Open battery ageing data · CALCE CS2
CALCE CS2 battery ageing data: 15 LiCoO2 cells, cycle by cycle
The Center for Advanced Life Cycle Engineering (CALCE) at the University of Maryland cycled 15 prismatic LiCoO2 cells of 1.1 Ah, its CS2 cells, in six test types: constant discharge at 0.5C or 1C, discharge currents that change from cycle to cycle, a randomly moved cut-off voltage, and two partial voltage windows. Lemonergy computed one row of values per charge-discharge cycle from CALCE’s files. CALCE states no licence, so its files are not copied here; the computed values are, with the citation CALCE asks for.
- Cells
- 15 prismatic cells (maker not stated)
- Chemistry
- LiCoO2 (LCO)
- Nominal capacity
- 1.1 Ah
- Cycles
- 35,424, one row each
- Test programmes
- 6
- Published by
- Center for Advanced Life Cycle Engineering, U. Maryland
- Licence
- None stated: computed values only, published with the citation the publisher asks for; the files are not copied
- Files retrieved
- 2026-10-29
Download every cycle (CSV)Chart and Excel downloadManifest: files, hashes, unitsOriginal dataset
Capacity fade, cycle by cycle
Discharge capacity per cycle, one coloured line per cell, one discharge rate per line. Point at a chart to read the values; download them as Excel.
The chart needs JavaScript; every cell’s values are in the table below and in the CSV.
Point at or touch a chart to read every cell’s value at that cycle. Drag across it with a mouse to zoom in. Select a cell in the legend to hide or show it.
| Cell | Cycles run | Points drawn | First (Ah) | Last (Ah) | Last / first |
|---|
Every cell
First and last discharge capacity of the cycles the chart draws, for all 15 cells. Every cycle of every cell, with all its values, is in the CSV.
| Programme | Cell | Cycles run | Points drawn | First (Ah) | Last (Ah) | Last / first |
|---|---|---|---|---|---|---|
| Type 1 | CS2_8 | 725 | 247 | 1.127 | 0.889 | 78.9 % |
| Type 1 | CS2_21 | 499 | 143 | 1.090 | 0.887 | 81.4 % |
| Type 1 | CS2_33 | 866 | 862 | 1.162 | 0.059 | 5.1 % |
| Type 1 | CS2_34 | 777 | 773 | 1.154 | 0.516 | 44.7 % |
| Type 2 | CS2_35 | 882 | 880 | 1.139 | 0.304 | 26.7 % |
| Type 2 | CS2_36 | 973 | 970 | 1.145 | 0.172 | 15.1 % |
| Type 2 | CS2_37 | 1,038 | 1,036 | 1.135 | 0.191 | 16.8 % |
| Type 2 | CS2_38 | 1,028 | 1,025 | 1.139 | 0.290 | 25.4 % |
| Type 4 | CS2_7 | 1,118 | 102 | 1.137 | 0.397 | 34.9 % |
| Type 3 | CS2_3 | 1,361 | not drawn | – | – | – |
| Type 3 | CS2_9 | 1,181 | not drawn | – | – | – |
| Type 5 | CS2_5 | 7,020 | not drawn | – | – | – |
| Type 5 | CS2_6 | 6,307 | not drawn | – | – | – |
| Type 6 | CS2_24 | 5,039 | not drawn | – | – | – |
| Type 6 | CS2_25 | 6,610 | not drawn | – | – | – |
Test programmes
- Type 1. CS2_8, CS2_21, CS2_33 and CS2_34: discharged at a constant 0.5C (0.55 A). Drawn: 0.5C discharge, full cycles.
- Type 2. CS2_35 to CS2_38: discharged at a constant 1C (1.1 A). Drawn: 1C discharge, full cycles.
- Type 4. CS2_7: discharged at 0.55 A, with the cut-off voltage changed at random times, as a user might stop at an unpredictable voltage. Drawn: 0.55 A discharge, the full cycles among varied cut-offs.
- Type 3. CS2_3 and CS2_9: constant-current discharge whose current changes from cycle to cycle among 0.11, 0.22, 0.55, 1.1, 1.65 and 2.2 A. Not drawn: the discharge current changes every cycle, so a line would mix six rates; its cycles are in the CSV.
- Type 5. CS2_5 and CS2_6: one full charge and a full discharge at 0.22 A, then cycled between 3.77 V and 2.7 V, discharging at 0.55 A. Not drawn: cycled between 3.77 V and 2.7 V; the rate of its few full cycles is not stated; its cycles are in the CSV.
- Type 6. CS2_24 and CS2_25: one full charge and a full discharge at 0.22 A, then cycled between 4.2 V and 3.77 V, discharging at 0.55 A. Not drawn: cycled between 4.2 V and 3.77 V; the rate of its few full cycles is not stated; its cycles are in the CSV.
The programmes are grouped as the publisher’s page groups them (read 2026-10-30), in our words.
Columns of the CSV
Each cell's session files (Arbin .xlsx or CADEX .txt) merged with battery-data tools/convert_calce_cs2.py and its cycles computed with tools/cyclers.py (cycle = one charge followed by one discharge; capacity integrated from current) at battery-data 5d881c9: the cycle_summary rows of the CALCE import. Values are rounded as printed: Ah and volts to 4 decimals, efficiency to 5, seconds to 0.1.
| Column | Unit | Meaning |
|---|---|---|
cell | – | CALCE cell name |
cycle | – | cycle number, 1-based, counted by battery-data |
charge_ah | Ah | charge capacity integrated from current |
discharge_ah | Ah | discharge capacity integrated from current |
coulombic_efficiency | – | discharge_ah / charge_ah (meaningless when charge_ah is near zero) |
v_max | V | highest voltage in the cycle |
v_min | V | lowest voltage in the cycle |
duration_s | s | length of the cycle |
start_test_time_s | s | start of the cycle on the cell's merged time axis |
Before comparing cells
- CS2_3 (12-18 October 2012) and CS2_25 (4-5 March 2013) each hold two different recordings of the same period; the session that starts first is kept and the overlapping rows of the other dropped. CALCE was asked on 30 October 2026 which is correct.
- CS2_8 and CS2_21 were tested on a CADEX tester whose files carry no clock: their sessions are joined end to end, so the gaps between sessions are unknown and start times are not calendar times.
- CS2_3 and CS2_9 use stepped discharge currents; the tester counts cycles by its own schedule (863 and 204), battery-data by charge-discharge pairs (1,361 and 1,181).
- Rests, short top-ups and other partial cycles are rows too. A full cycle charges to 4.2 V and discharges to the 2.7 V cut-off (v_max at or above 4.15 V and v_min at or below 2.75 V); v_min alone is not enough, because Type 5 cells reach 2.7 V every cycle from 3.77 V.
- CS2_8 cycle 574 and CS2_21 cycle 425 each hold two charges and one discharge, because the CADEX recording has no discharge between the two charges; their charge_ah and coulombic_efficiency are not a normal cycle's (see exceptions).
- Most downward spikes are single cycles whose charge and discharge are both smaller than their neighbours' (coulombic efficiency stays near 1); they are drawn as recorded.
Licence and how to cite
The publisher states no licence. Its files are therefore not copied here; the values Lemonergy computed from them are published with the citation it asks for, and are withdrawn if it asks. Fetch the files themselves from the publisher.
Cite: He, W., Williard, N., Osterman, M., Pecht, M. Prognostics of lithium-ion batteries based on Dempster-Shafer theory and the Bayesian Monte Carlo method. Journal of Power Sources 196(23), 10314-10321 (2011). Also cited by CALCE for CS2: Xing et al., Microelectronics Reliability 53(6), 811-820 (2013); Williard et al., Int. J. Prognostics and Health Management 4, 1-7 (2013).
Credit: Data: CALCE Battery Research Group, University of Maryland (calce.umd.edu/battery-data), CS2 cells; cite He, Williard, Osterman and Pecht, J. Power Sources 196 (2011) 10314-10321, as CALCE asks. Per-cycle values computed by Lemonergy (battery-data).
Values pinned to battery-data revision 55c1ff5, with every source file named by its SHA-256 in the manifest.