Broadcast of discharge current based on state-of-health imbalance between battery packs
Systems and methods are described for managing charging and discharging of battery packs. In one or more aspects, a system and method are provided to minimize overcharging of battery cells of specific battery chemistries while still enabling fast charging cycles. In other aspects, a buck converter may be used to reduce a voltage of power used to charge the cells. In further aspects, a fast overcurrent protection circuit is described to address situations involving internal short circuits of a battery cell or battery pack. In yet further aspects, a bypass circuit is provided in series-connected battery packs to improve the charging of undercharged battery packs while also increasing the efficiency of the overall charging process. In other aspects, a circuit is provided that permits a controller to determine a configuration of battery packs. In yet further aspects, a system may determine a discharge current for a collection of battery packs based on each battery pack's state of health (SOH) and forward that determination to an external device.
1. A method comprising:
receiving, by a controller of a master battery pack of a battery system, status information from each battery pack of a plurality of battery packs of the battery system, wherein the status information comprises a first state of health (SoH) value corresponding to a condition of a first battery pack and a second SoH value corresponding to a condition of a second battery pack, wherein the status information from at least one of the battery packs is received via a communication channel;
determining, based on the first SoH value, a first virtual current, corresponding to energy discharged from first battery pack;
determining, based on the second SoH value, a second virtual current, corresponding to energy discharged from the second battery pack;
calculating, by a controller of the master battery pack, a system virtual output current corresponding to energy discharged from the battery system to an end device, wherein the calculation corresponds to a sum of the first virtual current provided from the first battery pack and the second virtual current provided from the second battery pack;
sending, by the master battery pack via the communication channel, a message comprising at least the system virtual output current value; and
causing display, at the end device and based on the message received via the communication channel, of an indication of whether one or more of the system virtual output current, the first virtual current, or the second virtual current exceeds a threshold.
2. The method of claim 1 , wherein the indication of whether the one of the first virtual current or the second virtual current exceeds a threshold comprises a prediction that one of the first battery pack or the second battery pack will fail first.
3. The method of claim 1 , wherein the indication of whether the one of the first virtual current or the second virtual current exceeds a threshold comprises an indication that a corresponding battery pack meets or exceeds a maximum current threshold.
4. The method of claim 1 ,
wherein the first SoH value of the first battery pack corresponds to a relative health of battery cells in the first battery pack, and
wherein the relative health is based on:
internal resistance,
internal impedance;
battery storage capacity,
battery output voltage,
a number of charge-discharge cycles,
a temperature of a battery cell during previous uses,
total energy charged or discharged,
age of a battery cell, or
a combination thereof.
5. The method of claim 1 , further comprising:
determining, by the controller of the master battery pack and based on the first SoH value, a first impedance of the first battery pack based on the first SoH value;
determining, by the controller of the master battery pack and based on the second SoH value, a second impedance of the second battery pack; and
calculating, by the controller of the master battery pack, the first virtual current value based on the first impedance of the first battery pack; and
calculating, by the controller of the master battery pack, the second virtual current value based on the second impedance of the second battery pack.
6. The method of claim 1 , wherein determining the first virtual current able to be provided by the first battery pack and the second virtual current able to be provided by the second battery pack comprises:
determining, by the controller of the master battery pack, a first impedance of the first battery pack based on the first SoH value and a second impedance of the second battery pack based on the second SoH value.
7. The method of claim 5 , comprising determining, by the master battery pack, an impedance of each battery pack of the plurality of battery packs from a lookup table.
8. The method of claim 5 , further comprising calculating, by the master battery pack, an impedance of each battery pack of the plurality of battery packs using an equation.
9. The method of claim 1 , wherein the first battery pack comprises the master battery pack.
10. The method of claim 1 , wherein each battery pack of the plurality of battery packs comprises a controller and a battery management system (BMS) and wherein the method comprises:
determining, periodically by the BMS of the first battery pack, the first SoH value; and
determining, periodically by the BMS of the second battery pack, the second SoH value.
11. The method of claim 1 , further comprising:
causing display, at the second battery pack and based on the message received via the communication channel, of an indication that the second virtual current exceeds a current threshold.
12. The method of claim 1 , further comprising:
augmenting, based on a comparison of the first virtual current and the second virtual current, the message to include one of a first virtual current value or a second virtual current value.
13. The method of claim 1 , further comprising:
triggering, by the master pack and based on a comparison of one of the calculated first virtual current or the calculated second virtual current to the threshold, a preventative action comprising initiating a limp-home mode of operation for the battery system.
14. The method of claim 1 , further comprising:
triggering, by the master pack and based on a comparison of one of the calculated first maximum current or the calculated second maximum current to a threshold, a preventative action comprising disabling a corresponding battery pack.
15. The method of claim 11 , further comprising:
enabling a spare battery pack.
16. A battery system comprising:
a plurality of battery packs, each battery pack of the plurality of battery packs comprising:
a controller;
a communication interface;
a battery management system (BMS); and
memory storing instructions that, when executed by the controller, cause a battery pack of the plurality of battery packs to:
receive, by a controller of a master battery pack of a battery system, status information from each battery pack of a plurality of battery packs of the battery system, wherein the status information comprises a first state of health (SoH) value corresponding to a condition of a first battery pack and a second SoH value corresponding to a condition of a second battery pack, wherein the status information from at least one of the battery packs is received via a communication channel;
determine, based on the first SoH value, a first virtual current, corresponding to energy discharged from first battery pack;
determine, based on the second SoH value, a second virtual current, corresponding to energy discharged from the second battery pack;
calculate, by a controller of the master battery pack, a system virtual output current corresponding to energy discharged from the battery system to an end device, wherein the calculation corresponds to a sum of the first virtual current provided from the first battery pack and the second virtual current provided from the second battery pack;
send, by the master battery pack via the communication channel, a message comprising at least the system virtual output current value; and
cause display, at the end device and based on the message received via the communication channel, of an indication of whether one or more of the system virtual output current, the first virtual current, or the second virtual current exceeds a threshold.
17. The system of claim 15 , wherein the indication of whether the one of the first virtual current or the second virtual current exceeds a threshold comprises a prediction that one of the first battery pack or the second battery pack will fail first.
18. The system of claim 15 , wherein the indication of whether the one of the first virtual current or the second virtual current exceeds a threshold comprises an indication that a corresponding battery pack meets or exceeds a maximum current threshold.
19. The system of claim 16 ,
wherein the first SoH value of the first battery pack corresponds to a relative health of battery cells in the first battery pack, and
wherein the relative health is based on:
internal resistance,
internal impedance;
battery storage capacity,
battery output voltage,
a number of charge-discharge cycles,
a temperature of a battery cell during previous uses,
total energy charged or discharged,
age of a battery cell, or
a combination thereof.
20. Computer readable media storing instructions that, when executed by a processor, cause a battery pack of a battery system to:
receive, by a controller of a master battery pack of a battery system, status information from each battery pack of a plurality of battery packs of the battery system, wherein the status information comprises a first state of health (SoH) value corresponding to a condition of a first battery pack and a second SoH value corresponding to a condition of a second battery pack, wherein the status information from at least one of the battery packs is received via a communication channel;
determine, based on the first SoH value, a first virtual current, corresponding to energy discharged from first battery pack;
determine, based on the second SoH value, a second virtual current, corresponding to energy discharged from the second battery pack;
calculate, by a controller of the master battery pack, a system virtual output current corresponding to energy discharged from the battery system to an end device, wherein the calculation corresponds to a sum of the first virtual current provided from the first battery pack and the second virtual current provided from the second battery pack;
send, by the master battery pack via the communication channel, a message comprising at least the system virtual output current value; and
cause display, at the end device and based on the message received via the communication channel, of an indication of whether one or more of the system virtual output current, the first virtual current, or the second virtual current exceeds a threshold.