Model S battery parked with 50 percent charge would approach full discharge only after about 12 months. Model S batteries also have the ability to protect themselves as they approach very low charge levels by going into a “deep sleep” mode that lowers the loss even further. A Model S will not allow its battery to fall below about 5 percent charge. At that point the car can still sit for many months. Of course you can drive a Model S to 0 percent charge, but even in that circumstance, if you plug it in within 30 days, the battery will recover normally.
All cars require a certain amount of attention to perform properly. If you drive a gasoline engine with no oil it will fail completely and need to be replaced. The same happens if you drive without sufficient coolant or a broken fan belt and don’t heed the warning signs displayed by the car. At Tesla, we provide many redundant visual and audible warnings if your battery ever needs attention. And from Roadster 2.0 and beyond, your Tesla can even let us know it needs your attention. If that happens, we simply contact you and suggest you charge your car.