The Wagan Solar Power Battery Charger provides a trickle of energy that will keep your car battery topped-off with enough power to start your car -- as long as you drive it every 24-hours. Depending on what type of problem is causing your battery to drain when the engine is off, you will still have to drive your car regularly to fully re-charge the battery. In my experience, the trouble lights on my dashboard will not turn off, ever. That small amount of energy drain was enough to leave me with a battery too weak to turn the engine over. After a jump-start and a 40-minute drive, I put the Wagan Charger on my dash, parked the car in a position where it would get the maximum amount of sunlight during the day, and plugged the charger into my car's power outlet (the old "cigarette lighter" outlet.) When I went out to start my car the next day, the Charger's red LED light was blinking, and the car started with no problem. I discovered, however, that I needed to take my car for a spin AT LEAST ONCE EVERY 24-HOURS, or the battery would drain away. I skipped one day of driving, and my battery was stone-cold dead the following day.