Underling data for "The Battery Life Estimation of a Battery under Different Stress Conditions"

Each file reports the capacity trend as a function of the number of cycles, for NMC cells aged according to different protocols, as reported in the following table:

Test Number

Discharge Current (C-Rate)

ΔSOC = SOCin − SOCfin

Cycle between Control Tests

1

1 C

80−20

200

2

2 C

80−20

200

3

3 C

80−20

100 1

4

5 C

80−20

100

5

1 C

90−10

160

6

1 C

70−30

320

7

5 C

70−30

320

8

3 C

90−10

160  

9

8 ×   3C@80%DOD + 10  × 2C@40%DOD

90−10, 70−30

90

The number of the file corrrespond to the test number (e.g. B1 referers to results for a cell undergone test 1). Cells tested where 20 Ah EIG NMC-graphite.

In order to compare the results for cells subjected to life tests with different ΔSOCs, it is necessary to appropriately quantize the cumulative charge, to obtain a suitably defined equivalent cycle. To this end, we consider the greatest common factor (GCF) among ΔSOCs. We then define the number of equivalent cycles (ECs) of each life test as the ratio between the ΔSOC value and GCF. In our case, we considered 3 ΔSOC: 40%, 60%, and 80%. The GCF is therefore 20%. Hence, the number of EC equals 2, 3, and 4 for each cycle at ΔSOC 40, 60, and 80%, respectively. Obviously, this is not the only quantization possible, but a different choice does not affect the validity of the model, as long as the transformation is linear, although it would lead to different results for the parameters.

The capacity has been evaluated with a standard charge-discharge cycle at 0.5C rate, after a given number of test cycles, as reported in the files. All files are structured as follows:

Column number
1
2
3

Field description
Number of cycles
Number of equivalrent cycles
Relative capacity

Relative capacity: ratio between the capacity value after N cycle and the capacity value at the beginning of life.