Power flow delta: in vs. out of battery seems high

Discussion about the OutBack OpticsRE system monitor

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Mike Curran
Forum Emperor
Posts: 2284
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied VFXR3524A-01's series stacked, replaced GVFX's (2020)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS. Tigo ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB inverter/charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input from 14 Talesun 275W, Enphase M215 microinverters

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Power flow delta: in vs. out of battery seems high

Post by Mike Curran »

With solar input, my Optics dashboard power flow diagram always shows a pretty large difference between power into my battery and power out (see screenshot where the difference is about 600 watts). I recognize that some of that difference could be attributable to DC loads not flowing through either shunt, but my unmonitored DC loads are extremely small, on the order of 10 watts or so. But the battery graph showing kwh in vs. out in any given hour only reflects about 60 watts difference, nowhere near the 600 watts on the power flow (same screenshot).

Is it a coincidence that these 2 values differ by a factor of ten, or is there something else I'm missing? I thought I used the same 500A:50mV shunt for both. I'm pretty sure the inverter shunt is that ratio but not so sure (now) about the CC shunt...

My system has been running fine since installing the FNDC in 2016, but this discrepancy is bothering me. Any ideas?
20210315_125636.jpg
https://smart.tigoenergy.com/p/pZXn7SZQyO45?date=2021-04-19
https://enlighten.enphaseenergy.com/public/systems/Hctc107221
raysun
Forum Emperor
Posts: 4624
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
Honda EU7000is gas fuel generator

Re: Power flow delta: in vs. out of battery seems high

Post by raysun »

I've scratched by head over the power flow diagram always showing what's going to the loads (AC) always equalling what's being drawn from the battery (DC). In my world, that's impossible due to power factor on the AC side, yet there it is.

Perhaps a more nuanced view is to look at what's being read off the shunts at battery full charge.

It looks like 2.0kW AC load is being serviced by 1.58kW from the battery, or more likely a combination solar harvest and battery draw.

I wonder if some of the PV current transits the battery bus without actually entering the battery via the shunt?
Mike Curran
Forum Emperor
Posts: 2284
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied VFXR3524A-01's series stacked, replaced GVFX's (2020)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS. Tigo ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB inverter/charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input from 14 Talesun 275W, Enphase M215 microinverters

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: Power flow delta: in vs. out of battery seems high

Post by Mike Curran »

I wonder if some of the PV current transits the battery bus without actually entering the battery via the shunt?
I considered that but the only place (that I can see, anyway) there's a common negative connection is at the battery and after each shunt. Looks like this:
20210315_165255.jpg
https://smart.tigoenergy.com/p/pZXn7SZQyO45?date=2021-04-19
https://enlighten.enphaseenergy.com/public/systems/Hctc107221
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