Solar Panels - having both fixed and mobile

Thanks CSeaJay for that :-) Now we know what to tell the auto electrician and not feel silly as it can be done! Thanks again!

Again thanks. I was sure it could be done. And that we had seen it in our limited travel. Thanks mazcan

Thank you PeterD. We will print out all this info to take to auto electrician just so he knows :-)

Hi Watson,

The dealer is sort of right, sort of wrong - Yes there must be a controller between solar panels and battery/s. You do NOT need two controllers. A single controller with adequate capacity (at least 10 or 12 amps) should be mounted close to the battery/s and be fed by your 2 panels. This should preferably be a MPPT type of controller. There should be NO controller on either of the panels. Your fixed panel should be wired directly to the input of the controller, and provision made to plug the second panel into that same controller input.

What's a controller? Bit of a long story, but the essential function is to ensure that the battery doesn't get overcharged. MPPT controllers also do some voltage conversion so that they deliver about 20% extra to the batteries. (Other controllers simply waste this energy.) Sometimes controllers are mounted on the panels, but this is not ideal since they need to respond to the state of the battery, not the panels and operate best if close to the battery so any wiring losses are minimised.

If the caravan dealer isn't aware of the above, suggest have the work done elsewhere.

You might find Electricity for Camping a useful read.

Cheers

John

Thanks John and Val.
A bit confused...is a regulator another name for a controller?
If not we would need 2 regulators and one controller?
Sorry if we a bit dim witted but we not so good on technical stuff!
We thought we should let dealer install our 80w solar panel (which just has a small black box connected to the back with a wire hanging out of it) and the regulator (good quality apparently) he will supply to caravan as this will be covered by his warranty.
That seems ok as he has done many.
What is confusing him (the caravan dealer) is the fact we want to also be able to plug in our portable panel to charge the battery via the Anderson plug that when driving would be attached to the car.
We hope you can understand this and help :-)
Steve and Trish

Ahaaa .... the plot thickens!!

I hadn't realised that the Anderson Plug you referred to was actually the one used to connect to the vehicle while travelling to provide some charge from the engine.

This plug is in fact connected directly to the battery. In order to connect a panel to that point it would be necessary to have a controller between there and the mobile panel (i.e, probably on the panel itself.) I think this is probably what your installer is suggesting.

An alternative, which I would favour, is to use a single controller mounted close to the battery to handle both panels, with a direct line from the fixed panel to the input of this controller, and a SECOND Anderson plug allowing the mobile panel to plug into that line running from the fixed panel to the input of the controller.

IF however the controller must be mounted on (or close to) the fixed panel, it may not be possible for the 2 panels to share it. In this case, there may be a case for a second controller at the mobile panel, which could then feed into the anderson plug that's normally copnnected to the vehicle.

re The "good quality" regulator ( controller) proposed - while I'm in favor of good quality gear, the question of MPPT type or other type isn't really a matter of quality. It is a matter of their operating principle. An MPPT controller allows the panel to operate at its optimum, and the battery to be optimally charged. Unfortunately the two optima don't coincide so this type of controller does voltage conversion to match them up.

Hope that makes sense

Cheers

John

Thanks for that info. Problem now solved. The panel we have won't fit atop the caravan. We may get another panel at a later date but meanwhile we will have our 2 x 80s portable! :-)