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Re: SuitsSat battery life?



Hello John and Everyone,

As we continue to give out "hints" it is refreshing to see everyone's
comments on the construction of SuitSat-1.  Now you can see the challenges
that the SuitSat team had at creating this unique satellite.

To answer your questions, the Kenwood TH-K2 is powered at 12V from a
28V-to-12V DC-DC converter and EMI filter and then the batteries (three 28V
batteries in parallel).  When we integrated the system, we used a bench
power supply to emulate the 28V battery voltage.  As we lowered the voltage,
we found that the radio will stop transmitting at approximately 9V.

You are right that once the batteries reach their "knee" the voltage will
rapidly drop.  If we can, we need to continue receiving as much telemetry as
possible so we can graph the performance of the batteries.  Your guess is as
good as ours as to when or at what voltage.  The fun now is to listen and
graph!

On the question of how long the suit will stay in orbit, that prediction is
3 to 6 weeks.  But with the current elements perhaps someone can do a
calcuation and make a more informed prediction?

- Steve N7HPR




On 2/10/06, John P. Toscano <tosca005@tc.umn.edu> wrote:
>
> I was curious to know how the power is configured to the radio.  If the
> handheld being used is anything like those I own, it requires a battery
> voltage somewhare between 6 and 12 volts, yet the spacesuit batteries
> are providing far more than double that.
>
> Is there a voltage regulator between the batteries and the handheld to
> drop the voltage to what the handheld requires?  If so, at what
> spacesuit battery voltage is the regulator likely to "run out of
> headroom" and stop regulating?  (Depends on the output voltage selected,
> and the regulator design.)  Below that, I suppose that the delivered
> voltage would be approximately equal to the battery voltage, and then
> the question becomes "how low of a battery voltage will still operate
> the handheld?"
>
> I suppose this could all be moot, if the battery voltage drops extremely
> fast once the cells are mostly depleted, and the delivered voltage to
> the radio abruptly goes from "plenty" to "not enough".
>
> But if we continue to accumulate battery voltage telemetry data, it
> would be interesting to plot the falloff rate and estimate how much
> longer SuitSat will likely transmit.  (Oh, yeah, does anyone have an
> estimate of how long until SuitSat starts its final re-entry?  If the
> battery consumption is slow enough, I suppose that could be the
> rate-limiting step in the process!)
>
> 73 de W0JT
> AMSAT Life Member #2292
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