Just one comment:  Other than AO-91, (and upcoming Fox-1E) we had no telemetry to indicate whether a single battery pair was failing or if they failed "together".  Only AO-91 had individual cell pair telemetry.  (Pair:  There were 6 cells, 2 parallel cells in a 3-series chain).

The 5-year prediction was made before my time at AMSAT.  But I do know that the original plan (after AO-51 and for that matter 7) failed, was to design the power system so that if the batteries shorted, we would still run on solar panels.  Many of you may have heard that said.  But the launch time approached fast before such a design could be realized.  And in fact despite the seemingly long times between some launches, the times when we had to be "hands off" on birds was too close to make many changes based on past experience.  And of course the first one to go (AO-85) failed long after all the other 4 were either in orbit or frozen.

Burns, WB1FJ

On Mon, Dec 7, 2020 at 3:13 PM John Brier <johnbrier@gmail.com> wrote:
Thank you very much Paul.

I must have missed that during the Symposium.

So overall, do you think the time the satellites were in eclipse and
in use was longer than expected?

Otherwise what would explain the higher than planned depth of discharge?

73, John Brier KG4AKV

P.S.

For anyone else looking through the PDF mentioned earlier, the cells
mentioned on page 324 were 6x SANYO KR1700AU "A" CELLS, which
apparently didn't end up being the actual used cells, as Paul
mentioned

On Mon, Dec 7, 2020 at 2:59 PM Paul Stoetzer <n8hm@arrl.net> wrote:
>
> Each Fox-1 satellite uses 6 Sanyo KR-1400AE NiCd A cells.
>
> Obviously we all hoped that the batteries would last a lot longer. As
> discussed during the Symposium, the likely cause of battery failure is
> a higher than planned depth of discharge. Note that AO-92's batteries
> failed more quickly than AO-91. Since AO-92's evening passes were
> generally between 9 and 11 pm, AO-92 saw lots of use while in ecilpse.
> Contrast that to AO-91, where the evening passes were generally after
> midnight, so it saw less use while in eclipse.
>
> I'm not sure there's much to be learned from the experience with these
> batteries as NiCd battery technology is now certainly obsolete and
> will not be used in future AMSAT satellites. AMSAT's GOLF series of
> satellites will use lithium ion batteries. More information about the
> progress of GOLF, including the GOLF-TEE status paper from the 2020
> Symposium Proceedings, can be found at
> https://www.amsat.org/greater-orbit-larger-footprint-an-introduction-to-the-amsat-golf-program/
>
> 73,
>
> Paul, N8HM
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