School me on DC/DC chargers and systems

[PeeBee]

I run the double units, the 250a and the smart pass. They work well, lot of money though for what they do. They are mounted in the vehicle on the rear cargo barrier. I have had a smart pass fail after 5 yrs though, unsure what the expected life is though.

[Hodge]

Hodge I see you dont run a smartpass I thought they ran as a pair what am I missing.

Smartpass is optional. It just ups the amps and adds a few other functions .
The 250 on its own is just a standalone DC to DC charger.

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[dads tractor]

Thanks for the replies fella's so if I went with just the D250sa into 2 x Aux batteries of say 100 a/hr backed up with a 250 w solar blanket a la kings will it cover me . 2x40lt engels one as freezer one ice cold for beer and 2 camp lights that draw 4a/hr.

All suggestions considered.

[Hodge]

Thanks for the replies fella's so if I went with just the D250sa into 2 x Aux batteries of say 100 a/hr backed up with a 250 w solar blanket a la kings will it cover me . 2x40lt engels one as freezer one ice cold for beer and 2 camp lights that draw 4a/hr.

All suggestions considered.

D250sa is only 20A on paper.

If you can , id be adding the smartpass , since youve got 2 X. 100 ampers there.

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[stevemc181]

I've recently changed from a Redarc BCDC-1225-LV to an Enerdrive END3DC40+ unit for my Lifepo4 battery. It's like chalk and cheese now, can pump 50 amps into the battery no problem. User programmable charge settings. The Redarc was never designed for my Lifepo4, but it's been doing the job for 5 years until I decided a few weeks ago to get the enerdrive unit, it is so much faster to charge the battery now, I'm a happy camper so far.
A 20 amp charger on it's own will take forever to charge 2 x 100a/h batteries.

[Patricapatrol]

I just installed the 250SE into a 97 GQ , so no smart alternator. The sensor (red) according to my interpretation of the fitting instructions you leave disconnected? So how does the unit isolate from the starter battery when ignition is off?

[0-TJ-0]

I just installed the 250SE into a 97 GQ , so no smart alternator. The sensor (red) according to my interpretation of the fitting instructions you leave disconnected? So how does the unit isolate from the starter battery when ignition is off?

Similar to a simple battery isolater it will detect the voltage of the main battery /alternator. It will connect and charge at and above 13.1v and disconnect at and below 12.8v.

The wire for the smart alternator forces the unit to start charging at a lower detected voltage. 11.8v I think the instructions say. So in reality that means it will start charging as soon as power is applied to that red wire.

[Patricapatrol]

So leave red wire disconnected as unit detects starter battery voltage. It is smart. So if I connected to to an Ignition wire it would charge at a lower voltage so I can trick it.
I understand the black wire if connected to earth for AGM battery (solar charge14.7v) and to 12v + if a lithium
Thanks for that , appreciate it 😁

[pollenface]

The Ctek by itself is a great unit, I used a D250S for many years mated to a 100w solar panel. With engine running it would provide a 20amp 5-stage charge to the deep cycle. Without engine running the unit serves as a 3-stage mppt solar charger to the deep cycle and a float charger to the cranking battery. You don't need smartpass, that's just extra complication in my opinion. D250SA is required for smart alternators. While my vehicle was parked in my garage while I was away for work I'd connect an 1.5amp 18v dc power supply to the solar panel input so both batteries were always fully charged.

Personally if I was to buy again I would get a newer 25amp redarc unit as they are compatible with old & new alternators and all types of batteries including Lithium.

[Hodge]

So if I connected to to an Ignition wire it would charge at a lower voltage so I can trick it.

I believe it would still have a voltage cut off... Regardless of what the ignition wire is doing.... I'd have to have a look in the manual to confirm.

Love my Ctek. When it has solar running and the Aux gets to a certain level it trickle charges (backfeeds) the main battery too. At times i've had both batteries more charged at while packing up camp, than it was when I got there.
I have the Smartpass unit sitting in it's box. Don't think I really need it yet as my Aux is only 110AH, the 250sa does the job flawlessly on it's own. It does have other features, but like someone mentioned here, it only adds more wiring and space taken.