Resolution

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Resolution

Postby JRHill on Sun Sep 20, 2015 6:06 pm

Flexnet DC needs shunt options for lower amperage draw ins and outs. Upgrading from a Mate to a Mate3 and adding a Flexnet DC hasn't seemed to gain me anything except another programmable signal output.

A 250 amp shunt? Really? A tree falling in the forest or my cell ringing probably causes more variance in resolution on a 0 to 250 amp shunt/leads. Bigger loads in and out seem fine but small loads over night/time are important as they accumulate especially during winter hours when on generator power. The way things are, these small loads would seem to fall into tolerances and aren't even measured with any accuracy. A 125 amp shunt would be better. How about a 80 amp shunt?

Best regards,
Jim
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My RE system: -House: FM 80, VFX 3648, FlexnetDC, FlexWare xformer, Mate 3 / Hub, WattPlot/, 2925w SunTech 195, Trojan L16RE-B Batteries. Backup 1: Champion 75531i 3100, backup 2: 11kw Miller Bobcat;
-Well: Grundfos 11-SQF-2 pump, controller & AC switch (CU200, IO101), Morningstar 15a/48vdc Controller, 780w SunTech 195, Trojan golf cart batteries.
-All running since July '11 with no critical problems.

Re: Resolution

Postby larrywa on Tue Sep 22, 2015 4:42 am

Yeah but it is one-size-fits-all. Think about the loons that try to run a household on a 12v battery bank.

250 amperes is only 3000 watts and my guess is that the voltage is really only about 11 volts at the inverter after lead and connection losses, Peukert factor and all the other "what happened?" factors.

Maybe it's time OB started corralling inverters into voltage ranges. like 12v units only peak at 1200 VA and the FD-DC comes with 250A shunts, whereas the 48v inverters come as 3600 VA (it was never watts) and the FN-DC comes with 80 ampere shunts.

The OpticsRE truncation of power readings is the one I like the best. The poor bastard running 200 watts on two CC units will never register more than 0
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Posts: 351
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My RE system: FlexPower Two
2 x GVFX3648s,
2 x FM80s,
FNDC w/3 shunts,
Mate3 v3.015.005 (works excellent!)
Hub 10.3,
PV:1000W east@45, 600W west@45, 2400W south@19 deg.
Battery:48v @ 130Ahr Crown batteries, deep cycle <$380 for 6.25kWh

ISY994i HA, Insteon, X10, Philips Hue, MiLight bulbs & RGBW strips
WebControl 8 as weather station stuffing
ISY994 variables via REST interface

Raspberry Pi3 x 2, Pi1 B+

Re: Resolution

Postby klundquist on Tue Sep 22, 2015 8:17 am

Jim,

Shunts have two ratings. The standard OutBack shunt is 500A/50mV. The 500A rating indicates how much current it can handle and still read with some accuracy. Shunts typically like to operate at 70-80% duty cycle or less so the 500A shunt is really rated for <400A of continuous current. The second rating on the OutBack shunt is 50mV. The shunt is a resistor so the 500A/50mV rating means that at 500 amps of current the shunt provides 50 millivolts of resistance. When one amp passes through the shunt there is a .0001 volt drop. If the voltage on one side of the shunt was 24V, the other side of the shunt would see 23.999V. The little wires from the FN-DC that attach to the side of the shunt sense the difference and translate it into current flow. The 500A/50mV shunt has a 10000:1 ratio and I would say it is a pretty good balance between accuracy vs. resistance.

By the way, if you have an accurate digital volt meter that can read millivolts you can put the probes on each side of the shunt to measure the amperage flow via your voltage reading. Since 10mV = 50A if you see 10mV you know there are 50 amps passing through the shunt. If you see 1mV that means the current flow is 5A.

Here is a little light reading for more info on Shunts http://spectrumindustriesinc.stage.thom ... -Info-.pdf

-Kurt
Kurt Lundquist
Alpha Energy Systems Engineer
http://www.alpha.com/solar
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Re: Resolution

Postby JRHill on Tue Sep 22, 2015 9:03 am

Thanks Kurt,

I understand the theory but in reality things are different. For example, right now: I can hear the deep freeze running. In addition is my LED desk lamp, laptop, 2nd monitor, router, satellite modem, sat TV receiver and flatscreen (both idle), refrigerator (idle), beverage fridge (idle) and a few misc wall warts. The system shows .1kW of load as it has each hour all night long with the exception of 1 and 4am when the load was zero. I know that if I take my Fluke and the DC clamp-on out to the battery box I will see 5 to 6 amps of draw while the Mate3 shows .1kW. If I turn on the hot plate, the load will jump to .6-.7kW and the actual will be ~ 17amps. This is the way things have always been and I had expected that the addition of the FlexNet with the shunts would move me much closer to seeing the real loads, including the overhead of the inverter. The result is that things haven't changed in the least.

Smaller shunt options should increase the sensitivity many times over esp. for light, constant loads which are of import over a 24 hour period.

Don't get me wrong as I'm not being critical. While I have read that there are some off grid folks who have resistance heated saunas and hot water heaters ( :-0 ), a few hundred watts is a drop in the bucket. But I would venture that there are a lot more systems being used more conservatively and those smaller loads are unaccounted for as things are. The pieces are in place for better measurement, they just don't accomplish it.

Best,
Jim
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Posts: 336
Joined: Thu Feb 17, 2011 12:12 pm
Location: South central WA
My RE system: -House: FM 80, VFX 3648, FlexnetDC, FlexWare xformer, Mate 3 / Hub, WattPlot/, 2925w SunTech 195, Trojan L16RE-B Batteries. Backup 1: Champion 75531i 3100, backup 2: 11kw Miller Bobcat;
-Well: Grundfos 11-SQF-2 pump, controller & AC switch (CU200, IO101), Morningstar 15a/48vdc Controller, 780w SunTech 195, Trojan golf cart batteries.
-All running since July '11 with no critical problems.

Re: Resolution

Postby JRHill on Tue Sep 22, 2015 7:36 pm

I am old enough to admit a screw up and to take the heat. Forgive me OutBack folks and others.

After the third day of watching the Mate3 with the FlexNet it was obvious the readings were exactly the inverse of what they should show. I verified that I wired the shunt leads to the correct device but the Device and Batt- leads were reversed. You can imagine how crazy and confusing the readings were. I deleted the data and started fresh. In the time since (6 hours) the ins and outs to the Flexnet look really good. Still the load on the inverter is way to course but I know how to take that - it's not so important - other things are doing their job.

Please reduce my posting status to Outback A$$. I hope someone else may gain from my experiences.

One other time I thought I had made a mistake but I was wrong.

Best,
Jim
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JRHill
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Posts: 336
Joined: Thu Feb 17, 2011 12:12 pm
Location: South central WA
My RE system: -House: FM 80, VFX 3648, FlexnetDC, FlexWare xformer, Mate 3 / Hub, WattPlot/, 2925w SunTech 195, Trojan L16RE-B Batteries. Backup 1: Champion 75531i 3100, backup 2: 11kw Miller Bobcat;
-Well: Grundfos 11-SQF-2 pump, controller & AC switch (CU200, IO101), Morningstar 15a/48vdc Controller, 780w SunTech 195, Trojan golf cart batteries.
-All running since July '11 with no critical problems.

Re: Resolution

Postby larrywa on Fri Sep 25, 2015 5:31 pm

While the confessional is open...

I used a Midnite Solar combiner box with two FM80s. I split the combiner supply bus bar into two pieces and hooked it up. My two shunt currents never made any sense but the total always worked out to correct metering according to clamp on readings and the FM80 readouts.

One day, after this really pissing me off for a few months I started making some scratch schematics and it suddenly dawned on me that the FN-DC shunts were in the negative circuit and I had a common negative for my PV banks and a common negative AFTER the shunts. I was concerned about circulating currents with the parallel conductors but it's DC so where would the induction be, anyway?

Had to split the PV bank negatives. One set got the nice negative splitter bar and the other set got a tape balled split bolt. That fixed the problem with the metering only to find I had my negatives through the wrong shunts and my positives through the FM 80s OK. It seems I ohmed out the pairs coming out of the pipe but separated and matched them incorrectly to the FN-DC shunts. After almost a year, just a few nights ago, I finally got around to reversing the shunt feeds and straightening it out the way I wanted it in the first place. :)

I spent 35 years troubleshooting much more complex grid protection and control wiring schemes and I was embarrassed for myself with this simple job. :)
larrywa
Forum Guru
 
Posts: 351
Joined: Thu Jun 25, 2015 11:25 am
My RE system: FlexPower Two
2 x GVFX3648s,
2 x FM80s,
FNDC w/3 shunts,
Mate3 v3.015.005 (works excellent!)
Hub 10.3,
PV:1000W east@45, 600W west@45, 2400W south@19 deg.
Battery:48v @ 130Ahr Crown batteries, deep cycle <$380 for 6.25kWh

ISY994i HA, Insteon, X10, Philips Hue, MiLight bulbs & RGBW strips
WebControl 8 as weather station stuffing
ISY994 variables via REST interface

Raspberry Pi3 x 2, Pi1 B+

Re: Resolution

Postby JRHill on Fri Sep 25, 2015 6:43 pm

The company I work with takes support requests from users of the free version because, buried within all the requests, are always some that are really valid and can affect everyone (it's part of the open source, community spirit). I am sure that while the Outback folks roll their eyes over errors like I made, they also find valid issues to be addressed. Its the old "there are no stupid questions" thing.

So it's important to post issues/problems in these forums. It's just as important to post the resolution.

Best,
Jim
User avatar
JRHill
Forum Guru
 
Posts: 336
Joined: Thu Feb 17, 2011 12:12 pm
Location: South central WA
My RE system: -House: FM 80, VFX 3648, FlexnetDC, FlexWare xformer, Mate 3 / Hub, WattPlot/, 2925w SunTech 195, Trojan L16RE-B Batteries. Backup 1: Champion 75531i 3100, backup 2: 11kw Miller Bobcat;
-Well: Grundfos 11-SQF-2 pump, controller & AC switch (CU200, IO101), Morningstar 15a/48vdc Controller, 780w SunTech 195, Trojan golf cart batteries.
-All running since July '11 with no critical problems.

Re: Resolution

Postby JRHill on Fri Sep 25, 2015 6:59 pm

And adding to that last comment about community: OpticsRE. Hey Outback, open source it under the GPL license. Get a bunch of development and maturity. And when the time comes, you have the free and the paid versions - which I'm sure is coming.
User avatar
JRHill
Forum Guru
 
Posts: 336
Joined: Thu Feb 17, 2011 12:12 pm
Location: South central WA
My RE system: -House: FM 80, VFX 3648, FlexnetDC, FlexWare xformer, Mate 3 / Hub, WattPlot/, 2925w SunTech 195, Trojan L16RE-B Batteries. Backup 1: Champion 75531i 3100, backup 2: 11kw Miller Bobcat;
-Well: Grundfos 11-SQF-2 pump, controller & AC switch (CU200, IO101), Morningstar 15a/48vdc Controller, 780w SunTech 195, Trojan golf cart batteries.
-All running since July '11 with no critical problems.


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