DC/DC CTEK D250S Dual in D4

Iannicki. I tried feeding a regulated solar supply into my setup like yours and it went all cock-a-hoop. Fortunately I could bypass the solar regulator on the panels. So I say go option 3 as well. Matti

We have a DC/DC in our camper run from the car and while it does work, it doesn't charge the camper battery fully, we charge the battery before we leave home from our 240 charger and the DC/DC charge keeps it topped up while on the move.

Now this is good for the first couple of nights, but if we move to another camp, the DC/DC doesn't seem to re-charge the camper battery fully to the next camp, this was very noticeable after our first camp was 3 days of rain and cloudy weather and what we had to do was break out the inverter and 240 charger to charge the camper battery off the auxiliary battery in the car overnight even after a full days drive, the water pump barely worked we had to use the hand pump on the first night.

So now we just have the USI160 that charges the other two batteries in the car, it now charges the camper battery while on the move, the USI160 allows you to hook up a solar panel if needed also, to be honest I didn't think it would make that much difference, but I was surprised at how much better it is now.

Anyway no need to top up the camper battery now when we get to camp, all good now.

Baz.

Solar regulators often limit the charge to 10 amps. What does the CTek do - 20 amps?
I wouldn't connect a panel with a regulator to a DC-DC. One or the other.
I just have the solar panels with regulators connected directly to the battery on both the camper and Defender. Put the regulator close to the battery if possible.
I do have a DC-DC on the camper, but the solar doesn't go through it, it just compensates for voltage drop from the vehicle.

PWM controller on the solar panel, 3-way Anderson plug, one to car (aux battery and via Traxide controller to start battery) and one to trailer battery. Decent sized cables from aux to trailer = little or no voltage drop. All batteries fully charged within a few hours of leaving camp. (Standard Disco 1 alternator)