Additional <span class="highlight">solar</span> charging a caravan

My 40amp Redarc can handle 750w more is ok but of no use on peak days just wasted power supply. Check what brand your charger is and search it's max input.
I think it would be better to run all of the panels wired up correctly to the same input side of the charger. If I understand what your saying you would like to try and plug the 160w panel it into the existing Anderson plug that is usually plugged into the car if so that may confuse the charger because your trying to supply power from both sides of the charger if you know what I mean and it will favour one of the so no benefit gained. I may be wrong though.

If the Anderson plug is connected directly to the vans batteries then you need to leave the vehicles mppt charger in place to regulate the voltage.

There may be some interaction between the controllers when the vans batteries approach a high SOC but generally it doesn't cause any major issue.

I have a similar setup except I use portable panels plugged into the cars solar controller.

Hi Tim,

In order to provide sound advice we must understand the how the system is wired (or proposed to be wired); however, some general advice for consideration:

Wiring the panels in series with the existing panels may be feasible if they are of the same rating. In this case you would bypass the MPPT controller. The overall array would be limited to the current of the lowest panel but the theoretical voltage would equal the sum of all the outputs. You would then require one MPPT controller that can handle the input voltage and the current. The charger then regulates the power to meet the needs of the battery - you will need to ensure the input is within the charger's capability.

Wiring the panels in parallel will limit the overall output to the lowest voltage. In this case the MPPT would remain in use. If the panels are not matched in output you will again have an inefficient setup. The issues related to the charger mentioned above still apply.

I trust this gives you a start point. If you provide the specification of the panels, charger etc perhaps a more helpful answer could be provided.

Just a quick comment on supporting solar panels...there is virtue in having them portable, in that you can site them ideally to pick up the sun early and late in the day as well. As for the feed in...I'm no electrotech, but on my van, the builder installed an aux solar jack on the side of the van...it goes direct to the solar controller that looks after the vans two panels. So, my portable 100W panel and the two roof panels all feed just the one controller. Good luck with it all.

Tim, I have a 175litre compressor fridge in my van as well, so the set up is almost the same.

On the roof of the van I have 3x140w solar panels that runs through a Morningstar 30amp PWM controller that feeds the 3x120ah agm batterys within the van.

I have 2x150w solar panels on the canopy of my ute that are wired through a RedArc 40amp dc-dc MPPT charger that feeds 2x120ah agm batterys in the canopy.

The 2 batterys in the ute are hooked up to the 3 batterys in the van via an anderson plug.

Like you, I thought having two regulators and of different types would cause a problem.
I have recently completed a 6 month trip about the place and have had no problems so far.

I believe that hooking them up this way enables you to draw from all batterys, the charging side of it sorts it's self out. It maybe not the most effective way to do it, as I am sure there would be other more complicated ways to do it, but this way has worked fine for me.

Cheers

I was under the impression that all panels had to go through only one solar controller.

-
Hi Tim,

There is some good information above, but I will try to put the complete issue to you.

Solar modules are typically rated as say "12 volts" which indicates the system voltage that they are to be used on. However they actually output higher voltages in operation and the connected controllers regulate the voltage to suit the battery needs.

CONNECTING PANELS IN PARALLEL:
Differing brands and models of solar panels produce differing output voltages so it is necessary to match panels of similar voltage characteristics if they are to be connected in parallel. Modules of significant higher voltage will overcome those of lower voltage such that they will not contribute.
In your case, you would need to determine the specifications of your panels in order to consider this proposition. However, if the panels are properly matched, this is a good method of increasing the harvest. Just ensure that the controller can handle the current.

CONNECTING PANELS IN SERIES:
This is essentially a "chain" and its strength is in the "weakest link". So the maximum power that can be delivered from panels in series is limited to the rating of the lowest module. In your case, the van panels of 300W would be limited by the vehicle-mounted panels of 160W. The voltage has been doubled but the current has been limited so there is no effective gain. The controller would need to be able to accept the increased voltage.
Furthermore, the vehicle battery is then left without a charging source.

CONNECTING THE CONTROLLER OUTPUTS IN PARALLEL:
If the output of the vehicle solar controller were to be isolated from the vehicle battery and then connected in parallel with the van controller there is a likely hood of undesirable interaction between the controllers upsetting the charging process.
The vehicle battery is then left without a charging source.
Not a recommended option.

CONNECTING THE BATTERY BANKS IN PARALLEL:
If the vehicle and van battery banks were simply connected in parallel, each with their own controllers in place then this would possibly be OK as the impedance of the cabling between the two banks would probably overcome any controller interaction issues. But little would be gained overall.

My recommendation is to leave the system as it is. Your proposition would be to complicate the system without benefit. You do say that it currently "seems to work well". If you wish to add more solar collection you would do well to add more panels to the van, either in series or parallel but with careful panel selection and consideration of the controller current capacity.

Incidentally, the "electro battery controller" you refer to is a device to protect the battery from over-discharge and plays no part in the solar charging.