DIY Solar Radio

For a long time now I have been wanting to design and install a solar system for my HAM radios. I also wanted solar power to run DC lights inside my workshop, charge AA/AAA batteries and more. I wanted to be able to operate HAM radios and charge basic batteries for handheld operation in the event of a grid failure. I started piecing together parts several months ago, and finally got to the point where everything came together.

The system core is in the batteries. The batteries are sealed gel cells that were originally intended for powering enterprise level servers in the event of power outages. They are in rack-mount form factor, and were wired for 48V operation. Because I wanted a pure 12V system, I redesigned the server packs, and re-wired them accordingly. The end result was 4 banks of 4 12V sealed batteries per shelf, with 3 shelves in parrallel. A total of 48 batteries in parallel with 108 amp hour reserve capacity each.

First I had to re-wire the 48V cabinets to operate at 12V. Doing so required some modification of the 60A fuse spades to accommodate the redesign. I split the eight batteries in to two banks of four. Each protected by its own 60A fuse. The combined cabinets are also protected by a 120A main fuse.

I opted to go with solar panels that could be shipped via standard carrier (UPS/FEDEX) instead of truck freight.  For the size of this system, there was no need to get anything larger.  I definitely wanted high quality mono-crystalline cells and close to 100W output.  I decided on the Astronergy 90W panels found here: http://www.wholesalesolar.com/products.folder/module-folder/Astronergy/CHSM-5409M.html At around $200 each, they are a great deal and well constructed.  Although the panels are assembled in China, they exclusively use raw materials from the United States.

The panels mount to a Iron Ridge side-of-pole mount http://ironridge.com/products/polemounting/overview  The mount is supported by a 3″ rigid conduit, which is secured to a metal structure using strut and clamps.  The whole mount is very sturdy.  I wasn’t really happy with the Iron Ridge default method of mounting to the pole.  They give you 4 hose clamps by default.  Luckily, they include the correct holes to use hard core U-bolts.

The panels came with MC4 connection cables by default.  I purchased a few extensions to make my desired length cables (about 15′).  http://www.wholesalesolar.com/products.folder/cable-folder/mc4-extension-cables.html  You simply snip off the appropriate male or female ends and wire them in to the combiner box.

I decided to go with the MidNite Solar MPPV3 combiner box for joining the two panels together in a protected environment.  http://www.midnitesolar.com/productPhoto.php?product_ID=78&productCatName=PV%20Combiners&productCat_ID=9  They make great quality products, and the combiner box made everything very simple on installation.  Everything was grounded thoroughly with its own ground rod, and tried in to the central RF grounding.

Of course, you need a good charge controller to keep from damaging the battery banks.  I opted for the Morningstar Sunsaver MPPT controller because it was specifically designed to optimize charging on systems of this size.  http://www.morningstarcorp.com/en/sunsavermppt  The quality of construction is excellent with large cooling fins and a convenient remote metering capability.  The unit is programmable for various battery types and other conditions.  They are also a US based company.

The connection from the MPPT controller to the battery banks was accomplished using a Ready-2-Connect 75A break-out http://www.powerwerx.com/powerpole-power-distribution/ps-75-45-4.html  From this connector using 6AWG welding cable, I connected to the battery stack using the standard 120A Anderson connectors.  The APC version of the Anderson’s is not exactly the same as the standard Anderson power poles.  I was able to modify the connector to work by trimming some plastic with a dremel. I also use a Watts-Up meter inline as a backup to the MPPT controller information.  The watts-up gives me a little more detail on charge rate, and input amps. http://www.powerwerx.com/digital-meters/watts-up-meter-dc-inline.html

Overall the system works excellent, and was fairly easy to install.  I accomplished my goal of having a long reserve capacity fully off-grid emergency communications and a power center for charging various 12V devices.  My next project is to design a custom switch panel for the LED lighting, and include some 5V USB charging ports.  I will follow-up with a post regarding those improvements.


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