EG4 Community Forum - Recent Topics

Why is AC charging occurring?

gtsquires — Sun, 26 Jul 2026 20:31:50 +0000

As the chart below shows, all night long my batteries repeatedly charge briefly from the grid, then discharge. The pdf shows my settings and that AC charging is disabled. Why is this happening? I have an 18 KPV inverter and 2 - 280Ah indoor wall-mount batteries.

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Correct wiring for Flexboss 21 with two 314ah batteries

nothing2crazy — Thu, 23 Jul 2026 16:16:25 +0000

Quick question, with 1 Flexboss and 2 314ah batteries, is it adequate to directly connect each battery to the lugs on the inverter, or should the master battery be connected to the 4 lugs on the inverter with parallel cables to the second battery?

EG4 12000XP - Can GRID Input Work Without a Utility Neutral?

YRV93 — Wed, 22 Jul 2026 17:54:57 +0000

Hello everyone,

I hope someone from the EG4 technical team or an experienced installer can help me with a question about the EG4 12000XP.

I have carefully read the EG4 12000XP User Manual, especially section 8.4 (Neutral-Ground Bonding). I understand that the AC input and AC output share a common neutral, the neutral is never disconnected internally, and the inverter can create the Neutral-to-PE bond using the N-PE Connect setting if required.

However, my installation is very unusual, and I have not been able to find any information about this situation.

The system will be installed in a rural area of Cuba. The utility company does not provide a neutral conductor or an equipment grounding conductor. Only two energized conductors come from the utility line.

For many years, the house has been powered through an old tap-changing transformer/autotransformer located before the main electrical panel. The purpose of this transformer is not isolation but voltage regulation because the local utility voltage is very unstable.

One incoming utility conductor passes directly through the transformer, while the other is connected to one of several taps to decrease the output voltage. After leaving this transformer, the house receives approximately 127–130 VAC to power all the household loads. There has never been a dedicated neutral conductor or an earth grounding conductor in the installation.

I am planning to install an EG4 12000XP with batteries and solar panels, and I would like to eliminate the old transformer if possible and connect the utility directly to the inverter.

My questions are:

1. Can the GRID input of the EG4 12000XP operate with only L1 and L2 connected, without a utility neutral conductor?

2. If there is no utility neutral available, should the GRID Neutral terminal remain unconnected?

3. If this configuration is not supported, what is the manufacturer's recommended solution?

4. Would an isolation transformer or another type of transformer be required?

5. If the N-PE Connect function is enabled, can the inverter create the proper system neutral for the AC output even though the utility supply does not include a neutral conductor?

6. Is there an official wiring diagram or application note for this type of utility supply?

I would really appreciate any guidance from the EG4 engineering team or anyone who has experience with this type of installation.

Thank you very much for your time.

Dedicated PowerShed Device Separation for Inspection

twistedroutes — Wed, 22 Jul 2026 15:23:03 +0000

For a compliant installation of an ESS one must follow the specification for device separation, however EG4 documentation is internally inconsistent. Specs show separation requirements however the installation diagrams do not observe this. For example:

EG4 diagrams for the ESS show a conduit box directly on top of batteries and directly below the inverter. this space, according to the documentation should be 19.75" but the conduit box is < 10 inches - so this can not be accomplished
EG4 diagrams illustrate and document " In the following diagrams, units are spaced 6.69 in. (170 mm) apart " ( eg4 document link ) and clearly illustrates the inverter atop the conduit box, atop the battery - also making the horizontal spacing of the inverter < 19.75"

In my (completely off-grid) installation I will have 4-6 EG4 280 ah wallmount batteries and 2 12000XP inverters a generator distribution panel and a loadcenter/main panel (combining inverter outputs). Further more, if I were to meet this separation requirement in a room or a dedicated "shed", floor to ceiling needs to be ~ 9'2".

Has anyone had any practical experience in deploying such a configuration (permitted) or has any stated deviance/variance from EG4? To pass inspection the ESS must observe all clearances by the vendor, so any deviance/variance would need to be documented by EG4.

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note: I contacted EG4 "support" who redirected me to "technical support" but would not forward my email to them, or provide me with an email to contact them. I'll have to explain this over the phone to "technical support" but this post will be useful to direct them to - and hopefully answer this for someone else.

Basic min & max voltage logic

JamCandles — Fri, 17 Jul 2026 16:32:25 +0000

In the next update, can we get basic voltage logic added to supplement the SOC calculations? The last update did not resolve SOC wander, anecdotally it got a bit worse in my observation as they consistantly wander low now. Within a few weeks, unless I waste grid energy to top them, my 4-pack of wallmounts will end up with 30-40% difference in reported SOC and well below real charge level.

Real life example - I have right now:
Battery 1 - 46% SOC shown
Battery 2 - 34% SOC shown
Battery 3 - 55% SOC shown
Battery 4 - 62% SOC shown
Entire pack is at 52.62V with effectively zero load (solar is just covering loads)

Looking at the EG4 discharge curve, there is no possible way, with any load, to hit that voltage and SOC combination. If the firmware applied basic voltage logic just to limit the SOC wander, while it wouldn't be exactly accurate, it would at least keep them in a reasonable range.

To be clear, topping them weekly does keep them within EG4's stated 10% acceptable wander. But that wastes grid usage or solar production every week every time.

Very warm Flexboss 21

nothing2crazy — Thu, 16 Jul 2026 20:11:18 +0000

I'm wondering what is too hot for a Flexboss 21. I've noticed recently on warm days when the temperature in our garage reaches 80° F, the front of the Flexboss is warm and the top ventilation is too hot to touch. I've checked the data history on the monitoring website and some of our "Tradiator" values have reached as warm as 68°C (155°F). These seems to happen shortly before the fans spin up in the morning and shortly after they spin down in the evening. 155° seems awfully warm for the fans to have spun down.

Anyone from the UK who can clear this up?

lyrawinslow — Tue, 14 Jul 2026 10:02:45 +0000

Hi everyone,

I know this topic is a bit old, but I was reading about the plan to make solar panels mandatory on new homes in England from 2027. Since 2027 isn't that far away now, I was wondering what the situation is today.

I'm interested in the UK solar market, and I'd like to understand what it's actually looking like on the ground. Are builders already including solar as standard? Has it increased the price of new homes, and roughly how much does a typical solar setup cost these days?

I'd really appreciate hearing from someone in the UK or anyone working in the industry, because most of the articles I find are from last year. Thanks!

Pre-purchase Q: Flexboss21/Gridboss register write-endurance + split 400A / dual-200A-panel setup

Solar_Rob — Mon, 13 Jul 2026 18:59:46 +0000

Looking at a FlexBOSS21 + GridBOSS system but haven't pulled the trigger yet — want to work through a few Modbus register questions first since my planned control setup depends on the answers.

One thing up front so nobody assumes the usual setup: my service is 400A, split into two independent 200A panels that both feed toward the meter. The FlexBOSS21/GridBOSS would land on one of those 200A panels (the backed-up one). The GridBOSS's own CTs only see that panel — they have no visibility into the second 200A panel at all, since it's a completely separate panel that only reconciles with the GridBOSS's panel out at the meter. So from the inverter's point of view, any load on that second panel is indistinguishable from grid export. I'd be adding an Acrel ADL400 on that second panel to actually see its load, and feeding that into a local Modbus RTU loop (RS485, no dongle, no cloud) to try to serve both panels from solar/battery before buying anything from the grid, without exporting stored battery energy in the process.

Working off the 18kPV-12LV Modbus doc plus the community FlexBOSS21 register map (@snarfattack's ESPHome work has been a huge help here) since I know a full official register map for FlexBOSS21/GridBOSS isn't out yet.

Questions, roughly in order of "this determines whether the whole plan works":

- **Registers 138–143** (the 0.1%-resolution *PowerCMD registers — ChargePowerPercentCMD, DischgPowerPercentCMD, ACChgPowerCMD, ChgFirstPowerCMD, ForcedDischgPowerCMD, ActivePowerPercentCMD) — anyone know if these are RAM or if they write through to EEPROM/flash? I'd be hitting these roughly every 15s (~5,700 writes/day) to track the second panel's load, and that's a lot of writes if they're not meant for it.

- Does **Charge Priority** (reg 141) pull PV away from backed-up loads to hit its target, or does it only grab PV that's already surplus to load demand?

- What's the **kW reference for 100%** on the 138–143 block for FlexBOSS21 specifically?

- Is **ForcedDischgPowerCMD** (reg 142) the *total* discharge target, or an *add-on* to whatever's already discharging natively for EPS/backed-up loads?

- Is **10% really the floor for EOD** (reg 105) on-grid like the 18kPV doc says, or can FlexBOSS21 go lower?

- Any general guidance on **write endurance** for holding registers — and specifically for reg 103 (MaxBackFlow)? Since the second panel is invisible to the GridBOSS anyway, my plan is to treat MaxBackFlow as a static ceiling rather than something I write dynamically. Sanity check that's the right call?

- Has anyone here actually run a **GridBOSS-invisible second panel** on a split 400A service like this? Trying to figure out if I'm about to hit a known edge case or if this is well-trodden ground.

Will post back with whatever I find out / whatever I end up testing — seems like it'd help anyone else with a similar split-panel setup.