[Elecraft] Solar Charge Controllers (was Field Day)

[Jim Brown]

Yes on all counts. This unit would be described as a simple hysteresis 
controller -- it doesn't pulse the charge current, it simply turns 
charging on if the battery voltage is less than full charge, turns 
charging off when that voltage is reached, and turns charging back on 
when battery voltage has dropped some pre-set amount. Chargers like this 
are, by their nature, free of RFI, because there's no square wave to 
generate RF trash. Several years ago, a local ham pointed me to this 
product, which does the same thing, but is rated for a lot less current.

https://www.amazon.com/Sunforce-7-Amp-Charge-Controller/dp/B0006JO0XI/ref=sr_1_1?srs=2601531011&ie=UTF8&qid=1465406526&sr=8-1&keywords=solar+charge+controller

The more efficient charge controllers of which Bill speaks are MPPT 
controllers; they have a DC-DC converter that converts the relatively 
high panel voltage at low current to lower voltage at the higher current 
that the battery can accept. This allows a large battery to accept more 
charge in a shorter period of time. By their nature, they use square 
waves, so they can be noisy, and most MPPT charge controllers ARE noisy. 
The Genesun MPPT controllers create very little RF noise, and won't be 
heard in most installations. My solar panels are next to my 160M 
antenna, so I need a choke on panel side of the controller to prevent 
noise pickup on that antenna. That's a pretty extreme condition. :) So 
I'd call the Genasun controllers RF quiet.

73, Jim K9YC

  On Tue,6/7/2016 6:12 PM, Bill Frantz wrote:
> 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.