Power management of high-current fast-charging battery

1. A method for managing powerflow of a multi-pack rechargeable energy storage system (RESS) having a parallel-connected first battery pack and second battery pack with different characteristics, wherein the first battery pack and the second battery pack have respective maximum current limits, the method comprising:

predicting a corresponding first terminal voltage and second terminal voltage for the first battery pack and the second battery pack, respectively, via a controller using the respective maximum current limits;

receiving, via the controller, a requested operating mode of the multi-pack RESS, wherein the requested operating mode is either a charging mode or a discharging mode of the multi-pack RESS;

selecting the first terminal voltage or the second terminal voltage as a selected voltage based on the requested operating mode, including selecting a maximum of the first terminal voltage or the second terminal voltage when the requested operating mode is the discharging mode, and selecting a minimum of the first terminal voltage or the second terminal voltage when the requested operating mode is the charging mode;

predicting a first pack current and a second pack current flowing through the first battery pack and the second battery pack, respectively, using the selected voltage and corresponding battery state space models;

predicting a total power capability of the multi-pack RESS over a predetermined prediction horizon using the first pack current and the second pack current to thereby generate a plurality of predicted power capability values; and

controlling the requested operating mode over the predetermined prediction horizon, via the controller, using the plurality of predicted power capability values.

2. The method of claim 1 , the method further comprising:

receiving a fast-charging voltage and current from an offboard fast-charging station, via the multi-pack RESS, during a fast-charging operation;

wherein the requested operating mode is the charging mode, and controlling the requested operating mode occurs during the charging mode by controlling the fast-charging operation via the controller.

3. The method of claim 1 , wherein the requested operating mode is the discharging mode, and wherein controlling the requested operating mode includes energizing a rotary electric machine via the multi-pack RESS and a power inverter module.

4. The method of claim 1 , wherein the predetermined prediction horizon includes at least five future time points.

5. The method of claim 1 , wherein the controller includes hierarchically-arranged first and second controllers, predicting the second terminal voltage is accomplished via the second controller using a second one of the battery state space models and communicated to the first controller, predicting the first terminal voltage is accomplished via the first controller using a first of the battery state space models, and predicting the total power capability and controlling the requested operating mode is accomplished via the first controller.

6. The method of claim 5 , wherein the first and second controllers are first and second vehicle integration control modules (VICMs) of a motor vehicle.

7. The method of claim 1 , wherein the multi-pack RESS includes a third battery pack connected to the first and second battery packs via a DC-DC converter, such that the third battery pack has a pack voltage that is less than a pack voltage of the first and second battery packs.

8. The method of claim 7 , wherein the third battery pack has a pack voltage of 48V and the first and second battery packs have a pack voltage of at least 370V.

9. A powertrain system comprising:

a multi-pack rechargeable energy storage system (RESS) having:

a parallel-connected first battery pack and second battery pack; and

a first pack sensor and a second pack sensor connected to the respective first and second battery packs, each of the first pack sensor and the second pack sensor being configured to measure a corresponding pack current, voltage, and temperature of the first battery pack and the second battery pack;

a power inverter module (PIM) connected to the multi-pack RESS;

a rotary electric machine connected to the PIM and having an output member coupled to a load; and

a controller in communication with the first pack sensor and the second pack sensor, and operable for managing powerflow of the multi-pack RESS using the measured pack current, voltage, and temperature, wherein the controller is programmed with a corresponding maximum current limit of the first battery pack and the second battery pack, and is configured to:

predict a first terminal voltage and a second terminal voltage for the first battery pack and the second battery pack, respectively, using the corresponding maximum current limit;

receive a requested operating mode of the multi-pack RESS, wherein the requested operating mode is either a charging mode or a discharging mode of the multi-pack RESS;

select the first terminal voltage or the second terminal voltage as a selected voltage based on the requested operating mode, the selected voltage including a maximum of the first terminal voltage or the second terminal voltage when the requested operating mode is the discharging mode and a minimum of the first terminal voltage or the second terminal voltage when the requested operating mode is the charging mode;

predict a pack current flowing through each of the first battery pack and the second battery pack using the selected voltage and corresponding battery state space models;

predict a total power capability of the multi-pack RESS over a predetermined prediction horizon using the pack current of the first battery pack and the second battery pack to thereby generate a plurality of predicted power capability values; and

control the requested operating mode over the predetermined prediction horizon using the plurality of predicted power capability values.

10. The powertrain system of claim 9 , wherein the multi-pack RESS is configured to receive a fast-charging voltage and current from an offboard fast-charging station during a fast-charging operation, the requested operating mode is the charging mode, and the controller is configured to control the fast-charging operation during the charging mode.

11. The powertrain system of claim 9 , wherein the requested operating mode is the discharging mode, and wherein the controller is configured to control the requested operating mode by energizing the rotary electric machine via the multi-pack RESS and the power inverter module.

12. The powertrain system of claim 9 , wherein the predetermined prediction horizon includes at least five future time points.

13. The powertrain system of claim 12 , wherein relative to a current time point (k)=0 seconds (s), the at least five future time points include k=0.1 s, 1 s, 2 s, 10 s, and 20 s.

14. The powertrain system of claim 9 , wherein the controller includes hierarchically-arranged first and second controllers, the second controller is configured to predict the second terminal voltage using a second one of the battery state space models and communicate the second terminal voltage to the first controller, and the first controller is configured to predict the terminal voltage using a first one of the battery state space models, predict the total power capability, and control the requested operating mode.

15. The powertrain system of claim 14 , wherein the first and second controllers are respective first and second vehicle integration control modules (VICMs) of a motor vehicle, and wherein the load is a set of road wheels of the motor vehicle.

16. The powertrain system of claim 9 , wherein each of the battery state space models include a plurality of battery parameters for the first battery pack and the second battery pack, respectively, including a state of charge, and open circuit voltage, and a battery impedance.

17. The powertrain system of claim 9 , wherein the multi-pack RESS includes a third battery pack connected to the first battery pack and the second battery pack via a DC-DC converter, such that the third battery pack has a pack voltage that is less than a pack voltage of the first battery pack and the second battery pack.

18. The powertrain system of claim 17 , wherein the third battery pack has a pack voltage of 48V, and the first battery pack and the second battery pack each have a respective pack voltage of at least 370V.