Dear all,
This morning I plot the Cell A of the past week and I see three different battery discharge slope during evening pass over Jakarta (around 14:00 - 16:30 UTC)
The leftmost blue line in gray background shows normal discharge during evening pass, followed by slightly steeper decline that tripped the satellite into Safe mode just before TCA over me in Jakarta. The rightmost decline was from last night (16:23 UTC 7 Dec pass) that shows an even steeper decline. This is very discouraging in my opinion.
So, to prevent further deterioration of this cell, would it be possible to command “put into Safe Mode if in Eclipsed” ?
Use the sun sensor to determine sunlight.
73 de Yono - YD0NXX Jakarta, Indonesia - OI33JR
Sent from my iPhone
On Dec 8, 2020, at 11:33 AM, John Brier [email protected] 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 [email protected] 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-...
73,
Paul, N8HM
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