The power register reads zero even when the inverter is running. Why?

The SAJ H2 communicates via the eSolar AIO3 dongle. If the dongle has lost its Wi-Fi or Ethernet link, the Modbus TCP socket will accept connections but return zero or stale values. Check the dongle's LED status and confirm it holds a stable IP address before re-polling.

Phase current registers A, B, and C all return identical values. Is that normal?

Identical phase currents are only expected on a perfectly balanced three-phase load. If you see the same non-zero value on all three registers, verify that the Modbus TCP client is reading the correct register addresses (16434, 16441, 16448) and that the inverter firmware supports the three-phase current registers for your specific H2 variant.

The cumulative energy register wraps around unexpectedly. What is happening?

The energy register is a uint32, so it rolls over at 4,294,967,295 watt-hours (roughly 4.3 GWh). For most residential sites this will not occur for many years, but if the register appears to reset, check whether the inverter firmware has been updated and reset the energy counter, or whether a gateway reconnection caused the type to be read as 16-bit instead of 32-bit.

The gateway connects but values are wildly out of range. What should I check?

The SAJ H2 protocol stores several measurements as signed int16 values with an implicit scaling factor applied by the inverter firmware. If your portal displays raw register counts, confirm the template's data type for each register (int16 for power and currents, uint32 for energy) is applied correctly. A missing scale factor or incorrect type will produce values that appear many times too large or too small.

Free Modbus template: SAJ H2 Series Hybrid Solar Inverter (grid)

The SAJ H2 Series Hybrid Solar Inverter is a three-phase hybrid PV inverter for residential and light-commercial on-grid and off-grid solar installations. This Modbus TCP template reads the inverter's grid interface: instantaneous grid exchange power, per-phase AC currents on phases A, B, and C, and cumulative grid energy. Together these five registers give installers and asset managers a clear, continuous view of how the H2 Series Hybrid Solar Inverter interacts with the utility grid, enabling accurate energy accounting and fault detection without additional metering hardware.

Name	Address	Function	Type	Unit	Access
power Instantaneous grid exchange power, signed, watts.	16557	FC03	int16	W	R
currents_a AC current on grid phase A, signed, amperes.	16434	FC03	int16	A	R
currents_b AC current on grid phase B, signed, amperes.	16441	FC03	int16	A	R
currents_c AC current on grid phase C, signed, amperes.	16448	FC03	int16	A	R
energy Cumulative energy exchanged with the grid, watt-hours.	16637	FC03	uint32	Wh	R

SAJ H2 Series Hybrid Solar Inverter (grid)

Overview

Use cases

Installation

Things to watch for

Registers (5)

Working with Modbus in your projects?

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