I've owned my car since mid-2005 and have not serviced the battery because the owner's manual told me it was maintenance free. Now I've noticed that the electrolyte level is less than halfway up. Should I just add distilled water to bring the level up & buy a cheap hydrometer to check the specific gravity. Or do I need to check the specific gravity before adding any water? And what should the s.g. be? Is it possible the battery is damaged from low electrolyte level. The battery does good except on one single digit temperature day it seemed weak on first start. How do I determine the manufacture date of the battery. It is a MB Hoppecke battery & has 0322 stamped on it. Would this be 22nd week of 2003? The service history does not mention anything about the battery being replaced? Thanks for suggestions!