High battery voltage w/ AC coupled system

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Mike Curran
Forum Emperor
Posts: 1817
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 GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy 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 (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

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

High battery voltage w/ AC coupled system

Post by Mike Curran » Sat Mar 14, 2020 8:01 am

My Skybox system with Simpliphi batteries consistently runs above 54 volts. This is too high for these batteries. Screenshot from yesterday showing voltage trend and max at one point (63.65!!!):
Screenshot_20200314-104717.jpg
I have float charge disabled along with these battery settings:
Screenshot_20200314-110412.jpg
Fyi, my AC coupled array combined with the DC array power output sometimes exceeds the Skybox's 5kw export (to grid) limit. Could this be causing the overvoltage? My understanding is with an AC-coupled system, when the grid is down the Skybox will prevent overcharging the battery by raising the output frequency so that the AC-coupled inverters disconnect. But what happens when the grid is still up and SB power input exceeds its export capability?

I also have a tech support request in to OB for this issue.

Thanks for any feedback! - Mike
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

fcwlp
Forum Czar
Posts: 545
Joined: Wed Jan 22, 2020 9:40 am
My RE system: GS8048A, FM80 w/3,600 W PV Fixed, FM80 w/2,700W on Zomeworks tracker, Mate3, 24 Trojan 2V L16 1100AH @ C20, Grid-Tied with Kohler 14RESA LPG Generator and MEP-803 Diesel if needed
I also install and maintain grid-tied and off-grid systems, details will be given for these system if required
Location: 80 miles NE of Phoenix at 5500'

Re: High battery voltage w/ AC coupled system

Post by fcwlp » Sat Mar 14, 2020 10:13 pm

Mike, any idea of what caused the start of the ramp up to 63+ volts? It was holding steady at ~54V prior to that even with the solar peaking during the 54V period.

Mike Curran
Forum Emperor
Posts: 1817
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 GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy 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 (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

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

Re: High battery voltage w/ AC coupled system

Post by Mike Curran » Sun Mar 15, 2020 4:37 am

fcwlp wrote:
Sat Mar 14, 2020 10:13 pm
Mike, any idea of what caused the start of the ramp up to 63+ volts? It was holding steady at ~54V prior to that even with the solar peaking during the 54V period.
No, but it looks like it went into an absorb cycle based on the peak charge data point shown here:
Screenshot_20200315-072106.jpg
And during the previous hour voltage reached the minimum for the day at 53.6 but that's nowhere near the rebulk setpoint of 51 volts.
Screenshot_20200315-072408.jpg
When the load trace (blue) goes negative, that's showing the effect of AC coupling (= [load] minus [AC PV]) and at the point where voltage starts to go up, the "negative load" never goes below 2.06kw (average for that hour [edit] = 1.27kw):
Screenshot_20200315-073534.jpg
Last edited by Mike Curran on Tue Mar 17, 2020 8:13 am, edited 1 time in total.
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

Mike Curran
Forum Emperor
Posts: 1817
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 GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy 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 (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

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

Re: High battery voltage w/ AC coupled system

Post by Mike Curran » Sun Mar 15, 2020 8:32 am

Around 3:15 pm that day (a tad later than when the battery voltage spike occurred) the grid voltage went out of range, which should've disconnected the Skybox from grid and permitted it to alter its AC output frequency to prevent the grid-tied microinverters from overcharging the battery...
Screenshot_20200315-112331.jpg
Around 3:23 event history shows "Grid (not greed :grin: ) is good".

FYI, this out of range condition occurs here often in the spring as the weather warms and grid voltage rises as a result of the drop in electric heating load in the neighborhood (I live in an all-electric community with '50s era baseboard heating).
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

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