In an earlier posting “The Value of Measuring Self-Discharge on Lithium Ion Cells” (click here to review) I explained what measuring self-discharge on LiIon cells is all about. I also introduced two new solutions for measuring self-discharge, from Keysight. These solutions use a proprietary approach that directly measures the self-discharge current of the cells in the matter of hours or less, instead of traditional approach of monitoring the cells’ open circuit voltage loss over weeks of time, to infer what the self-discharge is.
The first solution introduced is the BT2191A Self-Discharge Measurement System, shown in Figure 1. It is ready-to-use single-channel solution for evaluating and analyzing self-discharge current on Li-Ion cells. It is primarily intended for R&D engineers who are evaluating new Li-Ion cell designs and impact of design changes during development. A necessary and integral part of the BT2191A is its BT2192A Self-Discharge Measurement System Software. The BT2192A is integral because it integrates several pieces of standard test equipment into a specialized solution. A big advantage of the BT2192A software is it saves time and effort by providing a very convenient way to set up, capture, display, analyze, store, and recall self-discharge measurement results, without having to resort to any programming.
Figure 1: BT2191A Self-Discharge Measurement System
The second solution introduced is the BT2152A Self-Discharge Analyzer, shown in Figure 2. The BT2152A is a one-box 32-channel solution for testing self-discharge on a much larger number of Li-Ion cells in manufacturing. The BT2152A was designed from the ground up specifically for this purpose, so separate software comparable to the BT2192A is not required to make the BT2152A a working solution for self-discharge measurement. Typically, several BT2152A’s are incorporated into a test system and code for automated self-discharge testing in manufacturing is developed by the manufacturer to be compatible with their existing systems. To ease this programming task the BT2152A Self-Discharge Analyzer has a simplified command set specifically for making self-discharge measurements. This greatly reduces the effort required for developing dedicated test code for automating self-discharge testing.
Figure 2: BT2152A Self-Discharge Analyzer
However, one situation where it would be especially advantageous to have ready-to-run software is performing initial evaluations on the BT2152A for self-discharge on Li-Ion cells. To address this, Keysight has recently introduced the BT2155A Self-Discharge Analysis Software. Now a test engineer can immediately start conducting evaluations using the BT2152A, without having to spend time up-front to create a test program. The BT2155A’s graphical user interface is shown in Figure 3.
Figure 3: BT2155A Self-Discharge Analysis Software for the BT2152A Self-Discharge Analyzer
Just a few the many features of the BT2155A user interface shown in Figure 3 include:
- Access to several pull-up menus to set up instrument addresses, data formatting preferences, external fixture wiring calibration, and more.
- Setup test parameters.
- Setup test parameters specific to each of the individual test channels.
- Test execution messages window, including information, warnings, and errors.
- Temperature of cells over duration of test measurement logging.
- Voltages and self-discharge currents of cells over duration of test measurement logging.
In this example in Figure 3, after about 4.5 hours’ test/settling time, eight 2.4 Ah Li-Ion cells were found to range from 8 to 12 micro amperes of self-discharge current. This is much faster than the weeks of time needed for the traditional inferred approach of measuring a significant amount of cell open circuit voltage loss due to self-discharge.
If evaluating self-discharge of Li-Ion cells is relevant to your work, the BT2155A software should be of interest to you. You now have a turn-key solution for evaluating self-discharge of large number of Li-Ion cells when it is paired with the BT2152A Self-Discharge Analyzer. Check out the Keysight home pages for the new BT2155A Self-Discharge Analysis Software (click here to access) and BT2152A Self-Discharge Analyzer (click here to access) to learn more about self-discharge measurements and these solutions. There you will find application notes, data sheets, evaluation guides, and more to help you out.