On 08/14/2011 10:18 PM, Anthony Monteiro AA2TX wrote:
This is speculation but it looks to me like we
have had a bit of good luck regarding the battery.
Looking at the battery voltage from deployment on…
Up until Aug 11, the battery seems to be deteriorating “normally” with a slight downtrend in the max voltage as expected. But on Aug 11, the battery voltage suddenly rises up to 36 V max and the satellite has started resetting in eclipse.
I think the explanation is that the battery experienced a significant event on Aug 11 where it lost the electrolyte in one or more cells. If this is true, the bad news is that it will no longer hold a charge and will not operate in eclipse any more.
But the good news is that without electrolyte, it would also stop dendrite growth that causes the eventual battery short circuit.
In our ground testing, our test battery failed in the usual way with the battery load increasing until the solar panels could not drive the power bus high enough to run the satellite. But interestingly, several cells also cracked and dumped their electrolyte during this testing.
If a cell on the flight battery cracked and dumped its electrolyte BEFORE the shorts were formed, it should stay that way and the satellite may very well continue to operate in the sun until it starts to re-enter. We just need some luck to avoid a bad solar angle that would cause a reset in sunlight