On Feb 13, 10:29*am, M.Joshi wrote:
I decided to look at a 10W panel as I assumed this would
produce an adequate output with reduced sunlight in winter.

Not to charge from flat.
Remove the battery from the car, get a battery charger from Ebay / 2nd-
hand shop (£5-10), then charge until about 75-80%.

After reading some of the replies to my original post, I'm not so sure
now?

I just skimmed through and noticed the assumption the car remains
connected to the battery - so the solar panel has to handle the
parasitic drain of the car clock, car radio, car ECU, car alarm, car
immobiliser etc.

If you disconnect the car from the battery the solar panel need only
keep the battery topped up. That is viable. Some here might be able to
tell you the self-discharge of a lead acid battery, and thus whether
you could get away with a 5W panel.

On Ebay & Online there is a simple battery connector where you unscrew
a knurled plug from it to disconnect the battery. No idea how reliable
they are, but it would make disconnect the car from the battery
somewhat spanner-free.