must battery systems be expensive and difficult?

paul, after reading your post I have had a look for this product to try to see exactly what it does. All I can get is nice glossy brochures saying you connect it and you beaty. Maybe if you have experience with it you wouldn't mind telling me how it does the job? Would it work on 240ah in the camper trailer?

Spade the Ctek D250S is the only method to charge a battery in a caravan or camper trailer properly and as close to 100% capacity. Direct cable charging is useless and does not work regardless of the size cable you use. You need a device like the D250S to raise the voltage and operates like a 240V mains charger, but is powered from your vehicle alternator instead of 240V mains.
Direct cable charging at best may give you 60% capacity charge which is useless. The reason they make these DC to DC chargers is because they work and do the job properly. Half charged batteries from a direct cable system are useless and wreck your batteries

240Ah is excessive battery capacity for a camper trailer and excessive for a 20A battery charger to charge. 150A is max for a 20A battery charger.

Paul,
where do you get your information:
"Direct cable charging at best may give you 60% capacity charge which is useless" ??

Maîneÿ . . .

240 ah gives me four days in mild weather so suits me fine.
I am about to rig some cable for charging while driving hence my interest in the Ctek D250S. This will give me an extra day if I can charge on the way to ............ and a bit of a run from the alterator while camped could give a little top up if I wanted an extra day also.

The spec for the Ctek D250S in the brochure says 40 - 500 ah. I would have thought a 20 amp AC powered charger would be quite ample for 240ah so why would a DC powered one not do the job? (Even 15 amp surely would be sufficient to charge my set up)

If you want to fully recharge your battery in an average days driving then 150Ah would be around the max to 100% recharge.
The great thing with the Ctek D250S if you want to add a solar panel you use the D250S as the solar regulator. The D250S is MPPT which is the best form of solar regulator you can get as it gives you up to 25% greater output from the solar panel.
Technically impossible to recharge a second battery and definitely not at a distance with direct cable. Your 240Ah of batteries would be constantly at half capacity even after 12hrs driving. Quickest way to ruin good batteries. The cost of a Ctek D250S will be saved in the life of your first set of batteries.

paul, I don't expect or really need to get 100% from alternator whether via a charger system or otherwise. If the charger can get me to say 85% - 90% from 40% - 50% in a few hours (maybe a couple of hours) driving then getting the remaining 15% will either happen or not depending on the length of drive.

I certainly want the batteries to be sitting above 80% when I arrive on site but 100% is not really necessary.

I am prepared to spend that sort of money if it will do what I am looking for.

Paul,
I think you should be advising all the companies, both big and small that have put out there in cyberland all the Voltage drop calculators that you are correct and they are all wrong :-(


With 7 meters of 2B&S cable (32mm²) you can realistically expect O.O5 volt drop at the auxiliary battery, so if alternator is putting out a realistic 14.20v the battery will be charged @ 14.15v which is more way than the 60% claimed, more like ~100%.

Forgetting all the voltage drop calculators, I've actually tested my dual battery system which is connected with 2B&S (32mm²) cable and have proven to various people on many occasions the larger capacity cables will give virtually NIL voltage drop.

When 14.4v is charging the cranking battery, ~14.4v is charging the AGM's.
This is definitely not possible with the skinny 6B&S cable you advocate using.

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What your not factoring into your equations is the battery system is not ‘flat’ anyway, it's just down that amount, a small percentage of total capacity, used by the accessories over night, which is not a lot at all comparative to being fully charged, then the vehicle is driven next day it will easily replace what was drawn from it overnight.

You say: "240Ah is excessive battery capacity for a camper trailer and excessive for a 20A battery charger to charge. 150A is max for a 20A battery charger"

What has "150A is max for a 20A battery charger" got to do with anything at all, it does not even make any sence as 20A is max for a 20A battery charger.

Just because his battery bank is beyond, as you claim, the capacity of a 20Amp battery charger does not make it excessive battery capacity.
It makes it very realistic battery capacity, and very suitable to charge by direct cable, of the correct thickness, and I assure you it will charge to 100% for a whole lot less money that what you are recommending.

As to your reference to “snake oil salesmen” I think it maybe a case of the pot calling the kettle a darker color.....

Maîneÿ . . .

I will leave you children to play in the sand pit.

Paul,

this IS your "sand pit"

You must remember it was you who created the "sand pit"

If the information gets too hard for you to answer then ok "leave"

Maîneÿ . . .