A battery system for storing electrical power and supplying electrical power to a vehicle is disclosed. The system includes multiple battery packs, each with a plurality of cells. The cells in each battery pack are electrically connected with one another and the multiple battery packs are also electrically connected with one another to combine the total energy output of the cells of the system. The electrical connections between at least some of the cells include a severable feature, whereby the electrical connection is severed locally at the severable feature in response to an impact force that is in excess of a predetermined magnitude and/or an overcurrent/overtemperature condition.