I have 12KW solar connected to an 18kpv and a couple of 100Ah batteries that provides backup to a critical loads panel. In an outage/backup scenario it does not provide enough power output or capacity for whole home backup.

To solve this I thought I would get a gridboss and a flexboss along with 2 x 314Ah (16kW) batteries. Connect gridboss to main panel for whole home backup instead of just the critical loads panel, connect flexboss and 18kpv to gridboss, connect one battery to flexboss and one to 18kpv for load balance.  This should double output power and significantly increase capacity. Maybe add more battery capacity in the future.

I got a quote from an EG4 installer for the gridboss, flexboss, 2 batteries, and install for approx $36k

I also got a quote from a different company to install an aGate and 2 x 15kW Franklin batteries (ac coupled to the 18kpv) for approx $32k. This also provides 20kW of output power as well as the same capacity, all configured for whole home backup.

I'd heard Franklin was expensive so I was a bit surprised the Franklin solution turned out to be actually cheaper than EG4 solution, and seemed a lot less work removed link It seems EG4 equipment is pretty reasonable priced but the installation must be way more complex because the overall cost is crazy?

I'm kind of stuck deciding which way to go, even considered just buying a generac and connect to the 18kpv because that's actually the cheapest and simplest (but not optimal) option!

Has anyone got experience of Franklin batteries used with EG4 inverters?  I am leaning this way at the moment.

Anyway, any advice or feedback is appreciated.

When the battery reserve hits 20%, the inverter cuts discharge and switches to paid grid power. This happens around 2:00 AM. From that point on, I'm paying. And when the sun comes up, the inverter insists on recharging a buffer before releasing energy back to the house. So the grid bill keeps running until 7 or 8 AM with panels already producing above me. That's not a technical limitation. That's a delivery gap in the system's logic.

The manual workaround was simple: if tomorrow's forecast looked strong, I'd wake up at 5:00 AM and override the reserve limit to 0%, forcing the battery to drain just enough to meet sunrise perfectly. It made a noticeable difference on the bill. But one bad call on a cloudy day meant zero battery, and if the grid went down, zero house. The risk tolerance was unsustainable without automation.

So I built the brain.

The goal was a predictive engine that could make that call autonomously: is tomorrow's solar production reliable enough to justify releasing the reserve? Yes or no, with real data behind it.

The first approach used NASA irradiance data. Failed immediately. Timezone misalignment between UTC and my local zone made the solar curve completely unusable. Migrated to Open-Meteo and built an astrophysical filter that zeroed out below-horizon hours mathematically.

The second approach used Meta's Prophet model trained on months of my own production data. Also failed. I had recently doubled my panel capacity with a second inverter, and Prophet kept averaging against the old baseline. My system was producing 6,000W and the model stubbornly forecasted 2,000W. It couldn't adapt to an infrastructure change, which is a familiar problem for anyone managing environments that evolve faster than the models tracking them.

I'll be honest, I shelved the project for a while. Bought more batteries as a brute-force fix to survive the night. But the operational inefficiency kept nagging at me, so I came back to finish it right.

The solution was to abandon statistics entirely and build a physical scaling engine. Instead of training a model on historical averages, the system reads the last 7 days of real panel output to detect proven peak capacity, extracts thermal efficiency against the climate ceiling, and discounts tomorrow's cloud cover from the forecast API. Physics over pattern-matching. No training set, no hyperparameters. The model calibrates itself every night.

The output is a triple-curve forecast generated nightly: actual production (orange), ideal clear-sky potential (dotted bell), and a realistic prediction adjusted for every cloud in tomorrow's weather model (blue). The accuracy has been remarkably precise.

The decision engine is already built and tested. It doesn't run on a simple timer. It calculates three variables in real time: current household consumption, remaining battery capacity, and the scheduled sunrise hour. If the stored energy is enough to bridge that gap, it sends the release command. If not, it holds. A decision engine, not an alarm clock. I've been validating it by pushing automated Telegram notifications every time the system triggers a decision, and it works 

The only remaining piece is the Solar Assistant integration to execute the actual inverter parameter change automatically. Once that connection is live, the entire cycle runs without human intervention.

Beyond my specific use case, this opens the door to something bigger: automatically deciding when to consume battery and when to hold it, so you either pay less or use 100% of your installed capacity instead of letting the inverter's conservative defaults leave energy on the table.

I'm sharing the repo here. The README covers everything, and getting started is straightforward: just upload your inverter data. I left my own export files in as examples so you can see the expected format.

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Contributions welcome.

What I do have is the green terminal block above.

My questions:
1. Are COM1 and COM2 on the green terminal block the RS485 A+ and B− lines?
2. If so, which is A+ and which is B−?
3. Is there any conflict with the batteries already using BAT COM, or are these completely separate?

Goal is to connect a USB RS485 adapter to the terminal block and read inverter data locally via Modbus.

And the Flexboss 21 will not register any of my PV.

Worked with tier 1 support with no improvement today. Tried resetting/restarting everything with no improvement. 

Anyone else have this issue or suggestions?

Symptom & troubleshooting, This is a new, recently installed system that the PV never starts up. PV panels can be configured as two banks or one complete bank. Initially tried two banks connected to PV inputs 2 & 3 where PV 2 had ~220VDC on it's input and PV 3 had ~ 180VDC. The MPPT's would never start up, i.e. no PV current pulled by inverter on either input (measured with external voltage and current meter). Also, no PV voltage displayed in any PV (1,2,3) Data, Chart, Voltage measurement. I can physically measure voltage at each PV 2 & 3 inverter input terminals but yet no voltage measured by inverter other than small accuracy related fluctuations. In knowing that this inverter has a MPPT start up voltage of 200VDC. The thought was that I was right at it's minimum so I also lowered the Start PV Voltage to 170V. Still no go. I then configured the two strings into one complete string. This now has a voltage of ~380 - 400VDC. I then transferred this to MPPT 1's inputs. This did not work any better and I still could not see any voltage on PV 1's Data Voltage measurement. I have checked all settings under the maintenance tab and everything appears correct. Even the advanced settings -

Note that other than the above PV issue, all else appears to be working. Batteries can supply power to EPS loads & can be charged from grid.

Eric - I can DM you with system access and other information if you want to look at it.

eg4electronics.com says:

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Do i need to make a setting change on my gridboss or inverters?

Thanks

2026-03-29

• Based on FAAB-2626/2525.
• Match LCD V25.
• 1. Improved. New England Grid Profile — added regional grid profile support for New England configurations, with Voltage-Active mode disabled by default.
• 2. Improved. Added RS485 BUS communication support on the Meter485 port for PPL Electric installations.
• 3. Improved. LUMA Grid Profile: Voltage-Active Power mode enabled by default.
• 4. Improved. HECO Grid Profile: Frequency-Active Power mode enabled by default; under-excited reactive power set as default.
• 5. Improved. Optimized charging power limitations when PV power is unbalanced across inverters in a parallel system.
• 6. Improved. LCD phase setting labels updated from R/S/T to A/B, B/C, C/A （LCD V25）.
• 7. Improved. Update fan logic to start fans at a lower temperature to optimize heat dissipation.
• 8. Bug Fixes. Fixed repeated switching between on-grid and off-grid modes on the secondary inverter triggered by off-grid cut-off voltage in parallel shared-battery and lead-acid battery mode.
• 9. Bug Fixes. Reduced probability of repeated state switching between PVBatGridOn and PVChgGridOn.
• 10. Bug Fixes. Fixed the inability to exit on-grid AC couple charging state and switch to battery discharge when load exceeds AC couple power in a parallel system.

2026-03-29

• Based on FAAB-2626/2525.
• Match LCD V25.
• 1. Improved. New England Grid Profile — added regional grid profile support for New England configurations, with Voltage-Active mode disabled by default.
• 2. Improved. Added RS485 BUS communication support on the Meter485 port for PPL Electric installations.
• 3. Improved. LUMA Grid Profile: Voltage-Active Power mode enabled by default.
• 4. Improved. HECO Grid Profile: Frequency-Active Power mode enabled by default; under-excited reactive power set as default.
• 5. Improved. Optimized charging power limitations when PV power is unbalanced across inverters in a parallel system.
• 6. Improved. LCD phase setting labels updated from R/S/T to A/B, B/C, C/A （LCD V25）.
• 7. Improved. Update fan logic to start fans at a lower temperature to optimize heat dissipation.
• 8. Bug Fixes. Fixed repeated switching between on-grid and off-grid modes on the secondary inverter triggered by off-grid cut-off voltage in parallel shared-battery and lead-acid battery mode.
• 9. Bug Fixes. Reduced probability of repeated state switching between PVBatGridOn and PVChgGridOn.
• 10. Bug Fixes. Fixed the inability to exit on-grid AC couple charging state and switch to battery discharge when load exceeds AC couple power in a parallel system.

2026-03-29

• Based on FAAB-2626/2525.
• Match LCD V25.
• 1. Improved. New England Grid Profile — added regional grid profile support for New England configurations, with Voltage-Active mode disabled by default.
• 2. Improved. Added RS485 BUS communication support on the Meter485 port for PPL Electric installations.
• 3. Improved. LUMA Grid Profile: Voltage-Active Power mode enabled by default.
• 4. Improved. HECO Grid Profile: Frequency-Active Power mode enabled by default; under-excited reactive power set as default.
• 5. Improved. Optimized charging power limitations when PV power is unbalanced across inverters in a parallel system.
• 6. Improved. LCD phase setting labels updated from R/S/T to A/B, B/C, C/A （LCD V25）.
• 7. Improved. Update fan logic to start fans at a lower temperature to optimize heat dissipation.
• 8. Bug Fixes. Fixed repeated switching between on-grid and off-grid modes on the secondary inverter triggered by off-grid cut-off voltage in parallel shared-battery and lead-acid battery mode.
• 9. Bug Fixes. Reduced probability of repeated state switching between PVBatGridOn and PVChgGridOn.
• 10. Bug Fixes. Fixed the inability to exit on-grid AC couple charging state and switch to battery discharge when load exceeds AC couple power in a parallel system.