foxess-feeder

Polls a FoxESS H3 PRO inverter via Modbus TCP every 10 seconds and writes readings to InfluxDB 2.

Registers polled

Field	Description	Unit
battery_soc	Battery state of charge	%
battery_voltage	Battery voltage	V
battery_temp	Battery temperature	°C
battery_power	Battery charge/discharge power (negative = charging)	kW
inverter_temp	Inverter temperature	°C
load_power	House load power	kW
grid_ct	Grid import/export via CT clamp (negative = export)	kW
gen_load	CT2 external generation (e.g. separate solar inverter)	kW
pv1_power	PV string 1 power	kW
pv2_power	PV string 2 power	kW

Requirements

• FoxESS H3 PRO inverter with Modbus TCP enabled (port 502)
• InfluxDB 2 instance
• Rust toolchain (for building)

Configuration

All configuration is via environment variables.

Variable	Required	Default	Description
FOXESS_MODBUS_IP	Yes	—	Inverter LAN IP address
INFLUXDB_URL	No	http://localhost:8086	InfluxDB base URL
INFLUXDB_TOKEN	No	foxess-local-token	InfluxDB auth token
INFLUXDB_ORG	No	home	InfluxDB organisation
INFLUXDB_BUCKET	No	inverter	InfluxDB bucket
DEBUG	No	unset	Print register values to stdout each poll

Building

cargo build --release

Cross-compile for Raspberry Pi (from Mac M1)

brew install messense/macos-cross-toolchains/aarch64-unknown-linux-gnu
rustup target add aarch64-unknown-linux-gnu
cargo build --release --target aarch64-unknown-linux-gnu

Binary will be at target/aarch64-unknown-linux-gnu/release/foxess_feeder.

Running

FOXESS_MODBUS_IP=192.168.0.x ./foxess_feeder

With debug output:

DEBUG=1 FOXESS_MODBUS_IP=192.168.0.x ./foxess_feeder

On startup the program prints one line once the first successful poll and InfluxDB write completes:

Connected to inverter and InfluxDB. Polling every 10s.

Behaviour

• Reconnects automatically if the Modbus TCP connection drops (30s delay between attempts)
• InfluxDB write failures are logged but do not trigger a reconnect
• Each Modbus read has a 15s timeout to handle half-open TCP connections
• Writes to the inverter measurement in InfluxDB line protocol

Running as a service on Raspberry Pi

Create /etc/systemd/system/foxess-feeder.service:

[Unit]
Description=FoxESS inverter data feeder
After=network-online.target
Wants=network-online.target

[Service]
Environment=FOXESS_MODBUS_IP=192.168.0.x
Environment=INFLUXDB_URL=http://your-server:8086
Environment=INFLUXDB_TOKEN=your-token
ExecStart=/usr/local/bin/foxess_feeder
Restart=always
RestartSec=10

[Install]
WantedBy=multi-user.target

Then:

sudo systemctl enable --now foxess-feeder