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RE: AO-40 Power Situation



Peter,
Thanks for the info.. Your relay concept has also crossed my mind...
Well if we had a spare 1000# we could do all sorts of things..
Keep up the great work... Lets HOPE..
Regards,
Gunther


-----Original Message-----
From: Peter Guelzow [mailto:peter.guelzow@kourou.de] 
Sent: Sunday, February 01, 2004 3:33 PM
To: Gunther Meisse
Cc: amsat-bb@amsat.org
Subject: 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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