Re: Solar Panels (Douglas Todd)

[charles allison-2]

Hi Doug,

My wife has a 50 Watt solar panel she uses for emergency power.  They are
definitely not the transportable or affordable kind - unless you find one
taken out of commercial service and then they tend to be cheaper than buying
new small ones.  She is a net control station and a local ARES member and we
are 30 miles off the water on the lower TX coast.

The panel is used to charge a 12V deep discharge marine battery -
approximately 100 AmpHr.  The panel provides up to about 5 amps.  Even that
scarcely provides enough power for net control activities 2 to 4 hours per
day using the full 100 Watts.

One must scale the system to the radio and to use.  Obviously, you wouldn't
want this setup for a kx1 backpacking  system.  The most common batteries
are called sealed lead acid and provide decent power for size and weight.  A
4 AH or 7AH battery is not too unreasonable for man portable usage and can
generally power a few watts for a reasonable length of time.  In general,
one sees the C/10 term for what the battery is rated at.  A 7AH battery
doesn't mean 7 amps for one hour but rather 7/10 amp per hour for 10 hours
and .350 Amps should last for a good 20 hours.  Also, charging rates tend to
be about this rate also, C/10 although full charge will probably not be
reached in just 10 hours at that rate.

Once the battery is selected for your requirement, then you need to select a
solar panel that can deliver the charging rates needed to charge the
battery, typically in aaround 10 hrs.  Buying new solar panels is not for
most people.  Anything affordable is usually too small for any use other
than to float charge (keeps a battery from discharging).  The surplus stores
offer a significant discount on new pricing for larger panels.  Once the
panel is obtained - one needs a switching regulator for solar panels of that
size.  Some hams offer them and potted commercial ones are also available
for not too much cost as well.  These are needed because the open circuit
voltage could be 20 VDC for a 12.6 volt panel without the regulator.

If you're in ARES RACES emcomm arena, it might be possible to find even the
larger  panels from your local gov. that has replaced them on those solar
powered school crossing lights.


best regards,
Charles Allison
wb5izd (husband of k2/100 and kx1 owner)



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Message: 8
Date: Mon, 3 Jul 2006 10:56:08 -0700
From: "Douglas Todd" <[hidden email]>
Subject: [Elecraft] Solar Panels
To: <[hidden email]>
Message-ID: <000a01c69ec9$f6ebee30$6501a8c0@douglaptop>
Content-Type: text/plain; charset="iso-8859-1"

I'm interested in using solar panels to power the K2 for emergency/field day
operations and am wondering what sort of experience others have had.  The
panels seem expensive: about $100 for a 5 watt panel  but with battery and a
low power draw of the K2, they  look like they can sustain operations for
extended periods of time.

How does this work in practice ? Is there enough 'juice' delivered to keep a
station operational ? How about portability ?

Thanks to everyone in advance for your responses.

Douglas Todd (KE7GYQ)



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[Andrew Moore-4]

As I migrate from QRO to QRP, I am converting my K2 back to a QRP version
(will post KPA100 module as soon as I get pricing data).  As a result, I
have for sale my Astron RS-20M power supply.  It has current and voltage
meters on front.  I bought it new less than a year ago.  Barely a scratch,
works perfectly, USD $95 includes shipping within the U.S.

http://www.photogs.org/out/rs20m.jpg

--Andrew, NV1B


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