The BT2152B Self-Discharge Analyzer can measure the self-discharge current of lithium-ion cells, enabling faster differentiation of cell self-discharge performance, thereby significantly reducing work-in-process inventory in cell manufacturing.

Features

• The number of self-discharge current measurement channels can be increased by 4 at a time, up to a maximum of 32 channels

• Cell voltage range: 0.5 to +4.5 V

• Current measurement accuracy: ± (0.30% + 250 nA)

• Voltage measurement accuracy: ± (0.04% + 0.1 mV)

• Voltage source stability: ± 3 μV peak (24 hours), ± 0.85 μV peak (1 minute)

• Current range: ± 10 mA

The Keysight BT2152B Self-Discharge Analyzer can directly measure the self-discharge current of lithium-ion cells and significantly accelerate the differentiation of cell self-discharge performance, thereby greatly reducing work-in-process inventory, operating capital costs, and facility expenses for cell manufacturers.

The self-discharge analyzer can accurately measure the self-discharge current and voltage of cells. Depending on the characteristics of the cell, the measurement can be completed in just a few minutes or hours, unlike the traditional method which took days or weeks to distinguish cell quality by measuring open-circuit cell voltage.

This self-discharge analyzer is equipped with various features necessary for accurate current measurement and can quickly measure self-discharge current using precise potentiostatic measurement techniques.

• Minimize interference with the cell

  • The voltage applied to the cell quickly matches the actual cell voltage. This minimizes new charging or discharging, thereby shortening the new RC settling time.

  • The voltage applied to the cell is highly stable (± 3 μVpk), minimizing the impact of self-discharge current noise on discharge current measurement.

• Measurement accuracy for low-level self-discharge current: ±(0.30% + 250 nA)

Improving the Self-Discharge Testing Process and Saving Costs

Lithium-ion cell manufacturers hold far more work-in-process inventory than anticipated due to the need for cell aging tests.

Currently, the time required to determine whether a cell's self-discharge characteristics are within acceptable limits accounts for a significant portion of the overall aging time. This period is typically long and is primarily determined by the time needed to measure OCV changes (ΔOCV). Reducing the time cells spend in work-in-process inventory during aging can save costs and directly increase profitability.

By examining typical models of the formation and aging processes in cell manufacturing and comparing the direct measurement of cell self-discharge current with the traditional OCV method, it is evident that the direct self-discharge current measurement method helps improve the aging process and save costs.

Traditional ΔOCV Method

Determining cell self-discharge performance involves two steps. The first step, after a 5-day aging period, involves performing a ΔOCV test to separate cells with clearly distinguishable performance from "suspicious" cells, where ΔOCV = OCV2 – OCV1. The "suspicious" cells then undergo a longer aging period, followed by another ΔOCV test, where ΔOCV = OCV3 – OCV2. Most cells require only a short aging time, but some "suspicious" cells require a much longer aging period to determine whether their self-discharge characteristics are within acceptable limits.

Direct Measurement of Self-Discharge Current

This method of determining cell self-discharge performance also involves two steps. The first step is the same as the ΔOCV test, where ΔOCV = OCV2 – OCV1. Then, the self-discharge of "suspicious" cells is directly measured. While the traditional aging test for "suspicious" cells typically takes at least 4 weeks, direct measurement requires less than about 1 hour.

If 10% of the produced cells are classified as "suspicious" and require further testing or aging after the initial ΔOCV test, the direct self-discharge measurement method reduces the overall time by approximately 81% (7 days vs. 37 days) compared to the aging test method. By eliminating the lengthy aging step for "suspicious" cells, the direct measurement method can reduce the total number of cells in aging tests by 30%. This directly lowers the requirements for work-in-process inventory and facilities.

You can download a cost-saving model for operating capital costs and facility costs to compare the ΔOCV method with the direct self-discharge measurement (SDM) method. This model is created using Microsoft Excel, and the worksheet is provided below for you to download and modify to ensure it fits the actual conditions of each type of cell you manufacture.