Large-format battery management system with limp home mode
A battery system with a large-format Li-ion battery powers attached equipment by discharging battery cells distributed among a plurality of battery packs. The discharging of the battery cells is controlled in an efficient manner while preserving the expected life of the Li-ion battery cells. Each battery pack internally supports a battery management system and may have identical components, thus supporting an architecture that easily scales to higher power/energy. Battery packs may be added or removed without intervention with a user, where one of battery packs serves as a master battery pack and the remaining battery packs serve as slave battery packs. When the master battery pack is removed, one of the slave battery packs becomes the master battery pack. Charging and discharging of the battery cells is coordinated by the master battery pack with the slave battery packs over a communication channel such as a controller area network (CAN) bus.
1. A first battery pack configured for installation in a battery system for electrically powering an end device, wherein all installed battery packs are communicatively coupled by a communication channel in the battery system and have identical electrical and electronic components, the first battery pack comprising:
one or more battery cells;
a communication interface circuit configured to interface to the communication channel;
a power bus interface circuit configured to interface with a power bus and to provide electrical power to the end device;
a controller comprising at least one processor, wherein the controller of the first battery pack is configured to be either one of the controller of a master battery pack or the controller of a slave battery pack of the battery system; and
a memory storing controller instructions that, when executed by the at least one processor, cause the controller to:
determine that the first battery pack is the master battery pack of the battery system;
when the first battery pack receives a first failure notification message indicative of a first catastrophic failure at a second battery pack over the communication channel via the communication interface circuit, determine that a first spare battery pack is available;
when the first spare battery pack is available and an additional battery pack is needed to power the end device, send a first enable message to the first spare battery pack over the communication channel, wherein the first enable message instructs the first spare battery pack to discharge onto the power bus; and
when the first battery pack receives the first failure notification message indicative of the first catastrophic failure at the second battery pack, send a first disable message to the second battery pack over the communication channel, wherein the first disable message instructs the second battery pack to terminate discharging onto the power bus.
2. The first battery pack of claim 1 , wherein the controller instructions, when executed by the at least one processor, further cause the controller to:
when the first battery pack is the master battery pack of the battery system:
when no spare battery pack is available, send a degradation alert message to the end device.
3. The first battery pack of claim 2 , wherein the controller instructions, when executed by the at least one processor, further cause the controller to:
when the first battery pack is the master battery pack of the battery system:
when the end device does not comply with the degraded alert message, initiate shutdown of the battery system.
4. The first battery pack of claim 3 , wherein the controller instructions, when executed by the at least one processor, further cause the controller to:
when the first battery pack is the master battery pack of the battery system:
instruct all battery packs of the battery system from discharging onto the power bus.
5. The first battery pack of claim 1 , wherein the controller instructions, when executed by the at least one processor, further cause the controller to:
when the first battery pack is the master battery pack of the battery system:
when a plurality of spare battery packs are available, select a highest state of charge (SoC) spare battery pack from the plurality of spare battery packs, wherein the highest SoC spare battery pack is characterized by a highest SoC value of all of the plurality of spare battery packs; and
send a second enable message to the highest SoC spare battery pack, wherein the second enable message instructs the highest SoC spare battery pack to discharge onto the power bus.
6. The first battery pack of claim 1 , wherein the communication channel comprises a controller area network (CAN) bus.
7. The first battery pack of claim 1 , wherein the controller instructions, when executed by the at least one processor, further cause the controller to:
when the first battery pack is the master battery pack of the battery system:
monitor the one or more battery cells;
based on the monitoring, determine whether a second catastrophic failure has occurred;
when the second catastrophic failure has occurred, determine whether the first spare battery pack is available;
when the first spare battery pack is available, send the first enable message to the first spare battery pack, wherein the first enable message instructs the first spare battery pack to discharge onto the power bus; and
disable the first battery pack from discharging onto the power bus.
8. The first battery pack of claim 1 , wherein the first spare battery pack comprises a controller configured to:
determine that the first spare battery pack is the slave battery pack of the battery system;
monitor battery cells in the first spare battery pack;
based on the monitoring, determine whether a third catastrophic failure has occurred; and
when the third catastrophic failure has occurred, send a second failure notification message to the master battery pack of the battery system.
9. The first battery pack of claim 8 , wherein the controller of the first spare battery pack is configured to:
in response to the sending of the second failure notification message, receive a second disable message from the master battery pack; and
in response to the receiving of the second disable message, terminate discharging onto the power bus.
10. The first battery pack of claim 1 , wherein the controller instructions, when executed by the at least one processor, further cause the controller to:
when the first battery pack detects an internal catastrophic failure, terminate discharging the first battery pack onto the power bus;
when at least one spare battery pack is available, enable one of the at least one spare battery pack;
when no spare battery packs is available, send a degradation alert message to the end device; and
maintain the first battery pack as the master battery pack of the battery system.
11. The first battery pack of claim 1 , wherein the controller instructions, when executed by the at least one processor, further cause the controller to:
when the first battery pack detects an internal catastrophic failure, internally terminate discharging the first battery pack onto the power bus; and
remove the first battery pack from being the master battery pack.
12. The first battery pack of claim 1 , wherein the controller instructions, when executed by the at least one processor, further cause the controller to:
when the first battery pack fails to receive any messages from the second battery pack over the communications channel, attempt to disable the second battery pack from discharging onto the power bus; and
adjust a power level over the power bus to the end device.
13. A method of powering an end device by a power bus of a battery system, the method comprising:
after receiving a failure notification message indicative of a catastrophic failure at a slave battery pack over a communication channel, determining, by the master battery pack, that a first spare battery pack is available;
when the first spare battery pack is available and an additional battery pack is needed to power the end device, sending, by the master battery pack, an enable message to the first spare battery pack over the communication channel, wherein the enable message instructs the first spare battery pack to discharge onto the power bus; and
when the master battery pack receives the failure notification message indicative of a catastrophic failure at the slave battery pack, sending, by the master battery pack, a disable message to the slave battery pack, wherein the disable message instructs the slave battery pack to terminate discharging onto the power bus.
14. The method of claim 13 , comprising:
when the end device is not configured for degraded operation, initiating shutdown of the battery system.
15. The method of claim 13 , comprising:
when a plurality of spare battery packs are available, selecting a highest state of charge (SoC) spare battery pack from the plurality of spare battery packs, wherein the highest SoC spare battery pack is characterized by a highest SoC value of all of the plurality of spare battery packs; and
sending the enable message to the highest SoC spare battery pack, wherein the enable message instructs the highest SoC spare battery pack to discharge onto the power bus.
16. The method of claim 13 , comprising:
monitoring, by the slave battery pack, one or more battery cells;
based on the monitoring, determining, by the slave battery pack, whether the catastrophic failure has occurred; and
when the catastrophic failure has occurred, sending, by the slave battery pack, the failure notification message to the master battery pack of the battery system.
17. The method of claim 16 , comprising:
in response to the sending of the failure notification message, receiving, by the slave battery pack, the disable message from the master battery pack; and
in response to the receiving of the disable message, terminating discharging, by the slave battery pack, onto the power bus.
18. A battery system configured for electrically powering an end device and comprising a plurality of battery packs, the battery system comprising:
a slave battery pack; and
a master battery pack including:
a first communication interface circuit configured to interface to a controller area network (CAN) bus;
a first controller comprising at least one processor; and
a first memory storing controller instructions that, when executed by the at least one processor, cause the first controller to:
when the master battery pack receives a failure notification message from the slave battery pack over the CAN bus via the first communication interface circuit and when an extra battery pack is needed, determine whether a first spare battery pack is available, wherein the failure notification message is indicative of a catastrophic failure at the slave battery pack;
when the first spare battery pack is an only spare battery pack and when the extra battery pack is needed, send an enable message to the first spare battery pack, wherein the enable message instructs the first spare battery pack to discharge onto a power bus; and
when the master battery pack receives the failure notification message from the slave battery pack, send a disable message to the slave battery pack, wherein the disable message instructs the slave battery pack to terminate discharging onto the power bus.
19. The battery system of claim 18 , wherein the first memory storing controller instructions that, when executed by the at least one processor, cause the first controller to:
when degraded operation is not acceptable to the end device, initiate shutdown of the battery system.
20. The battery system of claim 19 , wherein the first memory storing controller instructions that, when executed by the at least one processor, cause the first controller to:
instruct all battery packs of the battery system from discharging onto the power bus.
21. The battery system of claim 18 , wherein the first memory storing controller instructions that, when executed by the at least one processor, cause the first controller to:
when a plurality of spare battery packs is available, select a highest SoC spare battery pack from the plurality of spare battery packs, wherein the highest SoC spare battery pack is characterized by a highest state of charge (SoC) value of all of the plurality of spare battery packs; and
send the enable message to the highest SoC spare battery pack, wherein the enable message instructs the highest SoC spare battery pack to discharge onto the power bus.
22. The battery system of claim 18 , wherein the slave battery pack includes:
a second communication interface circuit configured to interface to a controller area network (CAN) bus;
a second controller comprising one or more processors;
one or more battery cells; and
a second memory storing controller instructions that, when executed by the one or more processors, cause the first controller to:
monitor the one or more battery cells;
based on the monitoring, determine whether the catastrophic failure has occurred; and
when the catastrophic failure has occurred, send the failure notification message to the master battery pack of the battery system.
23. The battery system of claim 22 , wherein the second memory storing controller instructions that, when executed by the one or more processors, cause the second controller to
in response to the sending the failure notification message, receive the disable message from the master battery pack; and
in response to the receiving the disable message, terminate discharging onto the power bus.