Embodiments described herein provide a method for wireless power transmission of reconfigurable power levels. A wireless power receiver is used to receive power from a wireless power transmitter according to a negotiated power level. The wireless power receiver determines whether a re-negotiation condition is met at the wireless power receiver. The wireless power receiver then sends, to the wireless power transmitter, a re-negotiation request for an updated power level different from the negotiated power level. The wireless power receiver receives, from the wireless power transmitter, an acknowledgement that acknowledges the updated power level, and then operates to receive power from the wireless power transmitter according to the updated power level.

A battery pack, a method of heating a battery cell and an electrical combination. The battery pack may include a housing; a battery cell; a heating element operable to provide heat to the battery cell; a temperature sensing device operable to sense a temperature of an interior of the battery pack; a heating switch operable to control whether power is provided to the heating element; and an electronic processor configured to receive a signal from the temperature sensing device, the signal indicating the temperature of the interior of the battery pack, determine that the temperature of the interior of the battery pack is less than a predetermined temperature threshold, and in response to determining that the temperature of the interior of the battery pack is less than the predetermined temperature threshold, close the heating switch to provide power to the heating element.

Embodiments of the present invention are directed to a cell protection system that may be employed in high voltage systems such as grid scale energy storage systems. In some embodiments, the advanced cell protection system includes a proactive balancing system for balancing one or more battery units of the energy storage systems. In some embodiments, the advanced cell protection system includes a switching protection system for safely connecting and disconnecting the one or more battery units of the energy storage systems to other systems. In some embodiments, the advanced cell protection system includes an isolated communication system for allowing the one or more battery units to safely communicate with each other and at least one controller of the energy storage system.