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SolarEdge•SolarEdge Home

Analysis by Marcus & Team

SolarEdge Home: Resolving the "BMS Lost" Error

Troubleshooting the SolarEdge Home "BMS Lost" error. Diagnose communication issues, safety protocols, and battery system failures. Expert solutions for residential systems.

Frequently Asked Questions

•What are the common causes of communication loss between the inverter and the battery BMS?

Common causes include faulty cabling, outdated firmware, BMS failures, and system errors requiring qualified electrician intervention.

•How can I safely check the DC voltage on a SolarEdge battery system?

Safely checking DC voltage requires qualified electrician with proper PPE and disconnecting the PV array and battery using the DC disconnect switches before any measurements. Refer to NEC 690.

•What are the risks of ignoring a "BMS Lost" error?

Ignoring the "BMS Lost" error can lead to battery damage, reduced system performance, and potentially unsafe operating conditions, requiring immediate qualified electrician support.

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Marcus leads the technical research department at Storage Faults. Together with a team of systems analysts, he specializes in translating complex solar storage error codes into actionable diagnostic steps for the US market.

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Critical Safety Precautions:

SolarEdge systems operate at high DC voltages (up to 600V+). Contact with these voltages can be lethal. Always disconnect the PV array and battery system using the appropriate DC disconnect switches before performing any maintenance or troubleshooting. Wear appropriate personal protective equipment (PPE), including insulated gloves and safety glasses. Work must be performed by a qualified electrician familiar with NEC 690 and local electrical codes. Arc flash hazards are present; maintain safe working distances and never work on live circuits. Verify rapid shutdown operation.

Solution:

1

*Safety First**: Ensure the PV array is disconnected using the DC disconnect switch. Verify rapid shutdown is active per NEC 2017/2020 requirements. This should de-energize the DC conductors. Do NOT work on live circuits.
2

*Visual inspection**: Inspect the communication cable between the inverter and the battery for any visible damage. Use a multimeter to check the cable for continuity. Replace if damaged. Note cable shielding for noise immunity.
3

*Check DC Disconnect**: Confirm the DC disconnect switch for the battery is closed (ON). Verify DC voltage to the battery using a calibrated multimeter.
4

*Firmware Update**: Using the SolarEdge monitoring portal or app (with appropriate installer access), check for and install any available firmware updates for the inverter and battery. Incorrect or interrupted firmware updates can cause significant issues.
5

*BMS Reset (If Applicable)**: Some battery systems have a reset procedure for the BMS. Consult the battery manufacturer's documentation for specific instructions. This usually involves a specific sequence of disconnects and reconnects.
6

*Voltage and Current Measurement**: After confirming all connections, use a calibrated clamp meter to measure the DC current flowing into and out of the battery during charging and discharging (if possible). Abnormal current readings can indicate a battery or BMS fault.
7

*Contact SolarEdge Support**: If the problem persists after performing the above steps, contact SolarEdge technical support for further assistance. Provide detailed information about the system configuration, error codes, and troubleshooting steps already taken. They may require a qualified electrician to perform more invasive testing.

Technical Background:

The SolarEdge Home Hub inverter utilizes a DC-coupled architecture, where PV energy is first converted to DC voltage and then used to charge the battery or inverted to AC for grid export or home consumption. The BMS is a critical component responsible for monitoring and controlling battery voltage, current, temperature, and state of charge (SOC). It communicates with the inverter to ensure safe and optimal battery operation, including over-voltage, over-current, over-temperature, and under-voltage protection. The BMS also manages cell balancing and prevents over-discharge. Loss of communication disables safety features.

Pro Tip:

In the SolarEdge commissioning toolkit, check the "Battery Status" page. This page provides real-time data about the battery's voltage, current, temperature, SOC, SOH, and BMS status. Any abnormal readings can help pinpoint the source of the "BMS Lost" error. Also, check the event log for any recent events that might indicate a communication failure.

Common Causes:

Faulty communication cable between the inverter and the battery. Check for loose connections, corrosion, or damage to the cable.
BMS failure: The BMS itself may be defective and unable to communicate.
Inverter firmware issue: An outdated or corrupted inverter firmware may cause communication problems.
Battery system failure: A critical fault within the battery system can cause the BMS to shut down and stop communicating.
DC Disconnect open: The DC disconnect switch for the battery could be open, cutting power to the battery and BMS.
Electrical noise: Excessive electrical noise on the DC bus can interfere with communication between the inverter and BMS.

Symptoms:

The SolarEdge monitoring portal or app displays a "BMS Lost" error, indicating a communication failure between the SolarEdge Home Hub inverter and the battery management system (BMS) of the connected battery. The battery may not charge or discharge, and backup power functionality may be impaired.

Maintenance Tips:

Regularly check the SolarEdge monitoring portal or app for any error messages or warnings.
Schedule periodic maintenance with a qualified electrician to inspect the system and ensure all components are functioning correctly.
Keep the inverter and battery clean and free of dust and debris to prevent overheating.
Ensure the inverter and battery are installed in a well-ventilated area.
Update the inverter and battery firmware regularly to benefit from bug fixes and performance improvements.