Battery system bi-stable relay control

A method comprising:

• determining, using one or more processors of a battery control unit, a key state of a vehicle, wherein the key state comprises a key-on state and a key-off state;
• determining, using one or more processors of the battery control unit, a first voltage of a first battery, wherein the first battery is configured to be coupled to an electrical system, and wherein the first battery comprises a first battery chemistry;
• determining, using one or more processors of the battery control unit, a second voltage a second battery, wherein the second battery comprises a second battery chemistry that has a higher coulombic efficiency than the first battery chemistry;
• instructing, using one or more processors of a battery control unit, a bi-stable relay to switch from an open position to a closed position to electrically connect the second battery to the electrical system based at least in part on the first voltage of the first battery, the second voltage of the second battery, and the key state of the vehicle;
• and
• instructing, using one or more processors of the battery control unit, the bi-stable relay to switch from the closed position to the open position to electrically disconnect the second battery from the electrical system based at least in part on the first voltage of the first battery, the second voltage of the second battery, and the key state of the vehicle.

A battery control unit to be deployed in a battery system of a vehicle, comprising:

• a processor configured to be communicatively coupled to a bi-stable relay electrically coupled between a first battery of the battery system and an electrical system of the vehicle, wherein:
• the first battery comprises a first battery chemistry different from a second battery chemistry used in a second battery of the battery system;
• and
• the bi-stable relay is configured to:
• electrically disconnect the first battery from the electrical system while in an open position;
• and
• electrically connect the first battery to the electrical system in parallel with the second battery while in a closed position;
• and
• memory communicatively coupled to the processor, wherein the memory is configured to store instructions, which when executed by the processor, cause the processor to:
• determine a key state of the vehicle, wherein the key state comprises a key-on state and a key-off state;
• determine voltage of the first battery in the battery system and voltage of the second battery in the battery system;
• and
• output one or more control signals based at least in part on the key state of the vehicle, the voltage of the first battery, and the voltage of the second battery that selectively instruct the bi-stable relay to electrically disconnect the first battery from the electrical system of the vehicle.
• control operation of an alternator during regenerative breaking to charge the second battery and to output a second voltage otherwise.