The gateway connects but soc and voltage always read zero. Why?

Verify the Modbus unit ID in the portal matches the EMS address set on the BMS (register 4131). A mismatch causes the BMS to ignore all requests silently. Also confirm the firmware date is 20191016 or later, as earlier firmware does not expose these registers.

I see Master_Slave_Comm_Fault on the BMS. What causes this?

This fault appears when battery rack addresses are set incorrectly or when the RS485 cable between the master and slave batteries is broken or not fully seated. Check that master address is 0, and slave rack addresses are 1, 2, 3, and so on sequentially. Restart the system after correcting addresses.

Values look correct but then go stale or disappear periodically. What now?

The ems_communication_timeout register (4130) defines how long the BMS waits for a poll before entering a timeout state. If the ModbusCloud Gateway poll interval exceeds this timeout, the BMS may suspend responses. Increase the timeout value via register 4130 or reduce the gateway poll interval.

Is it safe to write to the cluster start/stop or rack usage registers remotely?

Use write registers with caution. Writing to cluster_start_stop_a (4119) or any rack_X_usage_a register can interrupt active charge or discharge cycles and may trip BMS protection limits. Always confirm the system is in a safe idle state before issuing write commands, and consult the Soltaro installation documentation before using the reset register (4100) in production.

Free Modbus template: Bms Soltaro Cluster VersionB

The Soltaro Soltaro Cluster VersionB is a lithium iron phosphate (LFP) battery management system designed for multi-rack residential and light-commercial energy storage. It communicates via Modbus RTU over RS485 and requires firmware dated 20191016 or later. This template reads cluster state of charge, DC voltage, current, charge indication, system running state, insulation status, and BMS charge/discharge power limits. It also exposes write registers for cluster start/stop, per-rack enable/disable, insulation alarm thresholds, and EMS address configuration. Use it to keep a complete view of a multi-rack Soltaro cluster from your ModbusCloud portal.

Registers (29)

18 read / 11 write

Name	Address	Function	Type	Unit	Access
reset Write to trigger a system reset command.	4100	FC16	uint16		W
cluster_start_stop_a Write to start or stop the battery cluster.	4119	FC16	uint16		W
rack_1_usage_a Write to enable or disable rack 1 in the cluster.	4120	FC16	uint16		W
rack_2_usage_a Write to enable or disable rack 2 in the cluster.	4121	FC16	uint16		W
rack_3_usage_a Write to enable or disable rack 3 in the cluster.	4122	FC16	uint16		W
rack_4_usage_a Write to enable or disable rack 4 in the cluster.	4123	FC16	uint16		W
rack_5_usage_a Write to enable or disable rack 5 in the cluster.	4124	FC16	uint16		W
cluster_start_stop_b Current start/stop state of the battery cluster.	4119	FC03	uint16		R
rack_1_usage_b Current enabled/disabled state of rack 1.	4120	FC03	uint16		R
rack_2_usage_b Current enabled/disabled state of rack 2.	4121	FC03	uint16		R
rack_3_usage_b Current enabled/disabled state of rack 3.	4122	FC03	uint16		R
rack_4_usage_b Current enabled/disabled state of rack 4.	4123	FC03	uint16		R
rack_5_usage_b Current enabled/disabled state of rack 5.	4124	FC03	uint16		R
system_insulation_level_1_a Write the primary insulation resistance alarm threshold.	4127	FC16	uint16		W
system_insulation_level_2_a Write the secondary insulation resistance alarm threshold.	4128	FC16	uint16		W
ems_communication_timeout_a Write the EMS communication timeout value.	4130	FC16	uint16		W
ems_address_a Write the Modbus slave address for the EMS interface.	4131	FC16	uint16		W
system_insulation_level_1_b Read the active primary insulation resistance alarm threshold.	4127	FC03	uint16		R
system_insulation_level_2_b Read the active secondary insulation resistance alarm threshold.	4128	FC03	uint16		R
ems_communication_timeout_b Read the configured EMS communication timeout value.	4130	FC03	uint16		R
ems_address_b Read the configured Modbus EMS slave address.	4131	FC03	uint16		R
charge_indication Indicates whether the system is currently charging.	4164	FC03	uint16		R
current Total cluster DC current, amperes.	4165	FC03	uint16	A	R
soc Battery cluster state of charge, 0 to 100 percent.	4167	FC03	uint16	%	R
system_running_state Operational state of the battery cluster system.	4168	FC03	uint16		R
voltage Total cluster DC bus voltage, volts.	4169	FC03	uint16	V	R
system_insulation Measured insulation resistance of the battery system.	4170	FC03	uint16		R
bp_charge_bms BMS-reported maximum allowed charge power limit.	4174	FC03	uint16		R
bp_discharge_bms BMS-reported maximum allowed discharge power limit.	4175	FC03	uint16		R