CTEK D250S dual battery set up

[Timofeevich]

Question to those who are the experts in CTEK D250S configurations :
Would the CTEK setup consisting of 2 x D250S, Smartpass and Charger MSX25 be able to handle the Starter Battery Bank of total 420Ah (12V), the Service Battery Bank of total 480Ah (12V) and TWO Solar Panels of 250W (12V), each connected to its dedicated D250S ?
The diagram is attached below.
Thanks a lot for any thoughts, comments and advise.

 

[dwh]

Nice diagram.

Looks feasible at a quick glance, but wouldn't the smartpass still be limiting the alternator max charge current to 80a?

 

[DiploStrat]

Short Answer ...

Question to those who are the experts in CTEK D250S configurations :
Would the CTEK setup consisting of 2 x D250S, Smartpass and Charger MSX25 be able to handle the Starter Battery Bank of total 420Ah (12V), the Service Battery Bank of total 480Ah (12V) and TWO Solar Panels of 250W (12V), each connected to its dedicated D250S ?
The diagram is attached below.
Thanks a lot for any thoughts, comments and advise.

I don't know - I don't use the CTEK. But I did spend a lot of time with a Sterling A2B, which does many of the same things, and can offer this:

-- Friend of mine did use a pair of Sterling B2B on his Unimog. It worked, as always, the limiting factor was the rising voltage of his AGM battery bank.

-- A SmartPass is limited to 80A by the size of its relay contacts.

-- A pair of S250S probably won't be any faster than a SmartPass/D250S combo. Why? Because at the start of the charge cycle, when the SmartPass relay is closed, the difference between the charge source voltage, even a low 13.Xv and the battery voltage, call it 12.5v is great enough to assure a fast charge. The D250S only kicks in when the amp flow drops to below 20A, at which point the SmartPass opens the relay and the D250S completes the charge. At that point, the D250S contributes its 14.4v, precisely when the higher voltage is needed to complete the absorb stage.

-- The only advantage that I can see to using a pair of D250S would be to connect more solar, and, as I have read reports that the D250S is not a great solar controller, you would probably be better off simply attaching all of your solar panels to a better solar controller, e.g. Morning Star or Blue Sky, or other.

As always, this assumes that you have wired everything correctly, and, I defer to the observations of others who may have actually tried some of this.

 

[Timofeevich]

Thanks for your inputs !
Yes, the 'SmartPass' is limited to 80A and 'SmartPass 120' is limited to 120Ah, but that's not my biggest concern.
The manual for both M300 and MXS25 (Multi XS 25000) says that they both are designed for handling the Battery capacity of 40–500Ah.
Also, 'SmartPass 80' and 'SmartPass 120' can handle 28–800Ah, while D250S works with Battery Capacity of 40–300Ah.
My total Battery Bank capacity is 900Ah, which is above the said limits, but it's been split up for Starter Battery (480Ah) and Service Battery (420Ah), which is below the limit of 500Ah (Smartpass and MXS25), but above the limit of 300Ah (D250S).
So, the question is whether subject setup (that includes two of D250S, Smartpass and MXS25) would handle Two Battery Banks of total capacity 900Ah, while each of the Battery Bank is not exceeding 500Ah.
Thanks s lot !

 

[dwh]

Those battery bank capacity numbers are actually irrelevant. They are not "limits", they are "recommendations". Any charger can charge any size battery bank. The charger works the same no matter if hooked up to a 10ah battery or a 10Kah battery.

The question is if the charger has the amperage capacity to recharge the battery in a timely fashion.

What CTEK is saying with those numbers, is that their equipment is too small to get the job done in a reasonable time if the bank is too big.

Also, the engine bank size is completely irrelevant - it is "upstream" of the CTEK gear. From what I understand, the 250s will pulse/trickle a bit of solar current to the engine bank once the house bank is charged. I wouldn't count on it to do a good job of charging a large engine bank that is regularly drawn down.

And if the engine bank is only used to start the truck and service the chassis loads (as it should be), and not used to service house loads, then it will be fully charged all the time anyway (from the alternator), and providing a way to charge it, say from solar or shore power, is nice to have, but not actually necessary.


My recommendation would be to go with something like the Blue Sea 500a dual sensing ACR, to get the max bulk amps available from the alternator to the house battery to bulk up the house battery in the shortest time (absorb charging will still take many hours no matter what you use).

Hook the 500w of solar to the house battery with some top quality MPPT charge controller - Midnite, Morningstar, Victron etc.

Then buy the biggest shore charger you can provide power for and connect it to the house bank. For instance, a 90a Iota with IQ/4, a pair of 60a Xantrex TrueCharge 2s, a Xantrex Prosine 2.0 inverter/charger (100a charge current to a 12v bank).

(Of course if you are planning to use a small generator like a Honda eu2000i, you might only be able to power a 45a-55a charger.)


Getting the house bank bulked up quickly is the key issue to be considered. Hours of absorb charging is still hours of absorb charging no matter what you do. Keeping the chassis bank regulary topped off from solar or shore power is just a nice side benefit and the ACR will provide that - AFTER the house bank is bulked up.

 

[Timofeevich]

dwh, thanks a lot !

 

[DiploStrat]

dwh Hit Most of the High Points

I would add:

-- The first thing you need to know is the normal output voltage of your vehicle's charing system. Most US pickups and SUV's run at well over 14v, making most voltage boosting products unnecessary. Some Toyotas run at 13.9v and I have heard that Sprinters have lower charging voltages.

-- For lead acid batteries, high voltage, at the absorb stage, is very important for battery life. So if your vehicle runs at less than 14v, you are probably in the market for some form of voltage boosting technology, whether it be a B2B or simply increasing the voltage of your charging system. (There are many ways to do this.)

If you vehicle runs at over 14v, then you are probably in the market for a relay based system - either ignition controlled or voltage sensing or "intelligent." Or, if you trust your memory, you can use a big dumb switch. If you choose to go with a B2B, then it appears that CTEK has a new model D250AS, which is designed to deal with "smart" alternators and an uprated Smartness 120, which can handle higher amperages.

Finally, the whole reason for fooling with a battery isolation system is not "to be sure that I can still start my truck in the morning." If you are running your battery down that far every night then your battery is too small and it doesn't really matter what kind of isolator you use, you are going to see poor performance.

Let that last one sink in a bit. Many people agonizing over isolated battery systems are doing it wrong and for the wrong reasons.

 

[Timofeevich]

DiploStrat, many thanks for your comprehensive reply !

 

[DiploStrat]

DiploStrat, many thanks for your comprehensive reply !

My pleasure. Go to my website for many documents and slide shows on this subject.