A battery pack with a first battery and a second battery, wherein each battery is a plurality of cells connected in series, and operable in a storage mode and a use mode, a storage mode defined by isolating the first battery from the second battery, and a use mode defined by electrically connecting the first battery to the second battery. The storage mode may include: electrically isolating said first plurality of cells from said second plurality of cells or physically isolating said first plurality of cells from said second plurality of cells.