Cell matching across multiple characteristics during battery assembly
For each cell in a plurality of cells from a same manufacturing run, a first and a second cell characteristic are received in order to obtain a plurality of cell characteristics. For each cell, a batch compatibility number that is associated with a number of compatible cells that that cell is compatible with is determined based at least in part on the plurality of cell characteristics. The plurality of cells is sorted according to the batch compatibility numbers to obtain a sorted list of cells. A plurality of compatible cells to include in a battery is selected from the plurality of cells, including by evaluating the plurality of cells according to the order of the sorted list of cells and beginning with the lowest batch compatibility number.
1. A method, comprising:
providing a plurality of cells associated with a plurality of cell characteristics;
for each cell among the plurality of cells, determining a batch compatibility number based at least in part on the plurality of cell characteristics associated with the plurality of cells, wherein the batch compatibility number indicates a number of compatible cells with that cell;
evaluating the plurality of cells according to the batch compatibility numbers;
identifying a plurality of compatible cells based on evaluating; and
assembling a battery by including the plurality of compatible cells from the plurality of cells in the battery.
2. The method of claim 1 , wherein the plurality of cells are evaluated beginning with a cell with a lowest or highest batch compatibility number.
3. The method recited in claim 1 , wherein the plurality of cell characteristics includes one of more of: a capacity, an open circuit voltage, a resistance, or a self-discharge rate.
4. The method recited in claim 1 , wherein determining the batch compatibility number includes generating a cell compatibility matrix which indicates, for the plurality of cells, whether a given pair of cells is compatible.
5. The method recited in claim 1 , wherein determining the batch compatibility number includes:
determining a first difference between a first cell in the plurality of cells and a second cell in the plurality of cells for a first cell characteristic;
determining a second difference between the first cell and the second cell for a second cell characteristic; and
when (1) the first difference does not exceed a first tolerance associated with the first cell characteristic and (2) the second difference does not exceed a second tolerance associated with the second cell characteristic, declaring the first cell and the second cell to be compatible.
6. The method recited in claim 1 , further comprising:
determining, for each tied cell in a plurality of tied cells, a set of compatible cells in order to obtain a plurality of sets of compatible cells; and
breaking a tie between the plurality of tied cells based at least in part on uniqueness associated with the plurality of sets of compatible cells and one or more batch compatibility numbers associated with the plurality of sets of compatible cells.
7. The method recited in claim 6 , wherein breaking the tie between the plurality of tied cells comprises:
sorting the plurality of sets of compatible cells based at least in part on the batch compatibility numbers associated with the plurality of sets of compatible cells to obtain a plurality of sorted lists of compatible cells;
selecting two or more compatible cells to compare from different sorted lists of compatible cells, wherein the selected compatible cells are at a same level in their respective sorted lists of compatible cells; and
when a minimum batch compatibility number, associated with the selected compatible cells to compare, is unique, selecting a tied cell, associated with the minimum and unique batch compatibility number, as a tiebreak winner.
8. The method of claim 6 , wherein breaking the tie between the plurality of tied cells further comprises:
globally uniquifying the set of compatible cells to obtain a plurality of uniquified sets of compatible cells by removing duplicate cells that appear more than once within each set of compatible cells;
identifying the batch compatibility number for the plurality of uniquified sets of compatible cells; and
selecting a cell with lowest batch compatibility number among the compatible cells for each tied cell in the plurality of uniquified sets of compatible cells.
9. The method of claim 1 , further comprising:
sorting the plurality of cells according to the batch compatibility numbers in order to obtain a sorted list of cells; and
evaluating the plurality of cells according to the batch compatibility numbers beginning with a cell with a lowest or highest batch compatibility number.
10. The method of claim 1 , wherein the plurality of cells are from a same manufacturing run.
11. A battery formed according to the method of claim 1 .
12. A method, comprising:
providing a plurality of cells associated with a plurality of cell characteristics;
identifying, among the plurality of cells, a first cell with a batch compatibility number indicative of one or more cell characteristics associated with the first cell, wherein the batch compatibility number indicates a number of compatible cells with the first cell;
identifying, among the plurality of cells excluding the first cell, a second cell with a same batch compatibility number as the first cell; and
assembling a battery by including at least the first cell and the second cell in the battery.
13. The method recited in claim 12 , wherein the plurality of cell characteristics includes one of more of: a capacity, an open circuit voltage, a resistance, or a self-discharge rate.
14. The method recited in claim 12 , further comprising:
generating a cell compatibility matrix which indicates, for the plurality of cells, whether a given pair of cells is compatible.
15. The method recited in claim 12 , further comprising:
determining a first difference between the first cell and the second cell a first cell characteristic;
determining a second difference between the first cell and the second cell for a second cell characteristic; and
when (1) the first difference does not exceed a first tolerance associated with the first cell characteristic and (2) the second difference does not exceed a second tolerance associated with the second cell characteristic, declaring the first cell and the second cell to be compatible.
16. The method recited in claim 12 , further comprising:
determining, for each tied cell in a plurality of tied cells, a set of compatible cells in order to obtain a plurality of sets of compatible cells; and
breaking a tie between the plurality of tied cells based at least in part on uniqueness associated with the plurality of sets of compatible cells and one or more batch compatibility numbers associated with the plurality of sets of compatible cells.
17. The method recited in claim 16 , wherein breaking the tie between the plurality of tied cells comprises:
sorting the plurality of sets of compatible cells based at least in part on the batch compatibility numbers associated with the plurality of sets of compatible cells to obtain a plurality of sorted lists of compatible cells;
selecting two or more compatible cells to compare from different sorted lists of compatible cells, wherein the selected compatible cells are at a same level in their respective sorted lists of compatible cells; and
when a minimum batch compatibility number, associated with the selected compatible cells to compare, is unique, selecting a tied cell, associated with the minimum and unique batch compatibility number, as a tiebreak winner.
18. The method of claim 16 , wherein breaking the tie between the plurality of tied cells further comprises:
globally uniquifying the set of compatible cells to obtain a plurality of uniquified sets of compatible cells by removing duplicate cells that appear more than once within each set of compatible cells;
identifying the batch compatibility number for the plurality of uniquified sets of compatible cells; and
selecting a cell with lowest batch compatibility number among the compatible cells for each tied cell in the plurality of uniquified sets of compatible cells.
19. The method of claim 12 , further comprising:
sorting the plurality of cells according to the batch compatibility numbers in order to obtain a sorted list of cells; and
evaluating the plurality of cells according to the batch compatibility numbers beginning with a cell with a lowest or highest batch compatibility number.
20. A battery formed according to the method of claim 12 .