level. The minimum SoC varies depending on operating conditions. When the car needs more power, such as in mountain mode, the lower limit of the SoC rises to 45% to ensure enough power is available. The battery capacity was increased to 16.5kWh for the 2013 model year, the SOC window was increased to use 10.8kWh of the total battery energy, and the buffer to ensure battery life is not reduced. These changes increases the Volt's all-electric range, but charging takes slightly longer. GM achieved the improved battery performance and durability through minor changes to the material composition of the battery cell chemistry. Despite containing near identical energy (±0.5kWh), the Volt's battery pack is over 70% lighter than the EV1's original 16.5kWh AC Delco lead-acid battery pack, mainly because the Volt uses higher specific energy Li-ion batteries. Li-ion batteries are expected to become less expensive as economies of scale take effect. Because batteries are sensitive to temperature changes, the Volt has a thermal management system to monitor and maintain the battery cell temperature for optimum performance and durability. The Volt's battery pack provides reliable operation, when plugged in, at cell temperatures as low as and as high as . The Volt features a battery pack that can be both warmed or cooled. In cold weather, the car electrically heats the battery coolant during charging or operation to provide full power capability. In hot weather, the car can use its air conditioner to cool the battery coolant to prevent over-temperature damage. General Motors guarantees the Volt's battery for eight years or , and cover all 161 battery components. GM estimates that Volt batteries will degrade by 1030% after 8 years or 100,000 miles. GM has applied for a patent that may allow technicians to quickly and cheaply recover some of the performance of degraded battery packs. The Volt's battery management system runs more than 500 diagnostics at 10 times per second, allowing it to keep track of the Volt's battery pack in real-time, 85% of which ensure the battery pack is operating safely and 15% monitor battery performance and life. The Volt uses the J1772 charging plug, a standard connector for electric cars in North America. Depending on in-car settings, a full charge takes from approximately 10 hours (with the 12A setting) to as much as 14 hours (8A setting) from a standard North American 120V receptacle. From a 240V source, a