 2014 12:23:30 AM

-- Edited by oldtrack123 on Thursday 9th of January 2014 12:24:44 AM

-- Edited by oldtrack123 on Thursday 9th of January 2014 12:33:33 AM