Fox ESS on-grid inverter

Register map(s) for this device, with a note of how far each has been checked. Addresses are 0-based, as on the wire. Scale and byte order are confirmed only at the hardware-verified rung.

coherence-checked

Round-trips through a real Modbus stack with no overlapping addresses and a word-order-sensitive codec — the map is internally coherent and wire-decodable. Does NOT prove byte-order or scaling match a real device: the emulator is seeded from the map's own types, so a uniformly wrong byte-order still round-trips. Only hardware-verified confirms byte-order/scale on the wire.

point	address (0-based)	type	scale
master_state	10500	U16	1
grid_yield_today	10503	U16	0.1
grid_yield_total	10504	U32BE	0.1
feed_in_power	10506	I16	1
output_power	10507	I16	1
load_power	10508	I16	1
bat_power	10509	I16	1
grid_volt_r	10700	U16	0.1
grid_current_r	10701	I16	0.1
grid_freq_r	10702	U16	0.01
grid_power_r	10703	I16	1
grid_volt_s	10704	U16	0.1
grid_current_s	10705	I16	0.1
grid_freq_s	10706	U16	0.01
grid_power_s	10707	I16	1
grid_volt_t	10708	U16	0.1
grid_current_t	10709	I16	0.1
grid_freq_t	10710	U16	0.01
grid_power_t	10711	I16	1
pv1_volt	10800	U16	0.1
pv1_current	10801	U16	0.1
pv1_power	10802	U16	1
pv2_volt	10803	U16	0.1
pv2_current	10804	U16	0.1
pv2_power	10805	U16	1
charger_temp	11200	I16	1
inv_temp	11201	I16	1
ambient_temp	11202	I16	1
bat1_volt	11500	U16	0.1
bat1_current	11501	I16	0.1
bat1_power	11502	I16	1

link settings as documented (unverified): RTU; default 9600 8N1; unit ID 1; FC 03,04,06,16,69

bench facts as documented (unverified)

terminals	RS485
max registers/read	125
model register	10020
serial register	10036
firmware register	10055
doc revision	V1.02

field reports — community-sourced, unverified (checked 2026-06-11)

For some inverter firmware versions, Fox ESS changed the scale of specific registers (e.g., reading 1600 instead of 1.6), requiring integration adjustments based on the active firmware version. [source]
Firmware updates (such as Master update to 2.23 on H3 series) can break Modbus communication or cause specific registers to return invalid errors, requiring integration re-configuration or manual file adjustments. [source]
confirmed: baud_rates [9600], default_baud 9600, default_unit_id 1, framing [RTU], parity N, stop_bits 1 — confirmed by FoxESS Modbus Communication Protocol Guide (V1.02) which specifies RS485 asynchronous mode with 9600 bps, no parity, 8 data bits, and 1 stop bit
confirmed: identification registers (model_register 10020, serial_register 10036, firmware_register 10055) — confirmed by FoxESS Modbus Protocol Guide where 10020 is ModuleName, 10036 is SeriesNumber, and 10055 is MasterVersion
confirmed: register map summary (master_state @ 10500, grid_yield_today @ 10503, grid_yield_total @ 10504, feed_in_power @ 10506, grid_volt_r @ 10700, grid_current_r @ 10701, grid_freq_r @ 10702, pv1_volt @ 10800, pv1_current @ 10801, pv1_power @ 10802, charger_temp @ 11200, inv_temp @ 11201, bat1_volt @ 11500, bat1_current @ 11501, bat1_power @ 11502) — confirmed by FoxESS Modbus Protocol Guide register definitions

The trust ladder

Each rung states what it proved and what it did not. Gray until proven; green is earned by hardware only.

generated — A prompt produced it. Unproven — anyone can regenerate this.
structure-verified — Decode path is structurally sound (addresses, widths, finite values). Does NOT prove word order or scaling.
coherence-checked — Round-trips through a real Modbus stack with no overlapping addresses and a word-order-sensitive codec — the map is internally coherent and wire-decodable. Does NOT prove byte-order or scaling match a real device: the emulator is seeded from the map's own types, so a uniformly wrong byte-order still round-trips. Only hardware-verified confirms byte-order/scale on the wire.
hardware-verified (software-key) x1 — Matched a real device with operator-attested readings as ground truth — the only rung that confirms word order + scaling on the wire.

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