Battery pack balancing controls for multiple battery pack systems

1 . An electric vehicle charging system comprising:

a switchable battery including at least two battery packs and a controllable switch that is arranged to selectively isolate the at least two battery packs from one another and connect each of the at least two battery packs to separate charging sources in a fast-charging configuration, and to connect the at least two battery packs in parallel in a drive configuration;

a plurality of sensors configured to measure one or more characteristics of the at least two battery packs; and

a controller configured to:

control the configuration of the switchable battery and operate the controllable switch to select between the fast-charging configuration and the drive configuration;

calculate an adjustment to a charging current of a follower one of the at least two battery packs based on the one or more characteristics; and

transmit the adjustment to a charging source associated with the follower one of the at least two battery packs,

wherein the controller calculates the adjustment to the charging current to balance at least one of the one or more characteristics of the at least two battery packs, the adjustment comprising a dynamic scaling factor that scales a baseline charge current of the follower pack, wherein a value of the scaling factor less than one reduces the applied charging current and thereby reduces a charging speed of the follower pack;

wherein the controller is further configured to identify a first battery pack of the at least two battery packs as a master pack, wherein the first battery pack has a lowest voltage level of the at least two battery packs;

wherein the one of the at least two battery packs for which the adjustment to the charging current is calculated does not include the master pack, and wherein the adjustment for a follower pack is a reduction to a baseline charging current according to a proportional-integral function of a difference between a voltage of the master pack and a voltage of the follower pack.

2 . The electric vehicle charging system of claim 1 , wherein the one or more characteristics includes one or more of a terminal voltage, an open circuit voltage, a state-of-charge, a temperature and an input current level, wherein the open circuit voltage of each battery pack is computed by comparing a resistive delta from a measured terminal voltage using battery current and an estimated pack resistance.

3 . The electric vehicle charging system of claim 1 , wherein the identification of the master pack is performed periodically during charging of the switchable battery.

4 . The electric vehicle charging system of claim 1 wherein the controller is configured to only identify the master pack and only calculate the adjustment to the charging current based on a determination that a state-of-charge of at least one of the at least two battery packs is above a threshold minimum.

5 . The electric vehicle charging system of claim 1 , wherein the controller is further configured to monitor the one or more characteristics of the at least two battery packs and to identify an anomaly with one of the at least two battery packs or the charging source for one of the at least two battery packs, to determine whether the anomaly is associated with a charging source or with a battery pack, to remove a battery pack associated with a charging-source anomaly from a battery-pack balancing algorithm, and to reconfigure routing between a charging port and the associated battery pack after other battery packs have completed charging to complete charging for the associated battery pack by a different port.

6 . The electric vehicle charging system of claim 5 , wherein the controller is further configured to disable a battery pack of the at least two battery packs based on a determination that the anomaly is a charging fault with the battery pack and to reconfigure a drive mode to not use the disabled battery pack.

7 . A method for charging an electric vehicle, the method comprising:

configuring a switchable battery of the electric vehicle in a fast-charging configuration by operating a controllable switch to isolate a first battery pack from a second battery pack, and connecting the first battery pack to a first charging source and the second battery pack to a second charging source;

obtaining one or more characteristics of the first battery pack and the second battery pack;

calculating a first baseline charging current level for the first battery pack based on the one or more characteristics of the first battery pack;

calculating a second baseline charging current level for the second battery pack based on the one or more characteristics of the second battery pack;

identifying the first battery pack as a master pack and the second battery pack as a follower pack based on a determination that the first battery pack has a lower voltage level than the second battery pack;

calculating an adjustment for the follower pack, the adjustment comprising a dynamic scaling factor that scales the second baseline charging current level, wherein a value of the scaling factor less than one reduces the applied charging current and thereby reduces a charging speed of the follower pack, the scaling factor being determined according to a proportional-integral function of a difference between a voltage of the master pack and a voltage of the follower pack;

transmitting the first baseline charging current level to the first charging source; and

transmitting the second baseline charging current level and the adjustment to the second charging source.

8 . The method of claim 7 , wherein the one or more characteristics includes one or more of a terminal voltage, an open circuit voltage, a state-of-charge, a temperature and an input current level, wherein the open-circuit voltage of each battery pack is computed by comparing a resistive delta from a measured terminal voltage using battery current and an estimated pack resistance.

9 . The method of claim 7 , wherein the identification of the master pack is performed periodically during charging of the switchable battery.

10 . The method of claim 7 , wherein the adjustment is a reduction to the second baseline charging current level.

11 . The method of claim 7 , wherein the adjustment to the second baseline charging current level is configured to balance at least one of the one or more characteristics to the first battery pack and the second battery pack.

12 . The method of claim 7 , wherein the identifying the first battery pack as the master pack and calculating the adjustment to the second baseline charging current level are only performed based on a determination that a state-of-charge of at least one of the first battery pack and the second battery pack is above a threshold minimum.

13 . An electric vehicle, comprising:

a first charging source;

a second charging source;

a switchable battery including a first battery pack and a second battery pack that are selectively arranged in one of a fast-charging configuration and a drive configuration, wherein the fast-charging configuration includes connecting the first battery pack to the first charging source and the second battery pack to the second charging source and the drive configuration includes connecting each of the first battery pack and the second battery pack in parallel; and a controllable switch arranged to selectively isolate the first battery pack and the second battery pack from one another in the fast-charging configuration and to connect the first battery pack and the second battery pack in parallel in the drive configuration;

a plurality of sensors configured to measure one or more characteristics of the first battery pack and the second battery pack, the one or more characteristics including an open-circuit voltage of each battery pack, wherein the open-circuit voltage is computed by comparing a resistive delta from a measured terminal voltage using battery current and an estimated pack resistance; and

a controller configured to:

control the configuration of the switchable battery and operate the controllable switch to select between the fast-charging configuration and the drive configuration;

identify, during fast-charging, a master one of the first battery pack and the second battery pack as having a lowest voltage level and designate a remaining battery pack as a follower pack, and perform the identification periodically during charging;

calculate an adjustment to a charging current of one of follower pack based on the one or more characteristics; and

transmit the adjustment to a charging source associated with follower pack, wherein the controller calculates the adjustment to the charging current to balance at least one of the one or more characteristics of the first battery pack and the second battery pack, the adjustment comprising a dynamic scaling factor that scales a baseline charge current of the follower pack, wherein a value of the scaling factor less than one reduces the applied charging current and thereby reduces a charging speed of the follower pack, the scaling factor being determined according to a proportional-integral function of a difference between a voltage of the master pack and a voltage of the follower pack, and wherein the controller is configured to only identify the master pack and only calculate the adjustment to the charging current based on a determination that a state-of-charge of at least one of the first battery pack and the second battery pack is above a threshold minimum; and

monitor the one or more characteristics during fast-charging to identify an anomaly with one of the first battery pack and the second battery pack or with one of the first charging source and the second charging source, to determine whether the anomaly is associated with a charging source or with a battery pack, to remove a battery pack associated with a charging-source anomaly from a battery-pack balancing algorithm, to reconfigure routing between a charging port and the associated battery pack after other battery packs have completed charging to complete charging for the associated battery pack by a different port, and to disable a battery pack when the anomaly is a charging fault with the battery pack and to reconfigure a drive mode to not use the disabled battery pack.

14 . The electric vehicle of claim 13 , wherein the adjustment to the charging current is computed according to ΔI=kp(V2−V1)+kI ∫(V2−V1), where V1 is a voltage of the master pack and V2 is a voltage of the follower pack, and kp and kI are constants.

15 . The electric vehicle of claim 13 , wherein the state-of-charge threshold minimum is approximately seventy percent.

16 . The electric vehicle of claim 13 , wherein baseline charging current levels for the first battery pack and the second battery pack are determined by a battery management system based on battery voltage, temperature, and state of charge.

17 . The electric vehicle of claim 13 , wherein determining whether an anomaly is associated with a charging source includes determining that a requested charging current for an identified one of the first battery pack and the second battery pack is not within a threshold of a charging current being applied to the identified battery pack.

18 . The electric vehicle charging system of claim 1 , wherein the controller is configured to identify the master pack and calculate the adjustment to the charging current only when a state-of-charge of at least one of the at least two battery packs is above approximately seventy percent.