[aprssig] Solar charging again

scott at opentrac.org scott at opentrac.org
Thu May 5 23:07:35 EDT 2005

I hadn't realized the trickle rate was so high on the AAs.  So what should
my target open circuit voltage be on the panel, relative to the battery


-----Original Message-----
From: Robert Bruninga [mailto:bruninga at usna.edu]
Sent: Thursday, May 05, 2005 5:14 PM
To: aprssig at lists.tapr.org; scott at opentrac.org
Subject: Re: [aprssig] Solar charging again

>>> scott at opentrac.org 5/5/2005 6:18:46 PM >>>
> I'm interested in solar charging for small systems...
> The average power... can be kept to under 50 mW.
> The tracker maybe 6 mA at 5 volts...  I figure a
>6" by 6" or smaller panel should be able to do it
> but I'm not sure about the efficiency of small
>charging circuits.

You dont need any circuit.  Just hook the panel to the
battery through an isolation diode.  Reason is, you
want every bit of current into charging and you cannot
possibly overcharge the battery with such a tiny panel.
(assuming you are Using AA cells)...  Also use NiCd's
instead on NIMH since they are less critical to
chargning anomolies...

For AA nicads, the trickle charge rate is probably 50
to 100 mA for 500 or 1000 MAH cells.  So as long
as your solar panel cannot pput out more than
50 or 100 mA, then there is never any problem with


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