MPPT charge controllers and potential RFI

Mark40930 · August 2013

Good evening everyone. I have been lurking for awhile and have browsed through many of the forums and have picked up some good info.

However, I need some guidance from any of the ham operators who are on the forum for this issue that my searches have not come across yet:

I plan on putting together an off-grid 12VDC system to run a remote shack on some property near Kingman. I plan on piecing together the components I need as my budget allows. My primary concern is with the MPPT charge controller and potential RFI issues which may affect my usage of the shack. Are there any particular models which would be better to use which would minimize interference to my radios, assuming proper install and grounding were followed? I have been looking at either the Midnite Solar Classic 150 or the Outback FLEXMax 80 models as the best selection for what I plan on putting together.

I look forward to any info and/or additional questions that you all would offer. Thanks in advance!

(Update: Just happen to notice the RFI note regarding the Outback controllers right after I posted, any issues with the Classic?)

waynefromnscanada · August 2013

Re: MPPT charge controllers and potential RFI

Being with our local Volunteer Fire Dept, I wear a pager at all times. This pager operates in or very near the 2 meter band (151.745) and whenever my Outback MX-60 is charging even a couple of amps, it sets the pager crazy if I'm within 10 or 15 feet of it, Even through the sheet steel siding on the building that houses the controller. It only causes the RFI while it's actually charging. The Morningstar TS-MPPT-60, located 2 feet away from the MX however, does not, or at least has not bothered the pager at all.

niel · August 2013

Re: MPPT charge controllers and potential RFI

welcome to the forum.
for the most part you should be fine, but there may be a few birdies encountered. using good practice for wiring and rfi measures will help from the get go. also note that the more power being fed through a cc will tend to generate more rfi too. good grounding, shielding, and separation between antennas and radio equipment from the solar wiring and solar equipment also helps.

icarus · August 2013

Re: MPPT charge controllers and potential RFI

My rogue kills very weak (over 100 miles away) FM broadcast band signals, especially down low on the band. Strong signals are fine.

Tony

niel · August 2013

Re: MPPT charge controllers and potential RFI

yes, the background hash from some ccs can show up to wipe out very weak signals, but it still can be improved upon in many cases with the right know-how. this will vary by controller too as my classic currently is below my noise floor. my power production is not high either, but i will also get a good indication once i figure out how i'm going to mount some more pvs. i sense i'll have a bit of rfi to challenge me, but it won't wipe out everything for me and certainly i won't see much in the vhf and higher bands if at all.

Mark40930 · August 2013

Re: MPPT charge controllers and potential RFI

Thanks for the info everyone. I am leaning towards the Classic since it has on-board Ethernet capability and that will help with remote monitoring of the PV system.

I plan on using RFI chokes on the power output from the controller to the batteries (2 x Crown 6CRP400) and on the outputs from the batteries to the loads, and likely from the PV input from the combiner. Combined with proper grounding I think this will help minimize noise from the power system.

Meanwhile I will keep lurking and learning...:cool:

NorthGuy · August 2013

Re: MPPT charge controllers and potential RFI

Mark40930 wrote: »

I plan on using RFI chokes on the power output from the controller

Most MPPT controllers already have a choke on the output.

lorelec · August 2013

Re: MPPT charge controllers and potential RFI

Mark40930 wrote: »

I plan on using RFI chokes on the power output from the controller to the batteries (2 x Crown 6CRP400) and on the outputs from the batteries to the loads, and likely from the PV input from the combiner.

If RFI turns out to be a problem in your system, it's probably being conducted out of the PV wires from the controller. I would concentrate my efforts there first, and place any filtering devices as close as possible to (or inside of, if space permits) the controller. Once it gets out it can be very difficult to attenuate.

Marc

BB. · August 2013

Re: MPPT charge controllers and potential RFI

Also, if you can used metal conduit for at least the first 10' (at least for frequencies over ~30 Mhz to ~180 MHz range) that will help. The conduit needs to be electrically connected to the source of the radiation (metal case of charge controller). The metal conduit (or woven metal sleeve) will capacitively filter out much of the common mode emissions from any cables leaving the charge controller.

Don't parallel run your PV input and Battery Output close together. If they need to cross, do it at right angles (if not in metal conduit).

If your frequencies of interest are below 30 MHz--that is a tough one to address. Generally, the emmissions are best addressed by mounting the MPPT/Off Grid Power System and the antenna(s) as far apart as possible. You can also try conducted noise filters on the power lines--But DC filters are usually much larger and more expensive vs AC filters of the same current rating (saturation of ferrite by DC current).

-Bill

Vic · August 2013

Re: MPPT charge controllers and potential RFI

Hi Mark,

Welcome to the Forum.

First, there are 13 pages RE RFI here:

http://forum.solar-electric.com/showthread.php?5887-Radio-Noise-from-PV-System

And as has been noted in this Thread, separation of antennas from PV array and the power electronics works well, generally.

The frequencies of interest to you also matter. We use shielding -- all above ground conductors are in tight metal pipe. Common-Mode chokes on the PV inputs to the CC and on the outputs as well work fairly well.

The Classic is a great CC, and we use them here on our remote off-grid Hammie QTHes with great success. The Classic, among some other CCs are FCC Class B rated.

And the filtering that is installed in CCs is often there to meet Class B or IEC Emissions Standards. FCC B is a fairly high degree of emission, and for CCs, this test begins at 30 Mhz, and completely ignores the HF and AM BC freq ranges. The filtering installed in CCs might well just barely meet the test limits. Filter components can be expensive, so there is an incentive to not go overboard on emission reduction. So, adding additional filtering and perhaps different kinds of filters can help a lot

The lower bands -- 160 and 80/75 Meters are usually the bands most affected by CC emissions. These bands are most useful for DXing near Grey-Line when the CC can still be producing some power. The Buck Converter is the most noisy part of almost any MPPT CC. If you can separate these antennas from the PV array and its wiring this helps. Also believe that Vertical antennas should be less affected, at least that is what is noted here.

In the past, did have a 160 M Dipole antenna running within about 25 feet (broadside) to the PVs, and with the noted measures that have been taken the interference from an OB MX-60 CC was not very intrusive at all, when measured during the day when the band is closed but the CC running. Noted NO birdies or any noise at night when the CC was sleeping, but still had control/display electronics running.

That is the quick read from this off-grid location, chosen to be as far away from Power Lines and near-by neighbors as practicable.

As a side note, Inverters can generate a considerable amount of RFI. And Inverters sold in the US, generally attempt to meet FCC B. And in this case there are measurement of Radiated and Line Conducted Emissions from below the Broadcast band into the Ghz range. Still, even compliant Inverters can really Hash things up. Common Mode chokes, separation and shielding (underground power feeds are essentially adequately shielded if 24" below grade in PVC in my experience) all work fine for Inverter RFI as well. Choosing an Emission compliant Inverter will help, and should be a requirement in your consideration ... but additional measures help a lot more than just basic FCC B or IEC alone.

It is very good that you are paying attention to these matters before you dive into making your own power.

Opinions. 73, GL, Vic

BB. · August 2013

Re: MPPT charge controllers and potential RFI

As Vic says--Watch for FCC Class B (or Class A for commercial).

A lot of off grid power manufacturers think that FCC A/B does not apply to them--And many times it shows (lots of hash everywhere on the spectrum).

If you limit yourself to Class B (or even A+B) for inverters+charge controllers--You will be starting off with better hardware designs.

-Bill

Scuba-Junky · September 2013

Re: MPPT charge controllers and potential RFI

I'm in the same boat. I just don't want to buy a CC and find out it is a noise generator. I've read a while ago about someone had a cc and tried everything, filters, chokes, metal conduit, extensive grounding etc, and was UNABLE to clean up the RFI. I just don't want to invest a bunch of $$ and end up with something that is unusable. I've been looking at the Morningstar TS-MPPT-60 which is FCC Type B certified. That certification is only for frequencies above 30 Mhz which doesn't help much. What we need is some ham operators who actually are using a MPPT cc to respond with make model and specifics regarding their setup and results.

Have you purchased your cc yet? Success?

Vic · September 2013

Re: MPPT charge controllers and potential RFI

SJ,

ANY MPPT CC generates noise. PWM CCs do as well, but at a much lower level of RFI energy.

It is really up to the person designing and implementing the power system to reduce/eliminate THE RFI that is generated. Often it is not necessary to completely eliminate it, just to reduce it to an acceptable level.

The neat thing it that YOU are in control of most of any of the emissions generated. Vic

waynefromnscanada · September 2013

Re: MPPT charge controllers and potential RFI

Interesting note on the MX-60, it sets my fire dept pager crazy but only while actually charging. And it makes little difference if it's charging @ 3 amps, or 60 amps. It also nails the pager through galvanized steel siding on my solar shed.
On the other hand, the Morningstar TS-MPPT-60 doesn't bother it at all, not one little bit, no matter how heavily it's working.

Vic · September 2013

Re: MPPT charge controllers and potential RFI

Hi wayne ..,

I do not know just what the emissions from the MX-60 are, but know that it has not been noted as being compliant, and doubt that it is.

The Classic IS FCC Class B. Using Common Mode chokes on all power conductors, and keeping those conductors in tight metal pipe probably helps a lot. Also, both power rooms here are in tight Cargo Containers, which cannot hurt.

It would be nice if someone (else) would do apples-to-apples RFI testing on CCs. Would be nice to know how they do stack up. Vic

PNjunction · September 2013

Re: MPPT charge controllers and potential RFI

Mark40930 wrote: »

I plan on putting together an off-grid 12VDC system to run a remote shack on some property near Kingman. I plan on piecing together the components I need as my budget allows.

Hi Mark - that's the most expensive way to do it. What kind of remote shack are we talking about - repeater system, casual HF remote, or hard-core DX remote? Knowing the power needs up front will help you from following the constant-upgrade ($) trail.

MPPT is great, but I just want to make sure you aren't over-doing it, when a much less noisy pwm might suffice for a low-power barefoot shack that is running 12v gear with short cable runs - especially due to your location and generally good solar-insolation.

Vic · September 2013

Re: MPPT charge controllers and potential RFI

PNJunction,

Good point about aiming low if possible and generally PWM CCs have much lower emission levels.

However, for those wanting it all, MPPT CCs can be tamed. And if there is some situation where an MPPT CC causes undesirable levels of RFI, it can be shut off for some time while the radio activity is occurring, especially if on has reasonable battery capacity, and RE charge resources.

AND, for DXers, quite often the best DXing happens around Sunrise and Sunset, when there is usually very little charging going on anyway.

Opinions, Vic

Mark40930 · September 2013

Re: MPPT charge controllers and potential RFI

PN,
The shack I am putting together will be for casual HF operation on the weekends. I bought the land to use as a weekend retreat and I figured it would be a great place to set my gear up without having to worry about pesky neighbors.
Since it would cost about $60,000 to run a power line out there (per Unisource, the local utility), off-grid is the most reasonable option.
The main focus would be on HF, although I will have some VHF/UHF capability as well, and I have tentatively decided on using a setup similar to what NASW is offering here:
http://www.solar-electric.com/rvmakitwi630.html
Since I'll have the 100W HF rig, a 50w dual-band mobile, 25W GMRS base unit, the auto-tuner, a laptop, and some lights, I wanted the capability to ensure I have enough power and the recharging capability to make sure I don't run batteries down below 75% SoC (but I'll save details about that for another posting when the time is right up so we don't go off topic).
I do plan on ensuring proper separation between the RF cables and my power leads from the batteries, as well as having my HF vertical about 40-50' away from the shack; this combined with the precautions of using toroid chokes on the power cables from the charge controller to the batteries and from the batteries to my loads should keep RFI to a tolerable level.
In reply to Scuba-Junky, I have not yet purchased any of the equipment yet as the site is still not yet prepped yet as first thing on the agenda is finish grading a road about 100 yards and across a wash to get to the property, then clearing the site.

MPPT charge controllers and potential RFI

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