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
Completed Micro M controller with the current drain mod
72 es Happy building...
Last Update: May 02, 2001 at 1600 PDT