Hybrid transmission dc-supply (dis)connect

A method for a hybrid transmission, the method comprising:

• controlling current to/from a battery to within a threshold of zero;
• adjusting a voltage setpoint of a first inverter of a first electric motor;
• disconnecting the battery from the first electric motor and a second electric motor by opening a battery contact in response to a DC contactor current less than a threshold current;
• and
• restoring a nominal voltage setpoint for the first inverter of the first electric motor.

A transmission, comprising:

• an engine;
• a first electric motor having a first inverter;
• a second electric motor having a second inverter;
• a battery which may be selectively coupled to at least one of the first electric motor and the second electric motor via a battery contactor;
• and
• a controller storing instructions in non-transitory memory that, when executed, cause the controller to, in response to a request to transition the transmission from a first mode to a second mode:
• control current to/from the battery to within a non-zero threshold of zero;
• adjust a voltage setpoint of the first inverter of the first electric motor that is equal to a sum of a voltage of the battery and a voltage difference between the battery and the transmission,
• apply a DC current threshold to the first electric motor, wherein the first inverter provides no more DC current than requested;
• disconnect the battery to the first electric motor and the second electric motor by opening the battery contactor in response to a DC contactor current less than a threshold;
• and,
• restore a nominal voltage setpoint to the first electric motor;
• wherein in the first mode, the battery, the first electric motor, and the second electric motor are used to power rotation of a transmission output shaft, and wherein in the second mode, the engine, the first electric motor, and the second electric motor are used to power rotation of the transmission output shaft.