[Elecraft] Solar Power for KX3

[Fred Townsend]

Jim: 
Be careful what you ask for. Solar arrays are not rated for average.
Probably because there is no such thing as an average sun. I'd like to say
they are rated for peak power but that is somewhat illusionary too. How much
power you actually get from an array depends on many things. You will want
to get some sort of charge controller for sure. That is so you can match the
charging requirements of your rig and battery to the array. DO NOT expect
them to be the same without a controller. 
I will offer a little data I collected on a 12x18" array in Southern
California in June. I had a rig and 7AH gel cell in parallel. My peak solar
current was 225ma (.225 x 13.8 = 3.1w) and the rig was drawing right at
200ma in receive. That meant I was pushing 25ma into the battery to replace
what I used on transmit. 
If I could have kept that going I would have been happy. I used the ammeter
to aim the array at the sun. The problem is the sun is always moving. In
twelve minutes my array power was down to less than 1 watt output. That
meant after five minutes I was taking power out of the gel cell to help
power the receiver. If I really wanted to charge the battery I had to turn
the rig off.

Ratings: The manufacturer rated the array at 5 watts but they said it was
the equivalent of a 10 watt array by using their controller.
This was a glass covered array not suitable for back packing. If I were back
packing I would want the more expensive roll-up arrays. Then you need a
frame to hang them in. 
I have never seen any guaranteed ratings on solar arrays. Caveat Emptor. 

73, Fred, AE6QL  

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of jimk8mr at aol.com
Sent: Thursday, April 18, 2013 1:29 PM
To: elecraft at mailman.qth.net
Subject: [Elecraft] Solar Power for KX3

Rather than reinvent the wheel, does anybody have experience or suggestions
for a small solar array sufficient to keep a KX3 with internal batteries
going during daylight? I would assume 10 watts average over a reasonable TX
duty cycle would be enough.? Something strong enough or flexible enough to
withstand packing for air travel would be desirable.


73?? -? Jim?? K8MR

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