[Elecraft] Solar Panels on sale !!

[John R. Lonigro]

If you have the 5 Watt solar panel in parallel with a 7 Ahr gelcell and 
with a K2 that is turned on, you should not have to worry about 
overcharging the battery, at least not after your first QSO or two.  
After the first QSO, the battery will no longer be fully charged and you 
would be in no danger of overcharging it with the current the panel 
produces.  Just make 2 or 3 QSOs before attaching the solar panel to the 
battery and your worries will be over.

Remember that 5 Watts is pretty much the absolute maximum output of the 
panel.  An overcast day or an imperfectly aimed panel will bring the 
power down quickly.  If the panel is putting out 3.5 Watts or less, it 
won't be putting any charge into the battery.  Everything will go toward 
running the radio.  The maximum of 5 Watts produces about 360 ma: 250 
would go to the K2 and 110 would go to the now slightly discharged 
battery.  A 7 Ahr gelcell can handle about a 1 Amp charging rate without 
damage.  As Field Day progresses, your battery will slowly discharge, 
not overcharge, unless you don't transmit at all.  By late afternoon, 
with the sun at a lower angle, you'll be lucky to get 250 ma out of the 
panel, at which point you won't be charging the battery even during receive.

Remember to disconnect the solar panel once the sun sets, unless you 
have a blocking diode in series with it.  Otherwise, once the panel 
voltage gets below battery voltage, it acts as a load and will drain 
your battery.  You can hook it up again Sunday morning, at sunup.

John AA0VE

Sandy W5TVW wrote:

>I'd watch the voltage on the gel cell batteries!  They can be "floated" at  13.4-13.6
>volts continuously or 1.47 volts for about a day.  Much over this and the life goes
>to hell.
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