Solar charge controller radio interference

[Sail Rock 28]

Here's a question for the techies out there. I have recently installed a solar panel on my boat with a Tracer 2215BN solar charge controller which works a treat charging the house battery. Only problem is it interferes with the FM radio making it unlistenable (but no interference with AM or VHF). The culprit appears to be electromagnetic interference originating from the charge controller then radiating from the battery cables which pass behind the radio enroute to the switchboard. Passing an FM transistor radio anywhere near the input or output cables to the controller also results in heaps of interference.

 

I'm going to try shielding these cables by either wrapping the existing ones in a stainless steel or copper braid, or replacing them with shielded cables then earth the shields / braid to the boat's RF ground (the lead keel).

 

Has anyone else encountered similar problem and if so do you have any bright ideas? Also anyone know where to buy shielded cables suitable for 12V DC battery loads (marine grade of course)?

Regards

Sail Rock

[Island Time 1,239]

This is a known problem with some charge controllers, esp mppt ones. Try twisting the cables together, and or fitting rf chokes.

I'd also report the issue to the supplier - could be a faulty unit. I've used a few tracers, never had this problem.

[Sail Rock 28]

Thanks IT. I will try these easy solutions first and see what happens.

[wheels 543]

Just like the LED discussion, a choke (Ferrite core) will also be helpful. You wrap the "out" wires several turns through the core of the ferrite. Jaycar sell the things. The interference is of a very high frequency and very high frequencies do not travel well through a ferrite core and get cancelled out. And as IT said, twisting the wires around and around each other can also work. The interference is an RF wave. Twisting the wires mean that the frequency (in basic language) meets itself every turn and cancels itself out.
I expect that wrapping the cables in a shield could be a difficult job, so try the easy way first. Plus shielding RF is a very complex business to make it work, so it may not always work. 

[Sail Rock 28]

Thanks Wheels. Got me some ferrite cores (from Jaycar) and I will give them a go.

[Tim C 23]

I've got a similar problem with rolling lines on my projector image when powered up from 12V. The problem disappears when the projector is powered up by onboard 240 AC power. I've tried twisting feed wires, ferrite cores on everything etc too no avail. Recently had a interference expert aboard, but he couldn't figure it either. 

But I still blame the solar controller. 

First World un solvable problem I guess...

[Island Time 1,239]

Pretty unlikely if it happens at night Tim, but easy enough to disconnect to find out...

The secret is to turn off everything you can to begin with, then add them back one at a time till it comes back. The issue is harder if with everything off, it still happens. Then it's something hard wired. Perhaps, in that case, try a seperate batt for the projector. Could be the internal dc power supply for the projector itself?

 

Nothing is unsolvable!

[wheels 543]

Yes IT is real close with the DC P/S in the projector. It does depend on what you mean by rolling lines, but rolling lines is a common tell tale sign of an AC ripple being found on the DC supply line. It depends on the power supply and what voltage the internals run on. Sometimes the internal circuits may require higher voltages than the 12V being supplied and the PS has a step up circuit which increases the Voltage. Several things can happen that will cause the Rolling lines.
     The 12V battery is getting too low and the PS can not step up the voltage high enough.
     The 12V battery supply does not have large enough wiring for the length of run and the current required and the voltage is dropping in the wiring too much.
      The DC regulator is faulty.
      DC filter capacitors are failing.
It is also possible for another device to be putting a hum on the 12V. Our 12 to 230V inverter has that issue and results in a background noise on the VHF if the inverter is running a high current demand like the freezer. I solved the problem with real heavy battery cables along with the Inverter as close to the bank as possible.
      

[erice 732]

interesting developments in flexi panels

 

50m micro-grid roll up panel in trailer,  deployed by truck in a few minutes

 

http://www.renovagen.com/?services=rollable-pv-array

 

http://www.renovagen.com/?p=623

 

[180S 20]

Wire twisting and controller shielding both hide from the real issue of controller waveform radiation. Better to go back to the supplier and make it their responsibility to come up with a fix. Is not too difficult on a tech bench to suppress spurious radiation.

[Sail Rock 28]

Did you sort the interference Rock and if so how?

 

I want to know if that wire twisting IT mentioned worked. The cunningness and simplicity of that possible fix I find a little exciting

 

............ if that's not too sad a thing to say out loud.

[Sail Rock 28]

Yep. I twisted the wires between the solar controller and house battery and also installed ferrite cores on both the +ve and -ve near the controller. It seemed to do the trick ????

[Island Time 1,239]

ha, not completely useless after all!

[wheels 543]

KM, it works for any interference that is AC and radiates from the wiring itself. By twisting the wiring around itself, you are creating a "winding" or sorts, like in a transformer. Two things then happen to the AC signal radiation. The "winding" is not very efficient at transmitting high frequencies. So that attentuates some of the signal. But mostly, the AC signal tries to induce itself into the other wire, which it "see's" as the other winding just like in a transformer. The other wire does exactly the opposite. But the signal induces itself out of phase to the signal already on the other wire and this the two cancel each other out.
The DC current on the wire is unaffected.
While on that subject, Shielding works a little different again. A cable that is Shielded, means that there is a braided shield around the out side of the other wires inside the cable. The inside wires can be carrying very small signal currents and having "noise" inuced into these can dcause false signals resulting in errors or total loss of function of the instrument. The shield is always connected at one end, usually the main negative/earth connection point. Any outside interference is soaked up into the shield and taken to earth. It only protects the sensitive signals from interference from other wires/equipment.