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NOTE: This guide serves as documentation for the tests that were conducted on the cells, not as the best way to do these tests in the future. The best way to get controlled cell data is to measure cells using an Source Measurement Unit which supports charging and discharging so we can control the amount of rest time in between charge and discharge, as I believe this had a large effect on some of the results. Automated test procedures can also be developed which will greatly reduce testing time.

In order to select the best cells for MSXIV, lots of testing must be completed to properly characterize the cells. We want to use the safest, highest energy cells in order to maximize the capacity of our battery pack. Several new cells have come out since MSXII and are looking promising based on online reviews, so we will be doing a comprehensive test of the best cells on the market.

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• We will be using strips of MSXII’s busbars to connect the cells in the 4P configurations.
• For the single cell initial tests, we will use a removable system - clamping the cells in so we don’t ruin the potential to spot weld cells later (spot welding twice to a cell does not work well, as once the original tab is removed, the top is no longer flat, making it harder to get a good spot weld). This will be done using dimpled copper strips, and some kind of clamping mechanism to hold it in place.
• For the multi-cell tests, we will use extra copper busbars from MSXII and have the mainspot weld 4 cells together using nickel strips soldered to these copper plates.

Measuring Internal Resistance:

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1. Charge the cells using either a DC power supply set to 4.2V, 1.0A, and monitor it until the current reaches under 100mA - OR - Use the iCharger 306B on a 1S LiPo setting at 1A.
2. Use the iCharger 306B to measure internal resistance of the cells – it is one of the preconfigured tests.
3. Update the result in the spreadsheet

A resistance of the probed probes used to connect to the battery must also be measured so that we can measure the actual internal resistance of the cells, and not including the resistance of the cables.

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For the test conditions down the left side apply the following settings:

There are other ways to discharge test a cell, but for capacity measurement, we are going with this method.

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Get the data from the multimeter by connecting over Ethernet and copy the data to Excel or to a text file. See this video for details: https://www.youtube.com/watch?v=8MZHP6gKcOU. The video makes it look extremely easy, but it really isn't (at least nowadays).

After a few hours of trying different configurations, I got it to work using Internet Explorer,   having Java RE 7u79 installed (the web applet uses java), and bypassing all the security features that prevent an old version of java from running (https://www.math.ucsd.edu/~crypto/fixjava.html). Since updating the firmware, it now works with Java 8.

The above is a method that I have found that works, although there might be easier methods. Keysight creates a software called BenchVue that advertises that it is able to connect to and control the Agilent 34410A multimeter. I have not tested it yet, but it is costly software.

A Note for 4P Tests

The cells get connected to the constant current load via the 12AWG cables and M3 nuts and bolts.

VERY IMPORTANT - Charge procedure for the tested cells:

1. Charge 4P pack at 4.2V, with 4A constant current
2. When current falls to 300mA, remove from charger
3. Wait 30 minutes for voltage to settle, then start discharge test

Cell wrapping: For all 4P tests, the module is to be wrapped in blue tape in order to remove the cooling effects of circulating air. The blue tape should be attached to the black holders, and should not be touching the cells directly.

Testing a Cell

How to test a cell:

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