[amsat-bb] Ni-Cd's on Satellites and MASS advantage!

[Jim White]

Another data point.

Falconsat 3 has F size Sanyo NiCads that have survived several instances 
of being pulled down to less than 1V causing a CPU reset during more 
than 12 years on orbit.  Last time I looked at the telemetry the peak 
charged voltage was less than .1V / cell below the original voltage.  
They just keep taking abuse and going, going.

Jim

On 3/14/2020 10:53 AM, Robert Bruninga via AMSAT-BB wrote:
> We have used NiCds on all of my 4 satellites with no battery problems.
>
> They are robust, and survive all student mistakes and require no Battery
> management system when paired with a matching solar panel design.  IE, as
> th batteries approach full charge is the same point where the solar panel
> voltage maxes.  Also NiCd's can be safely overcharged at 10% indefinitely
> with no concern. (you only get an hour in the sun and then 35 minutes
> eclipse)...
>
> Yes, they are twice as heavy as Lithium, but the advantages FAR outweigh
> the criticality of Lithium concerns and complexity of the BMS and total
> failure on overcharge or undercharge.
>
> And MASS is an advantage!   PSAT and BRICSAT-1 are identical 1.5U cubesats
> launched at the same time in May 2015.  But PSAT with big C cell NiCd's was
> made heavier with lead ballast to 2.3kg.  BRICSAT (1.7 kg) with lightweight
> Lithiums has already decayed in November.  PSAT is predicted to last 2 more
> years!  Same thing for identical RAFT and MARSCOM cubesats back in 2006.
> RAFT was ballasted up and lasted TWICE as long as MARSCOM.
>
> For comm satellites, there is no reason to come in under mass.  Always
> ballast up  to the maximum the launcher will allow!
>
> Bob, WB4APR
>
> On Fri, Mar 13, 2020 at 5:58 PM Pedro Converso via AMSAT-BB <
> amsat-bb at amsat.org> wrote:
>
>> LO-19 (aka LUSAT) after 30 years in space is emitting day and night a
>> strong carrier.
>>
>> What is amazing that after over 2 millions charge/discharge cycles its
>> vintage NI-CD batteries are still able to receive and hold charge.
>>
>> It is known that Lithium based batteries usually halve charge capacity
>> after +/- 400 cycles, probably you noticed that on your portable
>> device. https://batteryuniversity.com/_img/content/lithium2.jpg
>>
>> This is just a comment for future satellite plans if long duration is
>> part of the objective.
>>
>> 73, lu7abf, Pedro
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> _______________________________________________
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