FNDC Shunt and sense wires

[JRHill]

I am swapping out the FLAs outside for SimpliPHIs inside and making up cables etc. So I tripped over to the town for some more of the tight, twisted pair that came with the FNDC. Not to found. But I did get a generous amount of 20ga Beldin foil shielded with a bare drain. It is slowly twisted not the tightly FNDC twisted. First is the voltage sense from the PHIs to the FNDC with this wire: What do I do with the drain from the shield? Coil it back and tape it? Best practices, should I connect the drain with negative on one side? Both sides? Is it a non issue? Second is the VFX cut out from the FNDC - again, ignore the drain wire?

Maybe in general I am splitting hairs. Probably. But with the RF interference I still experience how does one deal with the shielding and drain if its available in a cable? I am not an RF guy. But if ya want to wire it right on installation what is the advice? In all these years the RF interference seems to be from the panels and wire leads to the FM, the FM itself and lastly the inverter. But it gets transmitted all over the place. My only hope is to get any AM radio 20' plus away from any conductor. I just don't want to make it worse.

[provo]

I am swapping out the FLAs outside for SimpliPHIs inside and making up cables etc. So I tripped over to the town for some more of the tight, twisted pair that came with the FNDC. Not to found. But I did get a generous amount of 20ga Beldin foil shielded with a bare drain. It is slowly twisted not the tightly FNDC twisted. First is the voltage sense from the PHIs to the FNDC with this wire: What do I do with the drain from the shield? Coil it back and tape it? Best practices, should I connect the drain with negative on one side? Both sides? Is it a non issue? Second is the VFX cut out from the FNDC - again, ignore the drain wire?

Maybe in general I am splitting hairs. Probably. But with the RF interference I still experience how does one deal with the shielding and drain if its available in a cable? I am not an RF guy. But if ya want to wire it right on installation what is the advice? In all these years the RF interference seems to be from the panels and wire leads to the FM, the FM itself and lastly the inverter. But it gets transmitted all over the place. My only hope is to get any AM radio 20' plus away from any conductor. I just don't want to make it worse.

If I understand twpr correctly, you want the current going one way to return in the other half of the twisted pair. So if you're using the drain as the shield, yes, you'd want that drain wire connected at both ends just like the shield wire in a two-wire twisted pair.

As usual, I would hope raysun responds shortly !!

[JRHill]

He's rolling his eyes at my questions.

[raysun]

Ideally a drain wire is grounded at both ends to minimize any antenna effect on the shield. Both ground points need to be at the same potential.

[EA6LE-ONE]

Is there a maximum length and thickness of the FNDC wire that can be used? I thought that you have to use the cables that came with FNDC for correct readout.

[fcwlp]

Both ground points need to be at the same potential.

The important caveat.

[raysun]

Is there a maximum length and thickness of the FNDC wire that can be used? I thought that you have to use the cables that came with FNDC for correct readout.

Several folks have reported using longer sense wires with acceptable results. The voltage and current being carried is very low, so the biggest risk is the longer the wire, the more chance of induced noise.

[sodamo]

When I extended the sensor wires from primary FNDC to secondary FNDC I ran about 10ft of this
https://www.amazon.com/gp/product/B004H ... UTF8&psc=1
Both units stay in sync about 99% of time and will even self correct.

[raysun]

When I extended the sensor wires from primary FNDC to secondary FNDC I ran about 10ft of this
https://www.amazon.com/gp/product/B004H ... UTF8&psc=1
Both units stay in sync about 99% of time and will even self correct.

That looks like good stuff for the job.

If I needed to do this, likely I'd roll off some Cat 6 ethernet cable from the 1000' spool I have.

[JRHill]

Ideally a drain wire is grounded at both ends to minimize any antenna effect on the shield. Both ground points need to be at the same potential.

OK, I need to understand this better in layman's terms. So for the battery sense twisted pair, since the negative is common to the ground bus and single system ground, bonding the negative and the drain at the battery and the FNDC connector is recommended? But regarding the "same potential" part, how is this verified? Literally, since the negative line is connected on both ends the potential would be the same - its just that any RF would be protected by the shield and run off to the system ground? And the unshielded parts of the ground now have any interference. Again, I can shield one line of conductors just to have it emanated through the unshielded parts that are in short proximity. So there is no advantage/gain?

Then there are the shunt leads. The shield can only be tied to the system ground and the shunts are already on the ground line. So there are chances that the shunt line drain using shielded wire could carry current way past their capacity? And the drain can't be tied on the FNDC end....

TY,
JRH

BTW, I'm getting really close to a thousand of the world's most irrelevant, meaningless and stupid posts on this forum?

[raysun]

Ideally a drain wire is grounded at both ends to minimize any antenna effect on the shield. Both ground points need to be at the same potential.

OK, I need to understand this better in layman's terms. So for the battery sense twisted pair, since the negative is common to the ground bus and single system ground, bonding the negative and the drain at the battery and the FNDC connector is recommended? But regarding the "same potential" part, how is this verified? Literally, since the negative line is connected on both ends the potential would be the same - its just that any RF would be protected by the shield and run off to the system ground? And the unshielded parts of the ground now have any interference. Again, I can shield one line of conductors just to have it emanated through the unshielded parts that are in short proximity. So there is no advantage/gain?

Then there are the shunt leads. The shield can only be tied to the system ground and the shunts are already on the ground line. So there are chances that the shunt line drain using shielded wire could carry current way past their capacity? And the drain can't be tied on the FNDC end....

TY,
JRH

BTW, I'm getting really close to a thousand of the world's most irrelevant, meaningless and stupid posts on this forum?

So the wire being run is just the 48V feed from the battery positive and negative bus? If so, that's the least sensitive and highest voltage of all the sense lines (48V v.s. 50mV for the shunts.) Unless you live next to an AM radio station transmitter shack, I don't think impressed RF is going to be much of an issue. Twisted pair is fine (but likely not necessary). Shielded twisted pair is fine (smoke 'em if you got 'em).

The battery negative bus is grounded, yes? Through the GFDI breaker? One end of the drain could be connected there. The other end at, or around, the FNDC.

Its probably unnecessary to ground the shield at all, IMO. Others may have a different O.

[JRHill]

Ideally a drain wire is grounded at both ends to minimize any antenna effect on the shield. Both ground points need to be at the same potential.

And the drain can't be tied on the FNDC end....

TY,
JRH

So the wire being run is just the 48V feed from the battery positive and negative bus? If so, that's the least sensitive and highest voltage of all the sense lines (48V v.s. 50mV for the shunts.) Unless you live next to an AM radio station transmitter shack, I don't think impressed RF is going to be much of an issue. Twisted pair is fine (but likely not necessary). Shielded twisted pair is fine (smoke 'em if you got 'em).

The battery negative bus is grounded, yes? Through the GFDI breaker? One end of the drain could be connected there. The other end at, or around, the FNDC.

Its probably unnecessary to ground the shield at all, IMO. Others may have a different O.
[/quote]

And this is what I was seeking. No, I'm not by any xmitter and actually the opposite. MY RF generation is greater than any incoming AM. I didn't believe any wiring change was going to yield any benefit but I had to ask. But when doing it I'd do it beneficially if possible.

No, I don't wear a tin foil hat.

[EA6LE-ONE]

battery wire from FNDC should be directly connected to the battery terminals. also if you modify the wire length you should find a good Voltage meter to check the voltage at the battery and the value on the FNDC for accuracy.

[JRHill]

Having just rehooked the FNDC yesterday I noticed this AM the Shunt A which I added previously is active with 0.05kWh of continuous draw. Initially I installed the 48:12v converter on this shunt as I was going to bring in a common for all the 12dc stuff to run instead of separate wall warts and was curious about its load. I haven't built it out yet - that's a winter time project. Or maybe I'll find a better use for it in the future. Anyway, its ready to work and is active. BTW, the converter is supposed to be efficient and hopefully draw less than a bunch of warts. Anyway, the fuse to the converter is pulled. But the shunt is registering a 0.05kWh draw. Hmmm. I also noticed that the Battery left side tab is varying constantly for the Inverter and the CC so this is not cumulative but the real time measurement. I never noticed that before.

Seriously, 50 watts off a 250 or 500 amp shunt is ridiculously small but its still one of the reasons for this thread about wire quality, shields and drain lines, routing, etc. I still think that the shunts give the best real time picture of current including of device overhead.

Anyway, I thought to bring this up. 50 watts here and 50 watts there... the next thing is a kWh one way or the other. In Gov't thinking, a billion here and a billion there.... But I won't go there.

[raysun]

If Art Bell was still around, I'd say it was a parasitic draw from a nearby alien UFO base. However, I'm certain there are no whackjobs in the Columbia Gorge area who would support this theory. (Unless of course, you include the obvious UFO base on Mt. Adams.)

Given the coarser, more vitriolic, brand of unfounded conspiracy theories that abound today, the draw is more likely caused by the group one is most likely to vilify.

Get a galvenometer and see if the leakage is flowing in the direction of Portland

Orrrr.... 0.05kWH would be roughly equivalent to 1mAH draw. I do believe that is at the noise 'floor' of the system. It would seem the system is more bounded by engineering limitations than by the limits of one's imagination.

[JRHill]

It would seem the system is more bounded by engineering limitations than by the limits of one's imagination.

OK, this is a done issue.

[raysun]

It would seem the system is more bounded by engineering limitations than by the limits of one's imagination.

OK, this is a done issue.

Ya think? I've got a lot more material, and I'll be here all week!

[JRHill]

Anyway, all the cables are made up. Today I will mill wood for a battery platform. By this afternoon I'll be ready for the truck delivery coming tomorrow. This is a big moment for me/us.

[raysun]

Anyway, all the cables are made up. Today I will mill wood for a battery platform. By this afternoon I'll be ready for the truck delivery coming tomorrow. This is a big moment for me/us.

Hooray!

[sodamo]

Anyway, all the cables are made up. Today I will mill wood for a battery platform. By this afternoon I'll be ready for the truck delivery coming tomorrow. This is a big moment for me/us.

Awesome. Progress, Exciting

[sbrownian]

Having just rehooked the FNDC yesterday I noticed this AM the Shunt A which I added previously is active with 0.05kWh of continuous draw. Initially I installed the 48:12v converter on this shunt as I was going to bring in a common for all the 12dc stuff to run instead of separate wall warts and was curious about its load. I haven't built it out yet - that's a winter time project. Or maybe I'll find a better use for it in the future. Anyway, its ready to work and is active. BTW, the converter is supposed to be efficient and hopefully draw less than a bunch of warts. Anyway, the fuse to the converter is pulled. But the shunt is registering a 0.05kWh draw. Hmmm. I also noticed that the Battery left side tab is varying constantly for the Inverter and the CC so this is not cumulative but the real time measurement. I never noticed that before.

Seriously, 50 watts off a 250 or 500 amp shunt is ridiculously small but its still one of the reasons for this thread about wire quality, shields and drain lines, routing, etc. I still think that the shunts give the best real time picture of current including of device overhead.

Anyway, I thought to bring this up. 50 watts here and 50 watts there... the next thing is a kWh one way or the other. In Gov't thinking, a billion here and a billion there.... But I won't go there.

In poking around the forum, I found a link to calibrating the FNDC individual channels, but it requires a bit of 'surgery' to expose the pots that need to be tweaked, so that might not be a procedure for those that aren't used to working on electronics...

The file is at: https://outbackpower.com/downloads/docu ... p_note.pdf

I would suggest having something like a Fluke 87 or similar to verify with.

[JRHill]

Thank you for posting. And welcome to the forum on your 1st post.

[sbrownian]

Thanks!

I hope to be able to get some answers for a friend that has an older GS8048 system that overshoots voltage and current setpoints, so I'll be putting together a post with some background info and what we're seeing.

BTW, I'm an electronics tech and work both communications, (fiber, radio, telephony, microwave, SCADA and networking,) and do some meter relay / protection stuff for a power generation and distribution company in Washington State, so I have a pretty good background in the theory of how these beasties work. They appear to be very similar to some PWM UPS systems we have, but I'm not really familiar with the idiosyncrasies of the Outback gear!

Steve

[Luminast]

It is interesting that the subject of shielding comes up here, where stray RF so seldom comes up as a topic. Usually we discuss high power DC only. But with power supply sense wires, it is a legitimate concern.

The subject of shielding signal wires is rather complex, and there is some misunderstanding here. A definitive reference of this complex topic is MIL STD 188-124b, which can easily be downloaded from internet search.

The purpose of the twisted pair, and the shield are the same - to prevent nearby RF fields from inducing unwanted currents in the signal wire. Having both shield and twisted signal is not better.

Proper practice is not to GROUND the shield (drain) wire, but to BOND it, at each end, to the enclosure in which it terminates, irrespective of whether the metal enclosure itself is connected to earth ground. In aircraft, for example, controlling stray RF is critical, and there is not earth ground to be had anywhere.

To connect a shield drain wire to the negative terminal of a battery bank, simply because the negative terminals connects to earth ground SOMEWHERE in the system is not good practice.

I could certainly be wrong, but I strongly expect that Outback engineers supply a twisted pair sense wires exactly because the battery bank is often not encased in a metal enclosure.

If it were me, I would forget the shielded wire and follow the choice of Outback engineers by twisting my own pair. To do otherwise is an engineering experiment.

[JRHill]

It is interesting that the subject of shielding comes up here, where stray RF so seldom comes up as a topic. Usually we discuss high power DC only. But with power supply sense wires, it is a legitimate concern.

The subject of shielding signal wires is rather complex, and there is some misunderstanding here. A definitive reference of this complex topic is MIL STD 188-124b, which can easily be downloaded from internet search.

The purpose of the twisted pair, and the shield are the same - to prevent nearby RF fields from inducing unwanted currents in the signal wire. Having both shield and twisted signal is not better.

Proper practice is not to GROUND the shield (drain) wire, but to BOND it, at each end, to the enclosure in which it terminates, irrespective of whether the metal enclosure itself is connected to earth ground. In aircraft, for example, controlling stray RF is critical, and there is not earth ground to be had anywhere.

To connect a shield drain wire to the negative terminal of a battery bank, simply because the negative terminals connects to earth ground SOMEWHERE in the system is not good practice.

I could certainly be wrong, but I strongly expect that Outback engineers supply a twisted pair sense wires exactly because the battery bank is often not encased in a metal enclosure.

If it were me, I would forget the shielded wire and follow the choice of Outback engineers by twisting my own pair. To do otherwise is an engineering experiment.

This subject is close to my heart. Being in a canyon away from most everything the RF I experience is greater than any AM/FM incoming. I won't blame OB directly - it could be the panels and leads down to the components. But if I get away from ANY line, AC or DC, by 20' on either side I can get some bit of signal on the airwaves and listen to a radio - to the degree there is something I want to hear. We know that interference goes everywhere. Even for the night's supper. I've done everything I can in terms of metal conduit, high end twisted and shielded/drain and it doesn't matter or help. Maye it has worked better for those in similar conditions and weak radio signals. I want to know the secret.