[amsat-bb] Re: AO-07 healthy CW

Sil - ZL2CIA zl2cia at paradise.net.nz
Tue Nov 28 00:16:13 PST 2006


Thanks. It's a great story and it's rather odd to think that two cells
in that battery were launched into orbit with the rest, but were nothing
more than packing (expensive packing too).

Perhaps the special merit of the "NASA" cells, over those selected by
the "Kayser" process, is that the NASA were designed to go open circuit
after 25 years in space (hi hi). However, while the commonly held view
is that the satellite started working again because the battery became
"open circuit", the telemetry suggests that it is not, so the real cause
may be far more subtle.

There are some very fine wires coming out of the thermally conductive
goo that holds the thermistor to cell no 5. Were these joined to the
yellow and grey wires that disappear under the battery?

I guess there's a special "satellite design" reason that double wires
are used (instead of one thicker one) for the current carrying battery

Leaving aside Geoff's (vk2tfg) point that the telemetry may be
irrelevant because of the doggy value in channel 6D, it would seem that
the five top cells (between half volt point and +12V - numbers 2,3,4,5,6
counting clockwise) are being charged with a current of 80mA and have
reached a terminal voltage of 6.4 volts (8.8 - 2.4). This represents a
voltage of 1.28 per cell (6.4/5) and is thoroughly reasonable. This idea
is supported by the temperature of cell number 5 at 60.28 C.

The five cells between the half voltage point and ground are not so
healthy.  The figure of 2.4 volts suggest that 3 of them are short

Of course anything could be happening. The whole box could be a morass
of goo with leakage currents going everywhere.

I will try and capture some more telemetry myself, as soon as the house
painting is finished and I can remount my satellite antennas..


You made a comment:
"Check channel 6D, anything other than about 0.5 means that the others
are likely to be dodgy (invalid)".

Can you tell me any more about this. How is the value should in channel
6D derived?

Boy, a circuit diagram would be a diagnostic great tool here.

Sil - ZL2CIA

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