[Elecraft] Field Day

[Bill Frantz]

I have been using a solar charge controller from CIrKits 
<http://www.cirkits.com/scc3/>. The kit comes in a 20A version 
and there are modification instructions for 40A, 60A, and 80A. I 
have the 20A version and have noticed no RFI in my suburban QTH. 
The higher current modifications change some of the circuit 
resistors to keep the RFI low, so low RFI was one of the design goals.

This controller feeds full panel current to the battery until 
the voltage reaches the float voltage and then floats the 
battery at that voltage. This techniqueis a good for lead-acid 
batteries but is probably not appropriate for lithium family chemistries.

It is also not the most efficient way to charge a lead-acid 
battery. Higher efficiency can be achieved by charging at a 
slightly higher voltage and only reducing the voltage to the 
float voltage when the charge current becomes low. With my 7.5A 
rated panels, I can recover the batteries charge in a day after 
spending a weekend contesting at 100W, so the additional 
efficiency is not a major concern. The charge system also works 
well on field day at QRP power levels.

73 Bill AE6JV

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Bill Frantz        | Ham radio contesting is a    | Periwinkle
(408)356-8506      | contact sport.               | 16345 
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