During winter months your battery is at the most risk. Sudden high current drains on the battery while it's cold and probably a bit weak can quickly drain it and can even shorten its life. The fact that some cars are stored over long winter periods, or any other time in the year, can mean that the battery becomes drained over that period and won't have enough life in it to start the car. Using a battery charger over a sustained period will damage the battery, so what is needed is a battery conditioner which will charge only when it senses the battery needs it. Maintenance pulse charging increases battery life and can charge even drained batteries. Something like the CTEK XS 0.8 battery conditioner is a very high quality unit which can be connected for months at a time so is ideal for seasonal vehicles. It has a compact design with mounting holes for permanent fixing if required.
Some battery conditioners also have modes which recondition your battery, correcting acid stratification which often occurs in deeply discharged batteries, and restoring the capabilities of the battery and extending its life. Often the battery conditioner can supply a constant current so that when you change a battery you don't lose any settings in your multimedia equipment, which you might otherwise suffer if the power is interrupted. You can even get battery conditioners which measure the temperature of the battery and select the appropriate settings to charge the battery most effectively.