I have a low mileage C5 convertible for which I have just bought a ctek trickle charger. In the past the car was stored for 6 mths with no battery support. It would have to be boosted and then charged at the beginning of each season. The car will be stored in an unheated garage in Toronto winter cold. How does the trickle charger work? Can it be left connected for the entire 6 mths? Is that safe for the battery/car/garage?