DC - DC Battery Charger. Ctek ???

I have the Arrid twin Charge and it requires a 20 amp supply. It won't function if it can't get the 20 amps. It is an older version and I hear that the newer ones require more, around 30 amps i think.

There is another one made by Redarc I think.

I've been using the Twin Charge for over 5 years with the same battery, it works fine. This is the only charge the Van battery gets.

Hi Scrubby,
There will be others who can perhaps help more on this but, I can't understand why you would want to use a DC to DC charger between solar panels and battery.

Just connect direct from solar regulator to battery. All the available amps will then go to the battery and the purpose of the regulator is to regulate the voltage, same as the DC to DC charger would do.

DC to DC chargers are often used to charge remote batteries, like in a caravan or camper trailer. Their attraction is that they overcome the problem of voltage drop over long cable runs.

While they have advantages, like overcoming voltage drop and acting like a smart charger, they have disadvantages. They don't take advantage of all the available surplus current available from an alternator. Most alternators can put 30 or 40 Amps (or more) into your batteries via a standard dual battery system and heavy enough cable. In my view, you get better and faster charge into depleted batteries with this simple system than with a DC to DC charger.

Where the DC to DC charger gets in front is where cables are too light, distances are very long, and over the last 20% of charge (where the smart charge ability adds value). I know there are some big fans of these devices who may disagree with me, and suggest they are great in all circumstances. I've simply stated the facts as I see them.

Does not really answer your question, but hope it helps.

Norm C

Compare everything in terms of power delivered/consumed and multiply by all power conversion efficiencies.

E.g. panel output 40W, DC/DC efficiency factor 0.85.
Note the panel power is at a maximum only if the panel voltage is allowed to sit at around 17V. I don't know if you can set your DC/DC converter to a fixed input voltage like 17V, in which case the panel's power efficiency factor would be around close to 1.0. In case the DC/DC reduces the voltage on its input to 12V, the panel efficiency factor would be around 0.9
Doing the math with 12V DC/DC input, you're looking at DC/DC output power of 30.6W.
If you use this power to recharge a 12V battery, you'll have about 2.2A of charging current available (30.6W/14V) but only while the sun fully hits the panel in a perpenticular fashion.
Note that the battery itself also has a power conversion efficiency, depending on the chemistry but generally, AGMs are better than wet cells.

Looking at the example above, you can easily find out, how much solar panel power you'd have to provide if you want your DC/DC charger to output 20A.
Divide the 2.2A into the 20A, and multiply by 40W, equals 365W.

Best regards, batterymeister

The big strength in the RedArc (MBS?1215...???)is its ability to accept and control power from various sources (including solar) and fully charge the aux. battery.

I use a RedArc VSR to feed alternator current to the house via a big cable, but I top them up via a solar controller and solar panels.
If the house is very low, the 80A alternator can give them up to 70A of charge, but that drops rapidly as they come ip in voltage, because alternators are constant voltage devises.

Cheers,
Peter
OKA196 Motorhome