Li-ion Battery Aging Datasets

This data set has been collected from a custom built battery prognostics testbed at the NASA Ames Prognostics Center of Excellence (PCoE). Li-ion batteries were run through 3 different operational profiles (charge, discharge and Electrochemical Impedance Spectroscopy) at different temperatures. Discharges were carried out at different current load levels until the battery voltage fell to preset voltage thresholds. Some of these thresholds were lower than that recommended by the OEM (2.7 V) in order to induce deep discharge aging effects. Repeated charge and discharge cycles result in accelerated aging of the batteries. The experiments were stopped when the batteries reached the end-of-life (EOL) criteria of 30% fade in rated capacity (from 2 Ah to 1.4 Ah). **Data Acquisition:** The testbed comprises: * Commercially available Li-ion 18650 sized rechargeable batteries, * Programmable 4-channel DC electronic load, * Programmable 4-channel DC power supply, * Voltmeter, ammeter and thermocouple sensor suite, * Custom EIS equipment, * Environmental chamber to impose various operational conditions, * PXI chassis based DAQ and experiment control, and MATLAB based experiment control, data acquisition and prognostics algorithm evaluation setup (appx. data acquisition rate is 10Hz). **Parameter Description:** Data Structure: cycle: top level structure array containing the charge, discharge and impedance operations type: operation type, can be charge, discharge or impedance ambient_temperature: ambient temperature (degree C) time: the date and time of the start of the cycle, in MATLAB date vector format data: data structure containing the measurements for charge the fields are: Voltage_measured: Battery terminal voltage (Volts) Current_measured: Battery output current (Amps) Temperature_measured: Battery temperature (degree C) Current_charge: Current measured at charger (Amps) Voltage_charge: Voltage measured at charger (Volts) Time: Time vector for the cycle (secs) for discharge the fields are: Voltage_measured: Battery terminal voltage (Volts) Current_measured: Battery output current (Amps) Temperature_measured: Battery temperature (degree C) Current_charge: Current measured at load (Amps) Voltage_charge: Voltage measured at load (Volts) Time: Time vector for the cycle (secs) Capacity: Battery capacity (Ahr) for discharge till 2.7V for impedance the fields are: Sense_current: Current in sense branch (Amps) Battery_current: Current in battery branch (Amps) Current_ratio: Ratio of the above currents Battery_impedance: Battery impedance (Ohms) computed from raw data Rectified_impedance: Calibrated and smoothed battery impedance (Ohms) Re: Estimated electrolyte resistance (Ohms) Rct: Estimated charge transfer resistance (Ohms) **Intended Use:** The data sets can serve for a variety of purposes. Because these are essentially a large number of Run-to-Failure time series, the data can be set for development of prognostic algorithms. In particular, due to the differences in depth-of-discharge (DOD), the duration of rest periods and intrinsic variability, no two cells have the same state-of-life (SOL) at the same cycle index. The aim is to be able to manage this uncertainty, which is representative of actual usage, and make reliable predictions of Remaining Useful Life (RUL) in both the End-of-Discharge (EOD) and End-of-Life (EOL) contexts.

本数据集采集自美国国家航空航天局艾姆斯研究中心（NASA Ames）卓越预测科学中心（Prognostics Center of Excellence, PCoE）定制搭建的电池预后测试平台。锂离子电池在不同温度下，历经三种不同的运行工况：充电、放电与电化学阻抗谱（Electrochemical Impedance Spectroscopy, EIS）测试。放电环节以不同的电流负载等级执行，直至电池电压降至预设阈值；部分阈值低于原厂（Original Equipment Manufacturer, OEM）推荐的2.7V，以诱发深度放电老化效应。反复的充放电循环会加速电池老化，实验直至电池容量衰减至额定容量的30%（即从2Ah降至1.4Ah），达到寿命终止（End-of-Life, EOL）标准后停止。

**数据采集：** 该测试平台包含以下组件：
* 商用18650型锂离子（Li-ion）可充电电池；
* 可编程4通道直流电子负载；
* 可编程4通道直流电源；
* 电压表、电流表与热电偶传感器套件；
* 定制化电化学阻抗谱设备；
* 用于模拟不同运行环境的环境试验箱；
* 基于PXI机箱的数据采集（Data Acquisition, DAQ）与实验控制系统，以及基于MATLAB的实验控制、数据采集及预后算法评估平台（数据采集速率约为10Hz）。

**参数说明：**
数据结构如下：
- `cycle`：顶层结构数组，涵盖充电、放电与阻抗测试三类操作
- `type`：操作类型，可选值为charge（充电）、discharge（放电）或impedance（阻抗测试）
- `ambient_temperature`：环境温度（单位：摄氏度）
- `time`：循环开始的日期与时间，采用MATLAB日期向量格式
- `data`：包含对应操作测量数据的结构数组，各操作对应的字段如下：
1. 充电操作字段：
- `Voltage_measured`：电池端电压（单位：伏特）
- `Current_measured`：电池输出电流（单位：安培）
- `Temperature_measured`：电池温度（单位：摄氏度）
- `Current_charge`：充电器侧测得的电流（单位：安培）
- `Voltage_charge`：充电器侧测得的电压（单位：伏特）
- `Time`：循环时长向量（单位：秒）
2. 放电操作字段：
- `Voltage_measured`：电池端电压（单位：伏特）
- `Current_measured`：电池输出电流（单位：安培）
- `Temperature_measured`：电池温度（单位：摄氏度）
- `Current_charge`：负载侧测得的电流（单位：安培）
- `Voltage_charge`：负载侧测得的电压（单位：伏特）
- `Time`：循环时长向量（单位：秒）
- `Capacity`：放电至2.7V时测得的电池容量（单位：安时）
3. 阻抗测试操作字段：
- `Sense_current`：采样支路电流（单位：安培）
- `Battery_current`：电池支路电流（单位：安培）
- `Current_ratio`：上述两路电流的比值
- `Battery_impedance`：由原始数据计算得到的电池阻抗（单位：欧姆）
- `Rectified_impedance`：经过校准与平滑处理的电池阻抗（单位：欧姆）
- `Re`：估算得到的电解液内阻（单位：欧姆）
- `Rct`：估算得到的电荷转移阻抗（单位：欧姆）

**预期用途：** 本数据集可应用于多种科研与工程场景。由于其本质为大量“运行至失效”的时间序列数据，可用于开发电池预后算法。特别地，由于放电深度（Depth-of-Discharge, DOD）、静置时长以及电池本征差异性的不同，任意两节电池在相同循环次数下的寿命状态（State-of-Life, SOL）均不相同。本数据集旨在帮助研究者应对这类贴合实际使用场景的不确定性，实现在放电终止（End-of-Discharge, EOD）与寿命终止（EOL）场景下对剩余使用寿命（Remaining Useful Life, RUL）的可靠预测。