Free Modbus template: Pylontech Pylontech

Name: Pylontech Pylontech
Brand: Pylontech
SKU: e7468dc6-7512-46f6-b399-0e8db8fafa9b

Pylontech lithium iron phosphate battery systems are modular residential and commercial energy storage units, widely deployed in solar self-consumption and backup-power installations. This template communicates over Modbus RTU via the RS485 port on the master Pylontech battery. It reads state of charge, state of health, pack voltage and current, system and per-cell temperature, per-cell and per-module voltage extremes, BMS charge and discharge limits, cycle count, daily and lifetime throughput counters, and BMS status flags including charge-forbidden and discharge-forbidden marks. One write register allows remote sleep or wake control. The result is full BMS visibility inside your ModbusCloud portal without any additional converter hardware.

Things to watch for

All register reads return errors. What should I check first?

Confirm the RS485 wiring uses the correct port: the Pylontech RS485 RJ45 connector, not the Link port used for inter-battery communication. Check that the A and B lines are not swapped. Verify baud rate is 9600 and the unit ID in the portal matches the address set on the battery. A missing or wrong termination resistor on longer cable runs can also cause consistent read failures.

The historical accumulated capacity counters occasionally jump by huge amounts. Is this a scaling issue?

This is a known BMS firmware behaviour: the lifetime charge and discharge counters in Pylontech systems can occasionally increment by unrealistic amounts in a single update cycle. The daily counters are similarly affected. Cross-check against the daily registers and treat sudden large jumps as firmware artefacts rather than real throughput. Do not use these counters for billing-grade metering without independent verification.

The charge_forbidden_mark or discharge_forbidden_mark is set. What triggered it?

These flags are set by the BMS when a protection condition is active, such as a cell voltage out of range, over-temperature, or insulation resistance fault. Check the insulation_resistance and insulation_resistance_error_level registers alongside the min and max cell voltage and temperature registers to locate the specific condition. Clearing the fault requires resolving the underlying issue; the BMS will lower the flag automatically once conditions return to normal.

Is it safe to write to the sleep_wake_channel register during normal operation?

Use the sleep_wake_channel write register with caution. Sending a sleep command while the battery is actively charging or discharging can interrupt the inverter control loop and may trigger inverter protection. Only write to this register during planned maintenance windows, confirm with your Pylontech integration documentation what values are valid, and ensure the connected inverter is in a safe state before issuing the command.

Registers (45)

44 read / 1 write

Name	Address	Function	Type	Unit	Access
pylontech_internal_version_number BMS firmware version number reported by the Pylontech system.	4107	FC03	uint16		R
system_number_of_parallel_piles Total number of battery piles connected in parallel.	4108	FC03	uint16	count	R
voltage DC pack voltage of the battery system, volts.	4355	FC03	uint16	V	R
current Pack current; positive indicates charge, negative indicates discharge.	4356	FC03	int32	A	R
system_temperature Overall system temperature reported by the BMS, degrees Celsius.	4358	FC03	int16	°C	R
soc State of charge, 0 to 100 percent.	4359	FC03	uint16	%	R
cycle_times Cumulative charge/discharge cycle count for the battery system.	4360	FC03	uint16	count	R
charge_max_voltage Maximum allowable charge voltage set by the BMS, volts.	4361	FC03	uint16	V	R
bp_charge_bms BMS-reported maximum charge power limit for the battery pack.	4362	FC03	int32	W	R
discharge_min_voltage Minimum allowable discharge cutoff voltage set by the BMS, volts.	4364	FC03	uint16	V	R
bp_discharge_bms BMS-reported maximum discharge power limit for the battery pack.	4365	FC03	int32	W	R
max_cell_voltage Highest individual cell voltage across all cells, millivolts.	4368	FC03	uint16	mV	R
min_cell_voltage Lowest individual cell voltage across all cells, millivolts.	4369	FC03	uint16	mV	R
max_voltage_cell_number Index number of the cell with the highest voltage.	4370	FC03	uint16		R
min_voltage_cell_number Index number of the cell with the lowest voltage.	4371	FC03	uint16		R
max_cell_temperature Highest individual cell temperature across all cells, degrees Celsius.	4372	FC03	int16	°C	R
min_cell_temperature Lowest individual cell temperature across all cells, degrees Celsius.	4373	FC03	int16	°C	R
max_temperature_cell_number Index number of the hottest cell in the pack.	4374	FC03	uint16		R
min_temperature_cell_number Index number of the coolest cell in the pack.	4375	FC03	uint16		R
max_module_voltage Highest voltage among all modules in the system, volts.	4376	FC03	uint16	V	R
min_module_voltage Lowest voltage among all modules in the system, volts.	4377	FC03	uint16	V	R
max_voltage_module_number Index number of the module with the highest voltage.	4378	FC03	uint16		R
min_voltage_module_number Index number of the module with the lowest voltage.	4379	FC03	uint16		R
max_module_temperature Highest temperature among all modules in the system, degrees Celsius.	4380	FC03	int16	°C	R
min_module_temperature Lowest temperature among all modules in the system, degrees Celsius.	4381	FC03	int16	°C	R
max_temperature_module_number Index number of the hottest module in the system.	4382	FC03	uint16		R
min_temperature_module_number Index number of the coolest module in the system.	4383	FC03	uint16		R
soh State of health, 0 to 100 percent, indicates battery degradation.	4384	FC03	uint16	%	R
remaining_capacity Current remaining capacity available in the battery system.	4385	FC03	uint32		R
charge_capacity Total charge capacity of the battery system at present state.	4387	FC03	uint32		R
discharge_capacity Total discharge capacity of the battery system at present state.	4389	FC03	uint32		R
daily_accumulated_charge_capacity Total energy charged into the system since last daily reset.	4391	FC03	uint32		R
daily_accumulated_discharge_capacity Total energy discharged from the system since last daily reset.	4393	FC03	uint32		R
historical_accumulated_charge_capacity Lifetime cumulative charge energy for the battery system.	4395	FC03	uint32		R
historical_accumulated_discharge_capacity Lifetime cumulative discharge energy for the battery system.	4397	FC03	uint32		R
request_force_charge_mark BMS flag requesting the inverter to initiate a force charge cycle.	4399	FC03	uint16		R
request_balance_charge_mark BMS flag requesting the inverter to perform a balancing charge.	4400	FC03	uint16		R
number_of_piles_in_parallel Number of battery piles currently active in the parallel bank.	4401	FC03	uint16	count	R
number_of_modules_in_series_per_pile Count of modules connected in series within each pile.	4406	FC03	uint16	count	R
number_of_cells_in_series_per_pile Count of cells connected in series within each pile.	4407	FC03	uint16	count	R
charge_forbidden_mark BMS flag indicating charging is currently prohibited.	4408	FC03	uint16		R
discharge_forbidden_mark BMS flag indicating discharging is currently prohibited.	4409	FC03	uint16		R
insulation_resistance Measured insulation resistance of the battery system.	4424	FC03	uint16	Ω	R
insulation_resistance_error_level Severity level of any insulation resistance fault detected.	4425	FC03	uint16		R
sleep_wake_channel Write register to trigger sleep or wake of the battery system.	4240	FC16	uint16		W