Skybox drawing on battery and throttling solar

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Joined: Wed Jun 26, 2024 9:48 am
My RE system: Skybox, HAB 7.5 KW battery, 4.3KW solar array

Skybox drawing on battery and throttling solar

Post by JEsdorn »

Yesterday, the grid was down for 12 hours. During that time, the Skybox inverter didn't fully cover the .5 KW consumption of my house even though there was at least 3KW solar available. Instead, it drew .2KW from the battery and only covered the balance .3KW from the solar. As a result, the battery ended up 1/3 discharged at the end of the day.

In addition, the Skybox didn't recharge the battery right away after the grid came back on but waited until shortly before midnight to do so. What is wrong?

Many thanks for any help you can provide!
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Mike Curran
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Posts: 3325
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof (2007/2017):
- 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)
- 24 (2x12) 235W Lightways panels with Enphase M215 microinverters plus 6 - 275W Talesun panels, also with M215s, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Trina Solar 270W in series (DC array input to SB inverter/charger), installed 3/5/24 (replaced original 2019 Talesun DC array)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input from 14 Talesun 275W (manually switched during outages), Enphase M215 microinverters

Battery systems operate in grid-tied, net metering w/backup mode
All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: Skybox drawing on battery and throttling solar

Post by Mike Curran »

Skybox will not (re)charge the battery until voltage falls to the rebulk setpoint, and/or the next morning when the sun comes up. You can manually start a rebulk by hitting the "Reset" button from the web interface (or at the local panel).

I dropped the grid yesterday just to see how mine would perform today in restoring the battery. Here's the graph with SOC:
Screenshot_20240628_145727_Samsung Internet.jpg
PV brought SOC up from 72% to 95% over 6 hours - it took that long to bring battery voltage up from a minimum of 52.3V to my absorb setpoint and hold it there for 10 minutes absorb time. Still didn't make 100% SOC.Here's the corresponding KW graph, FWIW.
Screenshot_20240628_152031_Samsung Internet.jpg
I didn't try restoring grid before midnight to see when it might start recharging the battery but probably not at all unless battery voltage decayed to rebulk setpoint.

I was planning to respond sooner but my internet access got lost (a tree fell on the fiber line up the street, also caused a short grid outage).
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