All registers return zero or an error. What is wrong?

Modbus TCP is disabled by default on Victron GX devices. Navigate to Settings, then Services on the GX device and confirm Modbus-TCP is enabled. Also verify the unit ID in your portal matches the solar charger's Device Instance, which is listed on the Device list tab in the Modbus-TCP service menu of the GX device.

PV voltage registers 776 and 777 always read zero on multi-tracker units. Why?

On chargers with multiple independent MPPT trackers, the single-channel PV voltage (address 776) and current (address 777) may be unavailable because the device exposes per-tracker values instead. Read pv_voltage_tracker_0 through tracker_3 at addresses 3700 to 3703 for individual string voltages.

The charge_state register shows value 252. What does that mean?

A value of 252 on the charge_state register means the charger is under external control, typically because it is part of a Victron ESS system where the inverter-charger dictates the charge curve. This is normal behaviour in an ESS configuration and does not indicate a fault.

Yield registers show unexpected values after midnight. Is this a scaling issue?

Yield today registers reset at midnight local time on the GX device. Values are stored in kWh as uint16 with a scaling factor of 0.01 applied by the GX Modbus layer, so a raw register value of 350 equals 3.50 kWh. Confirm your polling client applies the correct scaling factor from the Victron CCGX Modbus TCP register list spreadsheet.

Free Modbus template: Victron DC-Charger

Name: Victron DC-Charger
Brand: Victron
SKU: 8c373709-025f-4bbc-9102-abdcb4a9ec80

The Victron DC-Charger is a solar MPPT charge controller that converts PV array power into controlled DC battery charging, used in off-grid, marine, and mobile energy systems. This Modbus TCP template reads battery voltage, current, temperature, and active charge state alongside per-tracker PV voltages, per-tracker daily and yesterday yield, peak power records, alarm flags for low and high battery voltage, equalization status, and the active error code. Installers gain a complete real-time and historical picture of charger behaviour without polling the VRM portal manually.

Registers (40)

40 read / 0 write

Name	Address	Function	Type	Unit	Access
battery_voltage DC battery terminal voltage measured by the charger.	771	FC03	uint16	V	R
battery_current DC charge current into the battery; positive means charging.	772	FC03	int16	A	R
battery_temperature Battery temperature in degrees Celsius, from sensor if fitted.	773	FC03	int16	°C	R
charger_on_off Charger on/off state: 1 = on, 4 = off.	774	FC03	uint16		R
charge_state Active charge stage: 0=off, 2=fault, 3=bulk, 4=absorption, 5=float, 6=storage, 7=equalize.	775	FC03	uint16		R
voltage PV input voltage at the charger terminals.	776	FC03	uint16	V	R
current PV input current at the charger terminals.	777	FC03	uint16	A	R
equalization_pending Equalization pending flag: 0=no, 1=yes, 2=error, 3=unavailable.	778	FC03	uint16		R
equalization_time_remaining Seconds remaining in the active equalization cycle.	779	FC03	uint16	s	R
relay_on_the_charger State of the charger's internal relay: 0=open, 1=closed.	780	FC03	uint16		R
low_battery_voltage_alarm Low battery voltage alarm status: 0=no alarm, 2=alarm.	782	FC03	uint16		R
high_battery_voltage_alarm High battery voltage alarm status: 0=no alarm, 2=alarm.	783	FC03	uint16		R
yield_today Total energy harvested today by the charger, in kWh.	784	FC03	uint16	kWh	R
max_charge_power_today Peak charge power recorded today, in watts.	785	FC03	uint16	W	R
yield_yesterday Total energy harvested yesterday by the charger, in kWh.	786	FC03	uint16	kWh	R
max_charge_power_yesterday Peak charge power recorded yesterday, in watts.	787	FC03	uint16	W	R
error_code Active error code; 0 means no error.	788	FC03	uint16		R
actual_power Instantaneous PV output power delivered to the battery, in watts.	789	FC03	uint16	W	R
actual_energy Cumulative energy delivered in the current session, in watt-hours.	790	FC03	uint16	Wh	R
mpp_operation_mode Current MPPT tracker operating mode enumeration.	791	FC03	uint16		R
pv_voltage_tracker_0 PV string voltage on MPPT tracker channel 0.	3700	FC03	uint16	V	R
pv_voltage_tracker_1 PV string voltage on MPPT tracker channel 1.	3701	FC03	uint16	V	R
pv_voltage_tracker_2 PV string voltage on MPPT tracker channel 2.	3702	FC03	uint16	V	R
pv_voltage_tracker_3 PV string voltage on MPPT tracker channel 3.	3703	FC03	uint16	V	R
yield_today_tracker_0 Energy harvested today by MPPT tracker channel 0.	3708	FC03	uint16	kWh	R
yield_today_tracker_1 Energy harvested today by MPPT tracker channel 1.	3709	FC03	uint16	kWh	R
yield_today_tracker_2 Energy harvested today by MPPT tracker channel 2.	3710	FC03	uint16	kWh	R
yield_today_tracker_3 Energy harvested today by MPPT tracker channel 3.	3711	FC03	uint16	kWh	R
yield_yesterday_tracker_0 Energy harvested yesterday by MPPT tracker channel 0.	3712	FC03	uint16	kWh	R
yield_yesterday_tracker_1 Energy harvested yesterday by MPPT tracker channel 1.	3713	FC03	uint16	kWh	R
yield_yesterday_tracker_2 Energy harvested yesterday by MPPT tracker channel 2.	3714	FC03	uint16	kWh	R
yield_yesterday_tracker_3 Energy harvested yesterday by MPPT tracker channel 3.	3715	FC03	uint16	kWh	R
max_charge_power_today_tracker_0 Peak charge power today on MPPT tracker channel 0, in watts.	3716	FC03	uint16	W	R
max_charge_power_today_tracker_1 Peak charge power today on MPPT tracker channel 1, in watts.	3717	FC03	uint16	W	R
max_charge_power_today_tracker_2 Peak charge power today on MPPT tracker channel 2, in watts.	3718	FC03	uint16	W	R
max_charge_power_today_tracker_3 Peak charge power today on MPPT tracker channel 3, in watts.	3719	FC03	uint16	W	R
max_charge_power_yesterday_tracker_0 Peak charge power yesterday on MPPT tracker channel 0, in watts.	3720	FC03	uint16	W	R
max_charge_power_yesterday_tracker_1 Peak charge power yesterday on MPPT tracker channel 1, in watts.	3721	FC03	uint16	W	R
max_charge_power_yesterday_tracker_2 Peak charge power yesterday on MPPT tracker channel 2, in watts.	3722	FC03	uint16	W	R
max_charge_power_yesterday_tracker_3 Peak charge power yesterday on MPPT tracker channel 3, in watts.	3723	FC03	uint16	W	R