Thee is an issue with the cheaper solar controllers - they tend to place the switching transistor in the ground leg, making connections difficult. For example the Sunforce controller that Jim mentions uses an N-channel FET as its pass transistor, in the ground lead. If you then connect the radio or other load to the battery while it is being charged, you can end up with a floating ground. One local solar expert discovered that his setup of this kind caused massive current flow on the shield connection of a USB cable - it was essentially carrying all the ground current!
The better controllers use P-channel FETs in the positive leg of the charger, as shown in Mike Bryce (WB8VGE)’s design in the ARRL publication “Emergency Power For Radio Communications” and also in the CirKits design that Bill mentions. I have a pair of each of these and will be using them this Field Day to keep a pair of Marine deep-cycle batteries charged from a 100 watt solar array and also a 45 watt backup array. I like the WB8VGE design better, but it won’t handle the 100 watt array without modification, which caused me to pick up the CCS3 boards. Unfortunately the WB8VGE kits appear to no longer be available, but the CirKits boards (also designed and sold by a ham, forgot his call) are very much available and a fun build. - Jack, W6FB P.S. Listen for both Bill, myself and many others from the WVARA operation at Mora Hill, CA using the call K6EI in FD. It is an all-K3/QRP operation with outstanding antennas in a location you have to see to believe. And, if you are in the area and searching for a place to play, look us up! > On Jun 8, 2016, at 10:36 AM, Jim Brown <[email protected]> wrote: > > 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. > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
