Solar charging

Can someone advise me please, I've got a flexible plug in 18w solar panel which I stick on my windscreen to keep starter battery topped up while in storage. I've been given another one same sought and was wondering if I could use two in the winter months. On the transit there is a separate 12v plug in , so could use that one. It's just a boost when there's not much sun about in winter months . Many thanks Paul.

Do they both have regulators (either built-in or separate)? If not, you may find that with 36W you are in danger of overcharging the battery when you get full sun on the panels, even in late autumn or early spring.

Paul

I use a 18w charger on my caravan and it easily copes with keeping the battery charged in Winter, so I doubt that you will need 36w so why not use the other one to charge the Hab battery.
With regard to the 12v socket you have I doubt that you will be able to use if it is a factory fit as it will be through the ignition. I bought a motorbike 12v socket and wired this direct to the battery using decent sized cable fused at 10a and screwed this under the dash and we use it for charging the phones as well
David

Thanks for your replies,  will stick to one and may use the other for habitation   battery as advised. Just needed to know, thankyou.

It will depend on the standing current when everything is off.  It might be about 0.1 - 0.2 A.  A panel this size will not help much in the winter especially.  I have a 140W panel (and a regulator of course) which keeps both batteries will topped up except in December and January when even that is not enough.

Thanks for your replies,  my solar panel does have a regulator so I think it would be ok to have 2 going the same time.

Unless you have changed the wiring the cab sockets are only on when the key is turned on.  It is normally the cab battery that needs topping up.  The habitation battery lasts several months if you turn the 12V electric supply off.

Both sockets are live without the key and are standard ford sockets.

paul long wrote:my solar panel does have a regulator so I think it would be ok to have 2 going the same time.

The problem with using 2 panels + regulators onto one battery is that you are likely to find that, due to component tolerances, one regulator will have a slightly higher cutoff voltage than the other. If so, that regulator will tend to inhibit the other one, so you are likely to find that one of the panels is doing most of the work, and the other does very little.

Of course you might get two regulators that happen to be very closely matched - that will be more a matter of luck than anything else...

Yes mojo, the panels and regulators are both same and make.