they charge my battery i only use my car once or twice a week now and my battery isnt doing so well with not being run so i decided to buy these 24.99 each dont need sun they trickle charge any 12v battery they come with a batter clamp connection and a cigy lighter connection finnaly wired them up today had to extend the cable though to run from my boot to the lighter plug even today weather was fairly overcast i put my meter on the plug and it was reading 19.24volts didnt wire em straight to the battery because it says you have to disconnect them when the car is running so not to damage them