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Re: AO-40 Power Situation



Hi Gunther,

what you suggest would only work if we keep the AUX battery fully charged.
This however might even shorten it's lifetime. The AUX battery was
supposed to be kept not charged until it is needed..

In addition you would need to add 4 of these high power diodes and
loose a lot of power and dissipate a lot of heat.  Additional relays
will be needed..

The problem is, that the battery cells failed too fast in something
like a domino effect. That kind of behavior was not expected and
could not have been foreseen.

I have some other ideas in mind, but not sure if that might not be
a problem in a different scenario..  For example, you could use
a normal relay which is simply powered from the Bus and disconnects
the battery when the Bus voltage drops under a certain extreme low level,
which normally never occurs.. even under high load.
The BCR can run without battery, thus the satellite would work when
not in eclipse. This would give us enough time to charge and switch
over to the AUX battery..
But again, such a behavior we have experienced now, was not expected
and thus the battery switching was not designed for this kind of
failure scenario..

73s Peter



Gunther Meisse wrote:

> Peter,
> The discussion about the problem on AO-40 brings to mind the question:
> Why would we not place 50~70 Amp steering diodes in series with the Main
> & Aux battery sets, after the charging circuits, to prevent either from
> dragging down the other battery or the power bus? Other than more weight
> and another component to fail, is there some good space science that
> says no?
> Regards,
> Gunther Meisse
> W8GSM
> AMSAT LM:594
> 
> 

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