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

[Robert Bruninga]

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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