Plug-In Solar Panel maintains charge of 12 V vehicle batteries.

Able to maintain up to four 12 V batteries connected in parallel, SP-5 OTR Solar Charger Maintainer harnesses solar power to reverse normal loss of battery power, sulfation buildup, and parasitic draw on erratically used vehicles. This 5 W, commercially rated solar panel, by temporarily attaching to vehicle's exterior hood via 4 suction cups and plugging directly into OBD connector for power, can be installed and removed within seconds.

This story is related to the following:
Electrical Equipment and Systems
Green & Clean

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[source: http://news.thomasnet.com/fullstory/Plug-In-Solar-Panel-maintains-charge-of-12-V-vehicle-batteries-20054177]