Having completed the Elecraft K2 with its own built-in battery pack, I am very satisfied  that I can now have a all band HF radio which I can take to field, hook up an antenna, a set of paddles and get on the air in a very short time. No more messing around with power wires and external battery any more! There is a small problem however, the internal battery would last only a few hours. It would not make it through the Field Day weekend. I can bring along a large external battery, but battery's weight would be too heavy to carry around.

Then one day, I saw a sale ad from RadioShack which advertised a small solar panel to trickle charge a car battery for $19.95.  I order one thinking that I could use the solar panel to charge the K2 internal battery or an external 4 Amps/Hr gelcell which I have. When the panel arrived, I quickly put it under the bright sun and measured its output voltage. Hmm, the panel put out over 17V under the bright sun. I wouldn't want to plug this onto my K2 until I can fully investigate if it is safe to charge up gelcell battery that way.

I sent an email to the Elecraft list asking to see if any of over a thousand K2 enthusiasts had attempted to charge their K2 with solar power before and any advise(s) they could give me. Boy, what a responsive group, I got a flurry of emails offering all kind of advises within a very short time! One gentleman was very kindly pointed me to the SunLight Energy Systems Web site to check out their low cost solar charger controller.

As I was browsing around trying to learn more about solar power, I noted that SES had discontinued the older version of the charge controller, the Micro M, and offered to sell the rest of the inventory in kit form for $15.00/kit. That was even better since I love to build anyway.

I called up SES and ordered a Micro M kit. The kit arrived a week later. As stated in the manual, the semi kit has a few parts missing which were not difficult to obtain from a local electronics surplus store. It took only a couple of hours to build and test this little controller including the modification to cut down current drain when sunlight is not available. I elected to build the controller as a stand alone unit instead of installed it inside the K2 as someone from the Elecraft list suggested since I also want to charge up the external gelcell battery.

Since the Battery Saver Plus solar panel can only supplies about 125mA (1.8W), it can only be use to trickle charge / or topping off the 2.9Amp/hr battery of the K2 (Well, it can fully charge the battery after a couple of days) I later purchased a 15W panel which I can use to fully charge the battery is a few hours.

Here are a few pictures of the solar power project which I took during construction:
 

Completed Micro M controller with the current  drain mod
Completed Micro M controller with the current  drain mod (Different View)
The Micro M controller in a homemade box
The Micro M controller in a homemade box (With Label)
The Micro M controller in a homemade box (With Label - Different View)
The Micro M controller (Complete Setup)

I highly recommend the solar power project  to power your field day set up  to anyone who would like to try something different than conventional way of charging your battery. I won't be as cheap as house's electricity, but it is definitely fun. You may be even able to use this set up to charge up your K2 and save a little bit of money (!) during difficult  time such as the energy deficiency  we are experiencing in California right now (grin)

72 es Happy building...

Dan, KE6D