Note of caution:
Normal silicon solar cells (panels) CANNOT be connected directly to a battery
without diode isolation, preferably a schottky diode for lower voltage drop. In
darkness they will suck the life out of the battery. Some panels really do have a
diode built into the panel itself but don't anticipate it. Even though the output
of small panels won't necessarily "cook" the battery, some sort of regulation
should be designed into the circuit as just plain good engineering. Panels just
don't stop charging by themselves.
Rick

"M. Adam Davis" wrote:

> Since this sounds like a one-off, might I suggest a quick and dirty
> (possibly cheaper) solution?
>
> You can get solar powered landscape lights which come with a solar cell,
> some charging circuitry, two NiMH batteries and an LED for under $20
> (sometimes for half as much).  Some are set up with a CDS cell to only
> operate at night, others operate the LED when the batteries are
> providing more voltage than the cells (ie, it must be dark), so some
> modification will be necessary.
>
> But IIRC, the solar cells were set up connected directly to the battery
> and circuitry.  They are essentially diodes, so they don't discharge the
> battery (even at night), and charging (and overcharging) is based on
> current, which the small solar cells cannot provide too much of even in
> full sunlight.  The solar cells only provide up to a certian voltage,
> and the batteries stop charging once their voltage increases beyond what
> the solar cells can provide.
>
> Hope this gives you some ideas...
>
> -Adam
>
> marco genovesi wrote:
>
> >Hi all,
> >I'm thinking to an "essential" solar-charging system for a prototype of a
> >"very remote" meteo-station . Average current consumption of the logger with
> >all sensors is little, about  100-150 uA, so a possible solution can be a
> >very little solar cell recharging a pack of 3 or 4 NI-CD cells (AA type). I
> >have tested with a small  (1" x 3") solar cell from a toy and I have
> >measured about 40 milliamp. out in direct sunlight. I'm not an electronics
> >expert but I suspect that this current is too high when the cells are full
> >charged and a regulator will be mandatory (or I'm wrong?).
> >I have read on PICList a lot of e-mails about a solar-charging system some
> >days ago, but it seems a bit excessive for my use.
> >Can anyone suggest me a simple and rugged solution for regulator?
> >
> >thanks in advance
> >Marco
> >
> >--
> >http://www.piclist.com hint: The PICList is archived three different
> >ways.  See http://www.piclist.com/#archives for details.
> >
> >
> >
> >
> >
>
> --
> http://www.piclist.com hint: The PICList is archived three different
> ways.  See http://www.piclist.com/#archives for details.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.