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LG Energy Solution•RESU Prime

Analysis by Marcus & Team

LG RESU Prime Error 90: Troubleshooting Guide

Troubleshoot LG RESU Prime Error 90. Diagnose communication failures, voltage imbalances, and BMS errors. Expert solutions for residential battery systems.

Frequently Asked Questions

•What tools are needed to troubleshoot Error 90?

A multimeter, CAN bus analyzer (optional), insulated tools, and PPE are required.

•Is Error 90 covered under warranty?

Warranty coverage depends on the age of the system and the specific terms of the LG Energy Solution warranty. Check your warranty documentation.

•Can I fix Error 90 myself?

Troubleshooting should be performed by a qualified technician due to high voltage hazards. Contact a certified LG installer for assistance.

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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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Symptoms:

The LG RESU Prime displays Error 90 on the monitoring app or inverter screen. The battery system may cease charging or discharging, and backup power functionality may be unavailable. The inverter may report a communication fault with the battery.

Important Warnings:

The LG RESU Prime operates at high DC voltages (typically 400V DC). Improper handling can result in severe electrical shock, arc flash, or thermal runaway leading to fire. Always disconnect both AC and DC power before performing any maintenance or troubleshooting. Only qualified electricians with experience in battery storage systems should perform repairs. Adhere to all NEC guidelines for rapid shutdown and safety procedures. Wear appropriate personal protective equipment (PPE), including safety glasses, gloves, and insulated tools.

How It Works:

The LG RESU Prime utilizes a Battery Management System (BMS) to monitor cell voltages, temperature, current, and overall health. Error 90 typically indicates a communication failure between the BMS and the inverter or a critical fault within the battery pack itself. The system relies on a CAN bus or similar protocol for data exchange. High DC voltages (typically 400V DC) are present within the battery pack, posing a significant electrical hazard. Internal to the battery, individual lithium-ion cells are connected in series and parallel configurations. The BMS ensures proper cell balancing to maintain optimal performance and prevent overvoltage or undervoltage conditions.

Solution:

1

*Safety First:** Disconnect the AC power to the inverter and then use the DC disconnect switch to isolate the RESU Prime battery from the system. Verify zero DC voltage using a calibrated multimeter.
2

*Visual inspection:** Check all wiring connections between the RESU Prime and the inverter for tightness, corrosion, or damage. Pay close attention to the CAN bus communication cables.
3

*Communication Check:** Use a CAN bus analyzer (if available) to verify communication between the BMS and the inverter. Check for error messages or missing data packets.
4

*Voltage Measurement:** After ensuring the system is de-energized, use a calibrated multimeter to measure the voltage of each battery module within the RESU Prime (if accessible) and compare them to the BMS readings (if obtainable prior to complete failure). Significant discrepancies indicate a potential cell imbalance or BMS fault.
5

*Firmware Update:** Consult the LG Energy Solution documentation for firmware update procedures for both the RESU Prime and the inverter. Ensure compatibility between the two.
6

*licensed technician Diagnosis:** If the error persists, contact a certified LG Energy Solution installer or technician for advanced diagnostics and repair. Do not attempt internal repairs on the battery pack yourself due to high voltage and potential fire hazards.
7

*Warranty Check:** Verify that the system is still under warranty. Contact LG Energy Solution for warranty service if applicable.

Why This Happens:

Disrupted CAN bus communication between the RESU Prime and the inverter.
Internal BMS failure, preventing accurate voltage or temperature readings.
Cell voltage imbalance exceeding the BMS safety threshold.
Damaged or loose wiring connections within the battery pack or between the battery and inverter.
Firmware incompatibility or corruption in either the BMS or the inverter.
Environmental factors like extreme temperatures exceeding the battery's operating range.

Technical Recommendation:

Some LG RESU Prime systems have a hidden diagnostic menu accessible through a specific key combination on the inverter or monitoring app. Consult the installer manual or contact LG Energy Solution support to obtain the access code. This menu often provides detailed error logs and system parameters that can aid in diagnosing the root cause of Error 90.

Preventative Care:

Regularly inspect wiring connections for tightness and corrosion.
Ensure proper ventilation around the RESU Prime to prevent overheating.
Follow the manufacturer's recommendations for firmware updates.
Schedule annual system inspections by a qualified technician to check battery health and performance.
Monitor the system's performance via the monitoring app for any signs of degradation or anomalies.