Solar Car Battery Charger

[Macski]

I have taken my MR2 off road for the winter and looking at buying a solar panel to keep the battery topped up. I was about to get a 5W unit when reading through the reviews it was suggested it is not powerful enough to do the job because of short winter nights. Anyone know anything about the subject and advice would be appreciated!

Also could I connect a 12V panel to a 24V mobility scooter?

Thanks for any replies!

[GreenV8S]

If you have the option, it would be better to remove the battery and put it indoors with a mains powered battery maintainer. If you need to keep it powered up for insurance purposes, just rotate batteries every couple of weeks. The solar route is probably going to need a much bigger panel than you'd think. Is the panel you're looking at designed to maintain 12V batteries? If not you might end up with conversion and regulation hardware which will increase the cost and power requirements from the solar panels. These small panels won't achieve anything like their claimed power output under realistic conditions and by the time you account for short days and low sun you might only average a fraction of their claimed output. I'm sure there are solar panel planning sites where you can get realistic figures if you're determined to go that route.