Automatic state of charge management system for lithium-ion batteries

1 . A system for maintaining a state of charge of spare batteries, comprising:

a plurality of batteries, wherein each of the plurality of batteries has a given state of charge;

a charger configured to charge each of the plurality of batteries;

a load configured to discharge each of the plurality of batteries, wherein the charger and the load are configured to charge or discharge each of the plurality of batteries to a storage or transportation state of charge;

a controller configured to maintain each of the plurality of batteries at the storage or transportation state of charge by causing the charger or load to respectively charge or discharge one or more batteries from the plurality of batteries to a target state of charge for replacement of one or more batteries of an external system, wherein the target state of charge corresponds to a state of charge of remaining batteries of the external system;

a multiplexor configured to electrically couple each of the plurality of batteries to the controller, wherein one battery of the plurality of batteries is coupled at a given time; and

a human-machine interface coupled to the controller, wherein the human-machine interface is configured to receive one or more inputs to the system and to display a current state of charge for each of the plurality of batteries, wherein the one or more inputs comprise the states of the charge of the one or more batteries of the external system.

2 . The system of claim 1 , wherein the controller is configured to, in response to being unable to communicate with a battery from among the plurality of batteries:

charge the battery to a 100% state of charge;

determine an amount of time for a constant-current load to discharge the battery from the 100% state of charge to the target state of charge;

discharge the battery to the target state of charge by applying the constant-current load for the determined amount of time.

3 . The system of claim 1 , wherein the controller is configured to connect and/or disconnect the plurality of batteries from the system to allow batteries to be added and/or removed from the system.

4 . The system of claim 1 , further comprising a battery management module configured to communicate parameters for each of the plurality of batteries to the controller.

5 . The system of claim 4 , wherein the parameters for each of the plurality of batteries comprises, for each of the plurality of batteries:

the current state of charge,

a state of health,

a voltage,

cell voltages for each cell of the respective battery, and

a temperature.

6 . The system of claim 1 , further comprising a load connection control module configured to physically and electrically couple and uncouple the charger and the load to each of the plurality of batteries.

7 . The system of claim 1 , wherein the plurality of batteries comprises one or more lithium-ion battery modules each having a nominal voltage of 48 volts.

8 . A spares cabinet for maintaining a state of charge of spare batteries, wherein the spares cabinet comprises:

an enclosure configured to enclose one or more components;

a plurality of batteries stored within the enclosure, wherein each of the plurality of batteries has a given state of charge;

a charger configured to charge each of the plurality of batteries;

a load configured to discharge each of the plurality of batteries, wherein the charger and the load are configured to charge or discharge each of the plurality of batteries to a storage or transportation state of charge;

a controller configured to maintain each of the plurality of batteries at the storage or transportation state of charge by causing the charger or load to respectively charge or discharge one or more batteries from the plurality of batteries to a target state of charge for replacement of one or more batteries of an external system, wherein the target state of charge corresponds to a state of charge of remaining batteries of the external system;

a multiplexor configured to electrically couple each of the plurality of batteries to the controller, wherein one battery of the plurality of batteries is coupled at a given time; and

a human-machine interface coupled to the controller, wherein the human-machine interface is configured to receive one or more inputs for the controller and to display a current state of charge for each of the plurality of batteries, wherein the one or more inputs comprise the states of the charge of the one or more batteries of the external system.

9 . The spares cabinet of claim 8 , wherein the controller is configured to, in response to being unable to communicate with a battery from among the plurality of batteries:

charge the battery to a 100% state of charge;

determine an amount of time for a constant-current load to discharge the battery from the 100% state of charge to the target state of charge;

discharge the battery to the target state of charge by applying the constant-current load for the determined amount of time.

10 . The spares cabinet of claim 8 , wherein the controller is configured to connect and/or disconnect the plurality of batteries from the spares cabinet to allow batteries to be added and/or removed from the spares cabinet.

11 . The spares cabinet of claim 8 , further comprising a battery management module configured to communicate parameters for each of the plurality of batteries to the controller.

12 . The spares cabinet of claim 11 , wherein the parameters for each of the plurality of batteries comprises, for each of the plurality of batteries:

the current state of charge,

a state of health,

a voltage,

cell voltages for each cell of the respective battery,

a temperature.

13 . The spares cabinet of claim 8 , further comprising a load connection control module configured to physically and electrically couple and uncouple the charger and the load to each of the plurality of batteries.

14 . The spares cabinet of claim 8 , wherein the plurality of batteries comprises one or more lithium-ion battery modules each having a nominal voltage of 48 volts.

15 . A method for maintaining a state of charge of spare batteries, comprising:

providing a system, comprising:

a charger configured to charge a plurality of batteries,

a load configured to discharge the plurality of batteries,

a controller configured to maintain each of the plurality of batteries at a storage or transportation state of charge by causing the charger or load to respectively charge or discharge one or more batteries from the plurality of batteries to a target state of charge for replacement of one or more batteries of an external system, wherein the target state of charge corresponds to a state of charge of remaining batteries of the external system, and

a multiplexor configured to electrically couple each of the plurality of batteries to the controller, wherein one battery of the plurality of batteries is coupled at a given time;

disconnecting each of the plurality of batteries from the system, wherein each battery of the plurality of batteries has a given state of charge;

reading one or more parameters of a battery from the plurality of batteries; and

determining, based on the parameters, whether or not to charge or discharge the battery to a target state of charge.

16 . The method of claim 15 , wherein the parameters of the battery from the plurality of batteries comprise one or more of: a current state of charge, a state of health, a voltage, a temperature, and one or more cell voltages of the battery.

17 . The method of claim 16 , wherein charging the plurality of batteries comprises:

determining a voltage limit and a current limit for the charger;

sequentially connecting each of the plurality of batteries to the charger to charge each battery;

monitoring, as each respective battery charges, one or more of the parameters of the respective battery; and

in response to each of the plurality of batteries being charged to the target state of charge, disconnecting the plurality of batteries from the charger.

18 . The method of claim 16 , wherein discharging comprises:

sequentially connecting each of the plurality of batteries to the load to discharge each battery, wherein the load is configured to discharge the batteries by a constant current;

monitoring, as each respective battery discharges, one or more of the parameters of the respective battery; and

in response to each of the plurality of batteries being discharged to the target state of charge, disconnecting the plurality of batteries from the load.

19 . The method of claim 15 , wherein further comprising providing a fault or alarm state in response to one or more of: a component failure, a communication loss, or determining one or more issues with a battery from the plurality of batteries.

20 . The method of claim 15 , further comprising entering a maintenance state, wherein in response to entering the maintenance state, the system causes the plurality of batteries to be disconnected from the system to allow a user to add or remove batteries from the system.