Battery electric system with alternating current self-heating mode

A vehicle, comprising:

• a vehicle body;
• and
• a battery electric system connected to the vehicle body and comprising:
• a direct current (DC) voltage bus;
• a battery pack;
• an inverter connected to the DC voltage bus and having a plurality of solid-state power switches;
• a transformer having a primary winding and a secondary winding;
• a capacitor connected in parallel with the battery pack;
• a first electrical switch connected between the inverter and the battery pack, the first electrical switch being configured to close during an alternating current (AC) self-heating mode of the battery pack, wherein the AC self-heating mode includes generating an AC waveform through the battery pack at a controlled amplitude;
• a second electrical switch connected to the inverter and the first electrical switch, and configured to open during the AC self-heating mode;
• and
• a battery controller in communication with the plurality of solid-state power switches, the first electrical switch, and the second electrical switch;
• wherein a current output node of the second electrical switch is connected to a current input node of the first electrical switch, such that the second electrical switch is arranged in series with the first electrical switch;
• wherein the second electrical switch is located in-between the first electrical switch and the secondary winding of the transformer;
• wherein the battery controller is configured, in response to calibrated entry criteria, to close the first electrical switch, open the second electrical switch, and control ON/OFF conducting states of the plurality of solid-state power switches to thereby self-heat the battery pack to a predetermined temperature using the AC waveform;
• wherein the calibrated entry criteria include a required charging of the battery pack while a battery temperature of the battery pack is less than a calibrated temperature limit;
• wherein the AC waveform is generated in part through the secondary winding and the capacitor;
• and
• wherein the battery controller is configured, prior to charging the battery pack, to selectively close the first electrical switch, and open the second electrical switch.

A method for performing alternating current (AC) self-heating mode of a battery pack in a battery electric system having a direct current (DC) voltage bus, the method comprising:

• in response to calibrated entry criteria, opening a first electrical switch, closing a second electrical switch connected in parallel with the first electrical switch, and controlling ON/OFF conducting states of a plurality of solid-state power switches of an inverter via a battery controller, wherein the first electrical switch is connected between the inverter and the battery pack, and wherein the second electrical switch is connected to the inverter and the first electrical switch;
• and
• generating an AC waveform through the battery pack at a controlled amplitude through the second electrical switch and a set of the plurality of solid-state power switches having an OFF conducting state to thereby self-heat the battery pack to a predetermined temperature;
• wherein the calibrated entry criteria include a required charging of the battery pack while a battery temperature of the battery pack is less than a calibrated temperature limit;
• wherein the DC voltage bus has a positive voltage rail and a negative voltage rail;
• wherein six of the plurality of solid-state power switches are upper solid-state power switches connected to the positive voltage rail;
• wherein six of the plurality of solid-state power switches are lower solid-state power switches connected to the negative voltage rail;
• wherein the set of the plurality of solid-state power switches having an OFF conducting state includes only one of the upper solid-state power switches and only one of the lower solid-state power switches;
• and
• wherein the battery electric system further comprises:
• a transformer having a primary winding and a secondary winding;
• a capacitor connected in parallel with the battery pack;
• and
• a battery controller is in communication with the plurality of solid-state power switches, the first electrical switch, and the second electrical switch, wherein the battery controller is configured, prior to charging the battery pack, to selectively open the first electrical switch, close the second electrical switch, and control individual ON/OFF conducting states of the plurality of solid-state power switches, and thereby heat the battery pack via the AC waveform, when the battery temperature is less than a calibrated temperature limit.