Abstract: A circuit for balancing battery cells includes a plurality of resistors configured in parallel with the battery cells, and a plurality of switches configured in series with the resistors. A control circuit causes the switches to balance the battery cells based on detected voltage of the battery cells and based on past operation of the cells.

Abstract: A battery system monitors the status of a battery and ensures safe conditions under a range of events adversely affecting the safety of the battery cells, the battery pack or enclosure, or a vehicle housing the battery. In response to the safety event, the battery system provides one or more responses to secure the battery, disconnect the battery, extinguish a fire, or maintain a safe temperature. Upon detecting the safety event, the a controller activates the safety device accordingly to ensure safe conditions.

Abstract: A method of providing power to an electronic device in an energy-efficient manner includes transitioning between power states corresponding to charging and discharging a battery. The state of charge of the battery is detected. Upon detecting a high threshold state of charge, an external power source such as an AC-to-DC adapter is disabled, and the battery to provides primary power to the electronic device. Upon a low threshold state of charge, the AC-to-DC adapter is controlled to provide a high current output to charge the battery and provide primary power to the electronic device. The power states, when cycled over time based on the state of the battery, provide for an energy-efficient method of powering the electronic device.