All Subaru vehicles are equipped with maintenance-free batteries. The term "maintenance-free" can be misleading - as these batteries do require some attention to maintain their cleanliness and efficiency.
Your car's battery is the heart of its electrical system and the chief cause of winter weather start-up woes. In cold weather, the battery loses about half its strength while the demands on the battery increase. Low temperatures reduce the battery's engine-cranking power, and by thickening the engine oil, they also make it more difficult for your engine to turn over. Cold fuel doesn't vaporize well, which adds to the difficulty.
It is extremely important to have your car's battery checked by a Subaru-trained technician regularly. A battery check will include an examination of cable connections for cleanliness and tightness. Loose or corroded connections can dramatically diminish your car's starting power; and if the connections grow loose or crusty enough, they can shut off your car's electrical flow entirely and leave you thinking you have a dead battery.
Low temperatures also reduce the efficiency at which a battery is recharged.
Winter driving conditions frequently require the use of lights, defrosters and wipers for extended periods while driving at slow speeds. This additional load requires the charging system to work properly so that it sufficiently charges the battery the next time you start your car's engine. For this reason, your service technician should also check your battery's charging system and voltage regulator, and inspect your vehicle's alternator to ensure that all components are operating properly.