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Fault code reference · Dyness Tower HV & BX51100 battery

Dyness Battery Alarm Reference

Every Dyness battery fault code and BMS alarm across the Tower HV and BX51100 LV range — what triggered it, the most likely cause, and whether you need an engineer. Dyness batteries report faults through the paired inverter, so check your inverter's event log first.

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Sourced from official Dyness Tower and BX51100 manuals Covers both high-voltage Tower and 48V BX rack-mount series Faults report through paired inverter monitoring platform

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BMS protection Startup / power Communication Tower module Capacity
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How to find your fault code. Dyness batteries are battery-only units and do not have a standalone monitoring portal. Alarms and faults surface through the paired inverter's event log — check your inverter manufacturer's portal or display for BMS-related warnings. On the BX51100, the front-panel ALM LED lights red when a protection alarm is active. On the Tower HV, faults are indicated by the BDU status and reported via the inverter's monitoring platform.
BMS protection alarms

Battery Management System protection alarms triggered by current, voltage, or temperature conditions exceeding safe thresholds. These are the most common Dyness alarms and apply to both Tower HV and BX51100 LV series.

Charge overcurrent BMS alarm — Tower HV & BX51100
The BMS has detected a charging current exceeding the battery's rated limit. On the BX51100 the ALM LED turns red and the buzzer sounds. Common causes include incorrect inverter charge current settings (BX51100 max charge is typically 50A at 48V) or a sudden high-power solar surge. Reduce the inverter's battery charge current limit and check that inverter firmware matches the Dyness protocol version.
Discharge overcurrent BMS alarm — Tower HV & BX51100
Discharge current has exceeded the battery's rated maximum. On the BX51100, the ALM LED turns red and the buzzer sounds. This typically occurs when household demand spikes above the battery's continuous discharge rating — for example, a kettle, oven, and immersion heater running simultaneously on backup power. Reduce the load and check the inverter's max discharge current setting matches the Dyness specification.
Cell overvoltage BMS alarm — individual cell exceeded limit
One or more individual cells have exceeded their maximum voltage threshold during charging. The BMS cuts off the charge path to protect the cells. Common causes include inverter charge voltage set too high (BX51100 max absorption is 56V for a 16-cell unit) or a cell balancing problem where weaker cells have lower capacity and stronger cells overcharge. If it recurs after correcting inverter settings, the battery requires professional cell-level diagnosis. Tower HV faults guide →
Cell undervoltage BMS alarm — cell below minimum
One or more cells have dropped below the minimum safe voltage during discharge. On the BX51100, the ALM LED turns red and the buzzer sounds. The BMS disconnects the discharge path to prevent permanent cell damage. Check the inverter's battery shutdown voltage is set correctly (BX51100 recommended shutdown is 48–50V). If the battery was left discharged for an extended period, cells may have self-discharged unevenly and require professional recovery charging.
Total voltage undervoltage BMS alarm — pack voltage below threshold
The total pack voltage has fallen below the BMS low-voltage cut-off. On the BX51100, if pack voltage drops below 35V the front panel indicators will not respond at all — the battery is too deeply discharged for the BMS to power on. Connect the battery to a charging source and allow it to recover. If the pack voltage remains below the BMS wake threshold after several hours of charging, the cells may be damaged and the unit requires professional assessment.
Charge high temperature BMS alarm — temperature protection during charge
The BMS temperature sensor has detected the cell or pack temperature exceeding its safe charging threshold. On the BX51100 the ALM LED turns red. Check that the battery has adequate ventilation — do not install in direct sunlight, sealed cupboards, or near heat sources. The alarm should clear once the temperature drops back within range. If it triggers repeatedly in reasonable ambient conditions, one or more internal temperature sensors or cells may be faulty.
Discharge high temperature BMS alarm — temperature protection during discharge
Cell or pack temperature exceeded the safe threshold during discharge. The BMS reduces or stops discharge to protect the cells. Same ventilation checks apply — ensure adequate clearance and airflow around the battery enclosure. On Tower HV stacked systems, ensure no module is sandwiched in an enclosed space without air circulation above and below each unit.
HV insulation fault ⚠ Safety alarm — Tower HV only
The inverter has detected degraded isolation resistance between the Tower HV battery's DC bus and earth. Do not touch any DC cabling. Common causes include moisture at inter-module connectors or a damaged cable between the BDU and inverter. An engineer can test each module's isolation resistance individually with a megohmmeter. Persistent insulation faults are a safety concern and should not be ignored. Tower HV faults guide →
Startup & power faults

Faults that prevent the battery from powering on, producing DC output, or maintaining its connection to the inverter. These cover both the Tower HV's BDU (Battery Distribution Unit) and the BX51100's front-panel switching.

No indicators — unit unresponsive Tower HV — all lights off
The Tower battery shows no LED activity and does not respond to the POWER WAKE button. Check the BDU DC breaker is in the ON position. Verify the POWER ON toggle switch is engaged. Confirm all inter-module cables are seated — the BDU will not power on if a module connector is loose. If the battery was stored without charge for an extended period, cells may have self-discharged below the BMS wake threshold and require professional recovery.
No indicators — BX51100 unresponsive BX51100 LV — front panel dark
The BX51100 shows no LEDs on the front panel. If the total pack voltage has dropped below 35V, the internal BMS cannot power on. Check the front panel switch (SW) is in the ON position. Verify the DC breaker or fuse on the external DC disconnect (if fitted) has not tripped. Connect the battery to a charging source — if the BMS wakes up after initial charging begins, the battery was over-discharged. If it remains unresponsive, the BMS board may be faulty.
LEDs on but no DC output Tower HV — BDU relay not closing
The Tower modules show LED activity but the inverter reports no battery voltage. The BDU's internal relay has not closed. Press the POWER WAKE button on the BDU to trigger a relay close attempt. If the relay clicks but voltage does not appear at the inverter, check DC cabling between the BDU output and the inverter's battery input. If the relay does not click at all, the BDU relay or control board may be faulty and requires replacement.
No DC output — BX51100 BX51100 LV — SOC LEDs on, no output
The BX51100 front panel shows SOC LEDs but the inverter reports no battery voltage. The battery may have entered an over-discharge protection state. If the SOC LEDs show zero or one segment, the battery has discharged beyond its cut-off and the BMS has opened the discharge path. Connect a charging source to begin recovery. If SOC shows adequate charge but output is absent, the internal contactor or fuse may have failed — contact an engineer.
DC breaker tripped ⚠ Tower HV — BDU breaker open
The BDU's DC breaker has tripped open, disconnecting the battery stack from the inverter. This is typically caused by a short circuit or overcurrent event on the DC cabling between the BDU and inverter. Do not reset the breaker without first inspecting all DC connections for damage, exposed conductors, or incorrect polarity. If the breaker trips again immediately after resetting, a short circuit exists in the DC path and requires professional diagnosis.
Sparks on connection — ALM red BX51100 LV — short circuit at terminals
Sparking was observed when connecting the DC cables and the ALM LED is now solid red. This indicates a short circuit between the positive and negative battery terminals — typically caused by a cable touching the wrong terminal or a tool bridging the connections. Disconnect all cables immediately and inspect the terminals and cable lugs for damage. The BMS may have entered a protective lockout state requiring a full power cycle to reset. If the ALM LED remains red after clearing the short and power cycling, the BMS or internal fuse may be damaged.
Communication faults

Faults related to CAN bus communication between the Dyness battery and the paired inverter, or between multiple batteries in a parallel/stacked configuration. These are among the most common Dyness issues and often stem from DIP switch settings, cable faults, or firmware mismatches.

BMS communication error Inverter event log — no BMS data
The inverter cannot communicate with the Dyness battery over CAN bus. On the BX51100, check the CAN IN/OUT connections on the rear panel — CAN IN connects to the inverter, CAN OUT daisy-chains to the next battery. Verify the CAN cable is not damaged and the RJ45 connectors are fully seated. On the Tower HV, check the communication cable between the BDU and inverter. If cabling is intact, confirm the inverter's battery protocol setting matches the Dyness model. Tower HV faults guide →
Wrong battery model selected Inverter config — protocol mismatch
The inverter's battery type or protocol setting does not match the connected Dyness model. Dyness Tower HV and BX51100 use different CAN protocols. Check your inverter's battery configuration page and select the correct Dyness model from the dropdown. If the exact model is not listed, check the Dyness compatibility matrix for the recommended protocol selection. After changing the setting, restart both the inverter and battery to re-establish communication.
DIP switch addressing fault BX51100 LV — multi-battery addressing
In multi-battery BX51100 installations, each unit requires a unique address set via the DIP switches on the front panel. The first battery (master) should have DIP ON switches set to address 0 (all OFF). Each subsequent slave battery increments the address by one. Duplicate addresses cause communication collisions — the inverter sees intermittent BMS data or fails to detect one or more batteries. Power off all batteries, verify each has a unique DIP address, then power on the master first followed by slaves in order.
Module address conflict Tower HV — duplicate module address
Two or more Tower HV modules in the stack have been assigned the same address. The BDU cannot differentiate between modules and reports a conflict to the inverter. Each 96V module in the stack must have a unique address set during commissioning. Power down the entire stack, verify module addressing via the BDU's configuration interface, reassign any duplicates, then power back on in sequence. Tower HV faults guide →
Firmware version mismatch Multi-battery — inconsistent firmware
In multi-battery setups, all Dyness units must run the same BMS firmware version. A mismatch causes intermittent communication drops or charge/discharge imbalances between units. Check with your installer or Dyness support to confirm all batteries are on the same firmware version. Firmware updates for Dyness batteries typically require a direct USB or CAN connection from a laptop running the Dyness service tool — this is an engineer-level task.
Tower module errors

Error codes specific to the Dyness Tower HV modular battery system. These codes relate to individual module hardware, the LMU (Local Management Unit) within each module, and inter-module communication within the stack.

Error 01 — Temperature sensor Tower module — NTC sensor fault
An internal temperature sensor (NTC) within a Tower module has failed or is reading out of range. The BMS cannot accurately monitor cell temperature in that module, which disables temperature-based charging protection. The affected module needs professional inspection — the NTC thermistor or its wiring harness may need replacing.
Error 05 — MOSFET fault Tower module — switching component
A MOSFET switching component within the module's BMS has failed. MOSFETs control the charge and discharge paths — a failed MOSFET can either lock the module in a permanently connected or permanently disconnected state. This is a hardware fault requiring professional repair. Do not attempt to bypass the affected module in the stack without guidance from a qualified engineer.
Error 06 — Circuit breaker Tower module — internal breaker tripped
The internal circuit breaker within a Tower module has tripped, disconnecting that module from the stack. This is a protective response to an overcurrent or short circuit within the module. Power down the entire stack before inspecting the affected module. If the breaker can be manually reset and holds, the trip may have been transient. If it trips again immediately, the module has an internal fault and must be professionally assessed.
Error 07 — DIP switch Tower module — configuration error
The DIP switch configuration on the affected Tower module does not match the expected setting for its position in the stack. Each module's DIP switch must be set according to Dyness commissioning documentation to define its role (master or slave) and address. Power down the stack, correct the DIP switch setting on the affected module, and power back on.
Error 08 — LMU disconnect slave Tower module — slave module lost
The Local Management Unit (LMU) in the master module has lost communication with a slave module in the stack. Check the inter-module communication cables between each unit in the stack — reseat all connectors. If the issue persists with a specific module, that module's LMU board may be faulty. Try swapping the module's position in the stack to confirm whether the fault follows the module or stays at the position.
Error 09 — Serial number missing Tower module — SN not detected
The BDU cannot read the serial number from one of the Tower modules. This prevents the system from identifying and addressing that module correctly. The serial number is stored in the module's LMU firmware — a corrupted firmware flash or a faulty EEPROM chip is the usual cause. The module requires a firmware reflash using the Dyness service tool, which is an engineer-level procedure.
Error 10 — LMU disconnect master Tower module — master LMU lost
The BDU has lost communication with the master module's LMU. This is more critical than a slave disconnect as the master module coordinates the entire stack. Check the communication cable between the BDU and the master (top) module. Power cycle the entire stack — BDU off, wait 60 seconds, then back on. If the master LMU remains unresponsive, it requires professional replacement.
Error 11 — Software version inconsistent Tower module — firmware mismatch in stack
The LMU firmware versions across the Tower modules in the stack do not match. All modules must run identical firmware to coordinate charge balancing and protection correctly. This commonly occurs when a replacement module with a different firmware version is added to an existing stack. Contact Dyness support or a qualified engineer to update all modules to the same firmware version using the service tool.
Error 12 — Multi master Tower module — multiple masters detected
More than one module in the Tower stack is configured as the master. Only one module should be set as master — typically the top module in the stack. Power down the entire stack and check the DIP switch or address configuration on each module to ensure only one is designated as master. Correct any duplicates, then power on the master module first followed by slave modules in sequence.
Capacity & performance

Issues related to reduced runtime, incomplete charging, or unexpected capacity loss. These are not always triggered by a specific alarm code but are commonly reported alongside BMS warnings in the inverter's event log.

Short runtime — low usable capacity BX51100 / Tower — performance degradation
The battery reaches its low SOC cut-off faster than expected. On the BX51100, if the battery's capacity has degraded over time, the usable energy between the fully charged state and the low-voltage cut-off will decrease. Check the inverter's battery discharge data — if the delivered kWh per cycle has dropped significantly from the nameplate rating, the cells have lost capacity. Lithium iron phosphate cells degrade gradually but deep-discharge events or prolonged storage at zero SOC accelerate degradation. A professional capacity test can quantify the remaining usable capacity.
Cannot charge to 100% SOC BX51100 / Tower — incomplete charging
The battery SOC stops climbing before reaching 100%, or the inverter reports fully charged at a lower-than-expected voltage. On the BX51100, check the inverter's charge voltage settings — absorption voltage should be 56V and float voltage 55.5V for a standard 16-cell unit. If settings are correct but the battery still won't reach full charge, one or more cells may have reduced capacity and are reaching their individual overvoltage limit before the pack reaches full voltage. This causes the BMS to cut off charging prematurely to protect the weak cell.
Cell imbalance warning Tower HV — voltage spread between cells
The BMS has detected an abnormal voltage difference between individual cells or modules in the Tower stack. A small amount of cell imbalance is normal and corrected by the BMS passive balancing circuit during charging. If the imbalance exceeds the BMS threshold (typically 100mV between cells), the system flags a warning. Persistent imbalance may indicate a failing cell, a faulty module, or a module that has been replaced without proper commissioning. Professional cell-level voltage testing identifies the affected module. Tower HV faults guide →
Alarm not listed here?

Dyness battery faults appear through your paired inverter's monitoring, and the exact wording varies by inverter brand and firmware version. If you're seeing a BMS-related warning that isn't covered above, share the exact text from your inverter's event log and we'll identify it. Dyness also provide support via their UK distributor.

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Full diagnostic guides by fault type
HV insulation · BMS comm · cell imbalance
Tower-Pro HV fault diagnosis

Full diagnostic guide — insulation testing, module addressing, cell voltage checks, BDU relay, and stack commissioning.
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Browse all Dyness battery problems with step-by-step diagnostic guides and solutions.
Manuals · datasheets · wiring
Dyness documents

Official Dyness manuals, datasheets, and wiring diagrams for Tower HV and BX51100 series.

Dyness battery fault questions

Dyness batteries are battery-only units and do not have their own monitoring portal. Faults and alarms surface through your paired inverter's event log — for example, if your Tower is connected to a GivEnergy inverter, check givenergy.cloud for BMS communication errors and battery warnings. On the BX51100, the front-panel ALM LED lights red when a protection alarm is active, and the SOC LEDs show remaining charge. Check your inverter's monitoring for the specific alarm text.

The BX51100 front panel has several indicator LEDs. The RUN LED flashes green during normal operation and stays solid green when fully charged. The ALM LED lights red when a protection alarm is active — overcurrent, overvoltage, undervoltage, or temperature. The SOC LEDs (four segments) show remaining charge level. The COM LED indicates CAN bus communication status with the paired inverter. If ALM is red, check the inverter's event log for the specific fault before taking any action.

On the Tower HV, switch the POWER ON toggle off, wait 60 seconds, then switch it back on. On the BX51100, toggle the front panel SW switch off and back on after 30 seconds. Many protection alarms — such as temporary over-temperature or transient overcurrent during a high-demand spike — clear automatically once the triggering condition resolves. If the same alarm returns after a power cycle, the fault is persistent and needs professional diagnosis.

STS offers remote diagnostic assessments from £75. Because Dyness batteries report through the paired inverter, our engineers review your inverter portal data remotely to identify BMS alarms, communication faults, and performance issues. The diagnostic pinpoints the root cause and recommends whether the issue can be resolved with a settings change, firmware update, or requires an on-site visit — saving you the cost of an unnecessary callout.

Insulation faults reported by the inverter when a Dyness Tower HV is connected usually indicate degraded isolation resistance between the battery's high-voltage DC bus and earth. On modular Tower systems, moisture at inter-module connectors or a damaged cable between the BDU and inverter is the most common cause. An engineer can test each module's isolation resistance individually with a megohmmeter. Do not ignore persistent insulation faults — they indicate a potential safety issue.

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