Buy a Solar Power Battery Maintainer to Charge 12 V Battery?

Are you talking in terms of increasing fuel economy? If so, then no, it would be so negligible that you wouldn't notice it.

 

If it is to maintain the 12v battery when not in use they will work well and extend the time storing or parking the car for greater than a week or more without worry of the battery going dead. But it is my understanding that they will not charge the 12v battery by plugging into the Cig Liter or the Acc Charge Port with out a modification. So you also either need to add the jumper to the fuse box or wire directly to the battery.

See this link , go to services modifications
www.lusciousgarage.com/

 

The only time I would have such a need is when I leave my car at the airport for a couple of weeks. However, I would be afraid of some idiot reporting a suspicious looking solar panel on my dash board and calling in the SWAT team and Bomb Squad and dismentle my car when I am gone. This day and age...

 

There are solar chargers made that charge through the OBDII port.

 

Yep. I got free one from a VW dealer. I posted about my search for a solar maintainer and how I got a free one at solar chargers? VW OBD2 port chargers? OBD2 disconnect/reconnect cycles? | PriusChat.

 

If you leave these on too long can it actually damage the battery?

 

I've kept it in cars that I don't use for weeks at a time and never had a problem.