Inter-module battery balancing using voltages to select battery sub-modules to power loads
One or more battery sub-modules are selected by obtaining at least one voltage from each battery sub-module and selecting based at least in part on the obtained voltages. The battery sub-modules are electrically connected in series in order to provide power to a primary load. Each battery sub-module includes a plurality of cells electrically connected in series and each battery sub-module further includes a battery management system that monitors the cells in that battery sub-module. Those battery management systems in the selected sub-modules are turned off so that the battery management systems in the selected sub-modules do not consume power at least temporarily from the cells in the selected sub-modules while (1) the battery sub-modules are not providing power to the primary load and (2) the battery sub-modules are not being charged.
1. A system, comprising:
a plurality of battery sub-modules, wherein:
the plurality of battery sub-modules are electrically connected in series in order to provide power to a primary load;
each battery sub-module includes a plurality of cells electrically connected in series; and
each battery sub-module further includes a battery management system that monitors the plurality of cells in that battery sub-module; and
to a controller that is configured to:
select one or more battery sub-modules from the plurality of battery sub-modules, including by:
obtaining at least one voltage from each battery sub-module; and
selecting one or more battery sub-modules based at least in part on the obtained voltages; and
turn off those battery management systems in the one or more selected battery sub-modules so that the battery management systems in the one or more selected battery sub-modules do not consume power at least temporarily from the plurality of cells in the one or more selected battery sub-modules while (1) the plurality of battery sub-modules is not providing power to the primary load and (2) the plurality of battery sub-modules is not being charged.
2. The system recited in claim 1 , wherein selecting the one or more battery sub-modules is based at least in part on a plurality of minimum cell voltages which includes a minimum cell voltage from each battery sub-module in the plurality of battery sub-modules.
3. The system recited in claim 1 , wherein selecting the one or more battery sub-modules is based at least in part on a plurality of maximum cell voltages which includes a maximum cell voltage from each battery sub-module in the plurality of battery sub-modules.
4. The system recited in claim 1 , wherein selecting the one or more battery sub-modules includes:
comparing, for each battery sub-module in the plurality of battery sub-modules, a minimum cell voltage against a voltage threshold in order to identify any battery sub-modules with a minimum cell voltage that does not exceed the voltage threshold; and
selecting one or more of those battery sub-modules with a minimum cell voltage that does not exceed the voltage threshold.
5. The system recited in claim 1 , wherein the controller is further configured to:
determine an imbalance metric associated with a degree of imbalance between battery sub-modules in the plurality of battery sub-modules;
determine whether the imbalance metric exceeds an imbalance threshold; and
in response to determining that the imbalance metric exceeds the imbalance threshold:
performing pre-charging balancing, including by:
selecting one or more battery sub-modules from the plurality of battery sub-modules, including by:
obtaining at least one voltage from each battery sub-module; and
selecting one or more battery sub-modules based at least in part on the obtained voltages; and
turning off those battery management systems in the one or more selected battery sub-modules so that the battery management systems in the one or more selected battery sub-modules do not consume power at least temporarily from the plurality of cells in the one or more selected battery sub-modules while (1) the plurality of battery sub-modules is not providing power to the primary load and (2) the plurality of battery sub-modules is not being charged; and
after performing pre-charging balancing, charging the plurality of battery sub-modules.
6. A method, comprising:
selecting one or more battery sub-modules from a plurality of battery sub-modules, including by:
obtaining at least one voltage from each battery sub-module; and
selecting one or more battery sub-modules based at least in part on the obtained voltages, wherein:
the plurality of battery sub-modules are electrically connected in series in order to provide power to a primary load;
each battery sub-module includes a plurality of cells electrically connected in series; and
each battery sub-module further includes a battery management system that monitors the plurality of cells in that battery sub-module; and
turning off those battery management systems in the one or more selected battery sub-modules so that the battery management systems in the one or more selected battery sub-modules do not consume power at least temporarily from the plurality of cells in the one or more selected battery sub-modules while (1) the plurality of battery sub-modules is not providing power to the primary load and (2) the plurality of battery sub-modules is not being charged.
7. The method recited in claim 6 , wherein selecting the one or more battery sub-modules is based at least in part on a plurality of minimum cell voltages which includes a minimum cell voltage from each battery sub-module in the plurality of battery sub-modules.
8. The method recited in claim 6 , wherein selecting the one or more battery sub-modules is based at least in part on a plurality of maximum cell voltages which includes a maximum cell voltage from each battery sub-module in the plurality of battery sub-modules.
9. The method recited in claim 6 , wherein selecting the one or more battery sub-modules includes:
comparing, for each battery sub-module in the plurality of battery sub-modules, a minimum cell voltage against a voltage threshold in order to identify any battery sub-modules with a minimum cell voltage that does not exceed the voltage threshold; and
selecting one or more of those battery sub-modules with a minimum cell voltage that does not exceed the voltage threshold.
10. The method recited in claim 6 , further comprising:
determining an imbalance metric associated with a degree of imbalance between battery sub-modules in the plurality of battery sub-modules;
determining whether the imbalance metric exceeds an imbalance threshold; and
in response to determining that the imbalance metric exceeds the imbalance threshold:
performing pre-charging balancing, including by:
selecting one or more battery sub-modules from the plurality of battery sub-modules, including by:
obtaining at least one voltage from each battery sub-module; and
selecting one or more battery sub-modules based at least in part on the obtained voltages; and
turning off those battery management systems in the one or more selected battery sub-modules so that the battery management systems in the one or more selected battery sub-modules do not consume power at least temporarily from the plurality of cells in the one or more selected battery sub-modules while (1) the plurality of battery sub-modules is not providing power to the primary load and (2) the plurality of battery sub-modules is not being charged; and
after performing pre-charging balancing, charging the plurality of battery sub-modules.
11. A computer program product, the computer program product being embodied in a non-transitory computer readable storage medium and comprising computer instructions for:
selecting one or more battery sub-modules from a plurality of battery sub-modules, including by:
obtaining at least one voltage from each battery sub-module; and
selecting one or more battery sub-modules based at least in part on the obtained voltages, wherein:
the plurality of battery sub-modules are electrically connected in series in order to provide power to a primary load;
each battery sub-module includes a plurality of cells electrically connected in series; and
each battery sub-module further includes a battery management system that monitors the plurality of cells in that battery sub-module; and
turning off those battery management systems in the one or more selected battery sub-modules so that the battery management systems in the one or more selected battery sub-modules do not consume power at least temporarily from the plurality of cells in the one or more selected battery sub-modules while (1) the plurality of battery sub-modules is not providing power to the primary load and (2) the plurality of battery sub-modules is not being charged.
12. The computer program product recited in claim 11 , wherein selecting the one or more battery sub-modules is based at least in part on a plurality of minimum cell voltages which includes a minimum cell voltage from each battery sub-module in the plurality of battery sub-modules.
13. The computer program product recited in claim 11 , wherein selecting the one or more battery sub-modules is based at least in part on a plurality of maximum cell voltages which includes a maximum cell voltage from each battery sub-module in the plurality of battery sub-modules.
14. The computer program product recited in claim 11 , wherein selecting the one or more battery sub-modules includes:
comparing, for each battery sub-module in the plurality of battery sub-modules, a minimum cell voltage against a voltage threshold in order to identify any battery sub-modules with a minimum cell voltage that does not exceed the voltage threshold; and
selecting one or more of those battery sub-modules with a minimum cell voltage that does not exceed the voltage threshold.
15. The computer program product recited in claim 11 , further comprising computer instructions for:
determining an imbalance metric associated with a degree of imbalance between battery sub-modules in the plurality of battery sub-modules;
determining whether the imbalance metric exceeds an imbalance threshold; and
in response to determining that the imbalance metric exceeds the imbalance threshold:
performing pre-charging balancing, including by:
selecting one or more battery sub-modules from the plurality of battery sub-modules, including by:
obtaining at least one voltage from each battery sub-module; and
selecting one or more battery sub-modules based at least in part on the obtained voltages; and
turning off those battery management systems in the one or more selected battery sub-modules so that the battery management systems in the one or more selected battery sub-modules do not consume power at least temporarily from the plurality of cells in the one or more selected battery sub-modules while (1) the plurality of battery sub-modules is not providing power to the primary load and (2) the plurality of battery sub-modules is not being charged; and
after performing pre-charging balancing, charging the plurality of battery sub-modules.