NiCd Battery Analysis: Historical and Modern

Greetings all!

I’d like to tell you all about a project going on to revive/document Larry Keyser’s engineering on matched NiCd cells that made up the batteries for UO-11 and other amateur payloads from that era. This would be up to four of the AO-teens payloads, and at least one other smallsat. The batteries were very reliable, exceeding amateur and professional expectations. 

Selecting cells for a battery takes testing and an understanding of the basics of the underlying chemistry and physics. Early amateur payloads got a great deal here with some surplus cells from avionics and/or medical surplus. These cells were high quality to begin with, but that’s not enough by itself to ensure a lengthy lifespan in space. 

Larry Keyser knew how to match the cells to make batteries that would last a long time. The overall strategy was to select batteries that were similar. Not necessarily the best performers in the batch, but the best matched cells.

Temperature performance and curve matching were both considered critical. Furthermore, the batteries were scanned to eliminate those with internal structural anomalies and faults. 

Several of us at ORI are preserving, publishing, and extending this work. We have some advantages, in that modern battery analysis equipment is much easier to use and more capable than what previous volunteers had to work with. ORI has a modern battery analyzer, capable of working up to 44 volts, available for community use.

Modern test equipment produces much higher resolution charge/discharge curves, and temperature monitoring is incorporated automatically. Measurements can be automated in ways that Larry didn’t really have available at the time he was working on this for AMSAT and other missions. 

We have software tools and languages (Python, MATLAB) that make curve matching easier. There’s never been a better time to save and publish a summary article about Larry’s achievements and what we, as modern hams, can do to improve upon it. 

This is all open source work through Open Research Institute. It’s offered for free to anyone or any organization that wants to use it. NiCd batteries aren’t as hip or cool as Lithium Ion, but they are reliable in space, and this ongoing battery project will produce both data and actual physical battery packs that amateur/educational missions may want to consider using. 

The battery analysis equipment is capable of doing any battery chemistry, so if you have an open source amateur satellite project in mind that needs battery analysis support, ORI is here to help out with that. 

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