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LG Energy Solution•RESU 16H Prime

Analysis by Marcus & Team

LG RESU 16H Prime: Slow Charging on Cloudy Days

Troubleshoot slow charging issues with your LG RESU 16H Prime on cloudy days. Diagnose potential causes & solutions for optimal performance. Residential ESS focus.

Frequently Asked Questions

•What is the expected DC voltage and current output of my PV array on a sunny day?

Refer to the PV system's specifications and the inverter's manual for the expected voltage and current. Use a multimeter and clamp meter to verify.

•How do I check the State of Health (SOH) of my LG RESU 16H Prime battery?

The SOH is typically displayed in the monitoring app or the inverter's diagnostic menu. Refer to the inverter's manual for instructions.

•What is the recommended charging voltage and current for my LG RESU 16H Prime battery?

Refer to the LG RESU 16H Prime installation manual or the inverter's configuration settings for the recommended charging voltage and current parameters.

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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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Common Causes:

Insufficient solar irradiance due to heavy cloud cover reduces the PV array's DC power output.
Incorrect inverter settings: The inverter may be programmed with suboptimal charging parameters for the LG RESU 16H Prime (e.g., lower charging voltage or current limits).
Battery degradation: Over time, the battery's internal resistance increases and its capacity decreases, leading to reduced charging efficiency (lower SOH).
DC disconnect issues: Loose connections or corrosion at the DC disconnect can increase resistance and reduce current flow.
Temperature effects: Low ambient temperatures can reduce the battery's charge acceptance rate.
BMS Fault: A faulty BMS can mismanage charging parameters and falsely report the SOC preventing a full charge cycle.

How It Works:

The LG RESU 16H Prime is a 16 kWh lithium-ion battery system. During charging, the DC power from the PV array is converted to a charging current and voltage suitable for the battery via a hybrid inverter. The Battery Management System (BMS) monitors cell voltages, temperature, and current. If the PV input is insufficient (low irradiance), the charging current to the battery is reduced, resulting in slower charging or incomplete charging if energy consumption exceeds energy generation.

Expert Tip:

Access the LG RESU 16H Prime's advanced diagnostic menu through the installer portal (if available) to view detailed cell voltage data and temperature readings. This can help identify individual cell imbalances or thermal management issues that are contributing to the charging problem.

Important Warnings:

Working with battery storage systems involves high DC voltages. Always disconnect the DC power at the DC disconnect switch before performing any maintenance or troubleshooting. Ensure the PV rapid shutdown system is activated (NEC 690.12). Only qualified electricians should perform work on these systems to avoid electric shock or arc flash hazards.

Recommended Action:

1

Check the PV array output voltage and current using a multimeter and clamp meter, respectively, during peak solar hours, even on cloudy days. Compare to expected output based on the PV system specifications.
2

Verify the inverter's charging settings for the LG RESU 16H Prime. Confirm voltage and current limits are within the manufacturer's recommended range. Use the inverter's user interface or commissioning software.
3

Check the battery's State of Health (SOH) via the monitoring app or the inverter's diagnostic menu. A significantly reduced SOH indicates battery degradation.
4

Inspect the DC disconnect switch and wiring connections between the PV array, inverter, and battery for corrosion, loose connections, or damage. Measure the voltage drop across the disconnect under load; excessive voltage drop indicates high resistance. (NEC 690.13).
5

Monitor the battery temperature. If consistently low, consider thermal insulation to maintain optimal charging temperature.
6

Review historical data from the monitoring app to identify patterns in charging behavior and correlate with weather conditions. Note any error codes or alerts.
7

If a BMS fault is suspected, contact LG Energy Solution support for troubleshooting and possible replacement.

What to Look For:

The LG RESU 16H Prime battery energy storage system (ESS) does not reach its full state of charge (SOC) of 100% on days with low solar irradiance (cloudy days) when integrated with a photovoltaic (PV) system.

Maintenance Tips:

Schedule annual inspections of the PV and battery system, including checking wiring connections, monitoring performance data, and testing battery capacity.
Keep the PV array clean to maximize energy production.
Perform regular firmware updates for the inverter and BMS to ensure optimal performance and address any known issues.
Monitor the battery's State of Health (SOH) and replace the battery when it reaches its end-of-life.