Charge controllers and RFI, EMI etc.

[sdold]

We've been fooling around at work with different brands of charge controllers hoping to find something that is "quiet" enough to use at radio sites. We recently bought an Outback Flexmax 80 and a Morningstar Tristar 60A and compared them, both running at about 55A. We looked at the VHF lowband (6 meters to hams) and highband (2 meters) spectrum since that's what we mainly use and where we usually get RFI. I was surprised at te difference and thought other hams might be interested. Usually we use simple on/off controllers for RF quiet-ness, but I've been wanting to try MPPT. Here are some spectrum analyzer plots taken from dipole antennas about 25 feet above the working system.

Anyway I thought others might be interested, and if you have ideas for other brands I should try, I'm all ears.


solar test 1.jpgOutback_HB_812W_30ftVert_10ftHorz.GIFOutback_LB_40-41MHz_Zoomed.GIFTristar_LB_775W_30ftVert_10ftHorz.GIFTristart_HB_775W_30ftVert_10ftHorz.GIFOutback_LB_741W_30ftVert_10ftHorz.GIF

[bob-n]

That is really interesting. Thank you for the work and sharing the results.

Just below 2 meters is the FM broadcast band. Any chance of repeating the measurements there?

[sdold]

Thanks Bob, not on another field trip, but I'll make sure we take a look in the lab, where we're going to do 450, 700/800 MHz measurements.

[bcroe]

Your on-off controllers make make less noise, but it will be hard to control since
the changing current is in all the wiring. If you use good filtering and shielding on
an MPPT controller, you will just have quiet DC flowing away from it. Bruce Roe

[Sunking]

Steve I have done quite a bit of testing on Charge Controllers. Like you discovered they are extremely noisy. Ham radio operators as a whole do not know a lot about electrical power or how to resolve noise issues. Example they will spend countless hours and a lot of money trying to eliminate noise on the DC Output.

Problem with that is it is the Panel INPUT causing the problems, not the output. As you know the Controller has a MOSFET that Opens and Closes around 8 to 16 Khz. That causing a lot of Ringing on the Panel Wiring and radiates. Input needs the Common Mode Filters, not the Output.

OK there is one manufacture that makes quite controllers but of no use to most because they are too small. Genasun makes Controllers for the Marine Market to be used on NAV/COM equipment. Some Hams could easily use them for rigs operating on 12 volts with 100 Watt TX. 15 amp controller is about the right size you can use for a pair of smaller golf cart batteries.

I had solar set up in my shack in Panama, but gave up on it because it still sucks. I know hams spout off it is about emergency communications which ham radio no longer plays a part in. Cell phones did away with ham radio. If they only knew their DC Power Supply that they have is a Floating Battery Charger with ZERO NOISE issues, and the batteries are there in the event of power failure and sized to run for days. That is how the pros operate.

Now then I do have about 100 off-grid Micro-Cell Sites under my belt still in operation. Don't have those RFI issues. All wiring is in metal raceways, and panel input is filtered. At 800 Mhz and up is not much of a problem like the lower frequencies.

Off-Grid Solar is not much of an issue. It is the darn Grid Tied Systems that have wiped out radio. Try traveling Hwy 1 up and down the Calaphonie Coast trying to listen to AM. Not going to happen, way too much RFI directly linked to Grid Tied Inverters

[bcroe]

Put a tight hardware cloth shield around your converter/inverter, filter every lead leaving
the cage as required to get results. Filters at those power levels can be expensive, but
cheap ones can be built from the junk box. This does not work when the micro inverters
are scattered among the array, with all that wiring becoming a noise antenna.

First thing I checked when My Fronius came on line, was the noise. It was very low, and I
could see a good commercial quality filter mounted inside. Bruce Roe K9MQG since 1958