UN-Vbatt: Battery undervoltage

The "UN-Vbatt" error signals that the battery's voltage has fallen below the inverter's operational threshold.

Why it's problematic

The inverter may shut down to protect the battery from further discharge, interrupting power supply.
Deep discharges can shorten battery lifespan and affect overall system performance.

Possible causes

High energy demand exceeding battery capacity: If the load consumes more power than the battery can supply, the voltage will drop, triggering the error.
Battery disconnect or faulty wiring: A break in the power cables connecting the battery to the inverter will lead to a "no battery" alarm and undervoltage. Loose connections or a faulty isolator within the battery can also cause this issue.
Battery aging or degradation: Over time, battery capacity decreases, making it more susceptible to undervoltage conditions, especially under heavy loads.
Incorrect battery settings or compatibility: Using a battery incompatible with the inverter or having incorrect battery settings programmed in the inverter can cause various issues, including "Battery Name Fail" and undervoltage alarms.

Before you begin

Safety First: Working with electrical equipment always involves risks. Ensure you are qualified and follow appropriate safety precautions. Disconnect the inverter from both AC and DC sources before performing any physical inspection or adjustments.

Gather Information: Before starting troubleshooting, have the inverter manual on hand. You should also gather information about the inverter model and serial number, the installation date, and the PV array configuration (number of panels, capacity, and number of strings).

Troubleshooting steps

Restart the inverter: This can resolve temporary communication glitches.
Check battery voltage readings: Verify the battery voltage reading on the inverter's display. You can access this information in the "Information" screen. Compare the reading to the minimum battery voltage specified in the inverter's manual.
Inspect battery connections: Check for loose or damaged connections between the battery and the inverter. Pay close attention to the battery isolator switch and circuit breaker, ensuring they are properly engaged. Tighten any loose connections and replace damaged cables. You can use a multimeter to check for continuity and voltage.
Verify battery compatibility and settings: Ensure the connected battery is compatible with the inverter and that the correct battery settings are programmed in the inverter. Consult the inverter manual and battery documentation for compatibility information and setting instructions.
Assess energy consumption: Evaluate if the load demand exceeds the battery's capacity. If so, consider reducing energy consumption during peak periods or upgrading the battery system.
Test battery health: If the battery is aged or degraded, it may need to be replaced. Consider a professional battery capacity test to determine its remaining health.

Verifying the solution

After completing the steps, monitor the inverter display and battery voltage. The "Battery Undervoltage" error should disappear if the battery voltage recovers to an acceptable range. The inverter should resume regular operation.

If the problem is not resolved

If the error continues, there might be an internal inverter fault or a more complex battery issue.

As a system owner: Reach out to the inverter installer or distributor for help. You can find installer details in the MyAutarco app.
As a certified installer: Contact Autarco Support through Helios.