Bosch SKC181-02 18-Volt Lithium-Ion Starter Kit with (2) 2.0 Ah Batteries and Charger Battery pack design protects the battery and tool; resulting in optimal battery life and performance and 35-Percent more run time Optimized cold weather performance, down to -4 degrees Farenheit/-20 degrees Celcius Cool Pack Technology - Innovative pack design dissipates heat for 2x recharge life Electronic cell protection - prevents cells from overheating, overloading and deep discharging Battery fuel gauge takes the guesswork out of when you need to charge