CALCE CS2 · voltage-shape matrix

Four batteries of the same type, each a single 1.1 Ah lithium-cobalt-oxide prismatic cell, were repeatedly charged by a constant-current/constant-voltage protocol and discharged at room temperature from 2010-08-16 to 2011-02-03.

This page follows the data from the cycler to the voltage-shape matrix: what was measured, what the cycler wrote, and how 1,119,328 logged samples become a 3,245 × 128 matrix of voltage-curve shapes. The same raw data also feeds a second feature set, the SOH series, which has its own Dataset page.

Each battery sat on its own channel of an Arbin battery tester and was cycled under one repeating schedule. CALCE documents the charge as constant current at 0.5 C until 4.2 V, then 4.2 V held until the current falls below 0.05 A, and a constant-current discharge to a 2.7 V cut-off. The logs show the same schedule for all four batteries: about +0.55 A during constant-current charge and −1.1 A (1 C) during discharge.

From the test bench to this page

1. DocumentedTest bench (CALCE)

   Four 1.1 Ah lithium-cobalt-oxide batteries on an Arbin tester, CC–CV cycling from 2010-08-16 to 2011-02-03

2. HeldRaw workbooks

   4 archives, 106 workbooks, 1,119,328 samples

3. ReproducedCurve-shape recipe

   Screen, resample 64 + 64 points, standardise within the row; rerun here

4. ReproducedShape matrix

   3,245 × 128, built here from the raw workbooks

Documented: described by CALCE, not rerun here. Reproduced: rerun here on the raw workbooks. Held: the bytes this page reads.

The basic unit: one cycle

A cycle is one charge followed by one discharge, with rests in between. The figure shows one early cycle of CS2_35, exactly as logged.

Two panels share one time axis. Current is positive while charging and negative while discharging.

What each sample records

Samples arrive about every 30 s, further apart while the voltage is held at 4.2 V. Later workbooks also carry a per-cycle Statistics sheet.

A workbook, opened

The first rows of the data sheet in CS2_35_10_15_10.xlsx (battery CS2_35): one row per logged sample.

One workbook as a signal

The same workbook holds 50 cycles and 17,139 samples, starting 2010-10-08 14:29. Its first 48 hours are drawn; every tooth is one charge/discharge cycle.

How the workbooks cover each battery’s life

Each bar is one workbook, placed by the timestamps inside it. Hover for the file name and contents.

What the raw record does not give you directly

• Cycle numbers restart in every workbook. A cycle count across a battery’s life has to be built by offsetting each file.
• File names carry the export date, not the data date. CS2_35_10_15_10.xlsx starts on 2010-10-08. Files must be ordered by their first timestamp.
• 2 workbooks are duplicate final exports (CS2_35_2_4_11.xlsx, CS2_38_2_4_11.xlsx): different files holding the same samples.
• Capacity columns are cumulative within a workbook, so a cycle’s capacity is a difference, not a value.
• Not every logged cycle is a complete, on-protocol cycle. Interrupted, resumed and sparsely logged cycles sit in the same sheets.

The curve-shape recipe keeps the full shape of each cycle and removes its level, scale and duration, so that only the shape remains. Each step below runs on the raw workbooks described above.

Where the cycles go

Follow one cycle

Pick a cycle to see it at each step, from the samples the cycler wrote to the row the matrix stores. Dropped cycles stop at the step that rejects them.

Features

Labels kept beside the matrix

• One retained row, CS2_36 cycle 265, has coulombic efficiency 3.3147: a partial or resumed charge passes the endpoint, current and gap screens.
• The heatmap is a display copy clipped at |z| = 4.2 and stored at 8-bit precision; statistics use the full-precision matrix.
• Cycle numbers are built by offsetting each workbook, so they count logged cycles, not cycles since the batteries were new.

Battery curve-shape explorer: PCA of curve shape, per battery and with one battery left out; and its Key Findings page.