System and method for maximizing a battery pack total energy metric

1. A method for maximizing a battery pack total energy metric for a battery pack comprising N battery cells, the method comprising:

receiving a battery cell charge capacity estimate indicative of a charge capacity of a battery cell for all battery cells in the battery pack;

composing battery pack configurations comprising subsets of the total N battery cells;

evaluating a battery pack energy metric for every battery pack configuration that is composed;

selecting the battery pack configuration that has the maximum battery pack energy metric;

abandoning any battery cells that are not included in the battery pack configuration that has the maximum battery pack energy metric; and

storing values representing the selected battery pack configuration in a memory.

2. The method of claim 1 , wherein composing battery pack configurations comprising subsets of the total N battery cells comprises:

sorting battery cell charge capacities in order from 1 to N; and

composing N different battery pack configurations denoted P k for k=1 through N, such that configuration P k comprises battery cells k through N.

3. The method of claim 1 , wherein the battery pack energy metric is defined to be the battery pack total energy of the configuration being evaluated.

4. The method of claim 1 wherein the battery pack energy metric is defined to be a function of the number of cells in the configuration being evaluated multiplied by the battery pack total energy of the configuration being evaluated.

5. The method of claim 1 , wherein the step of composing battery pack configurations comprising subsets of the total N battery cells is performed by selecting a first subset that includes all battery cells in the battery pack, a second subset that includes all batteries cells in the battery pack except the battery cell having the lowest charge capacity, and a third subset that includes all battery cells in the second subset except the battery cell having the next lowest charge capacity.

6. The method of claim 5 , wherein each subsequent subset of the total N battery cells includes all of the battery cells in the prior subset except the battery cell having the next lowest charge capacity.

7. The method of claim 1 , wherein the step of abandoning a battery cell means that an abandoned battery cell is ignored for the purposes of computing which battery cells to equalize, when determining a maximum discharge power or energy, and when controlling the battery pack charging process, except for consideration of safety issues.

8. The method of claim 1 , wherein the step of abandoning a battery cell means that the lower voltage of an abandoned battery cell is not restricted by a minimum design voltage during discharge and a charge capacity of the abandoned battery is allowed to collapse to zero.

9. A system for maximizing a battery pack total energy metric for a battery pack comprising N battery cells, the system comprising:

a computer configured to receive a battery cell charge capacity estimate indicative of a charge capacity of a battery cell for all battery cells in the battery pack;

the computer further configured to compose battery pack configurations comprising subsets of the total N battery cells;

the computer further configured to evaluate a battery pack energy metric for every battery pack configuration that is composed;

the computer further configured to select the battery pack configuration that has the maximum battery pack energy metric;

the computer further configured to abandon battery cells that are not included in the battery pack configuration that has the maximum battery pack energy metric; and

the computer further configured to store values representing the selected battery pack configuration in a memory.

10. The system of claim 9 , wherein the computer is further configured to compose battery pack configurations comprising subsets of the total N battery cells by selecting a first subset that includes all battery cells in the battery pack, a second subset that includes all batteries cells in the battery pack except the battery cell having the lowest charge capacity, and a third subset that includes all battery cells in the second subset except the battery cell having the next lowest charge capacity.

11. The system of claim 10 , wherein each subsequent subset of the total N battery cells includes all of the battery cells in the prior subset except the battery cell having the next lowest charge capacity.

12. The system of claim 9 , wherein an abandoned battery cell means that the abandoned battery cell is ignored for the purposes of computing which battery cells to equalize, when determining a maximum discharge power or energy, and when controlling the battery pack charging process, except for consideration of safety issues.

13. The system of claim 9 , wherein an abandoned battery cell means that a lower voltage of the abandoned battery cell is not restricted by a minimum design voltage during discharge and a charge capacity of the abandoned battery cell is allowed to collapse to zero.