Inverex Battery Not Charging: Troubleshooting and Fixes

Key Takeaways

• The most likely causes for an Inverex inverter not charging are critically low battery voltage, incorrect charging settings, or a specific fault code.
• Your first step should always be to check the inverter's LCD display for any fault codes (like 03 or 04) and the current battery voltage.
• Never attempt to charge a frozen battery, as this can cause severe damage or explosion.
• Be very cautious when working with metal tools on or around batteries. A potential risk exists to drop a tool, which could spark or short circuit batteries or other electrical parts and cause an explosion.
• Stop DIY troubleshooting and contact a qualified technician if the inverter displays internal component failure codes (01, 05, 06, 08, 09, 51, 52, 53, 55, 57, 58).

Why is my Inverex inverter battery not charging?

Your Inverex inverter, which is a rebadge of the Voltronic Axpert VM III platform, may not be charging its battery due to several common issues. The most frequent causes include critically low battery voltage, incorrect charging settings configured on the inverter, or specific fault codes indicating a problem with the battery or charging circuit. You should begin by checking the inverter's LCD display for any error messages and the current battery voltage reading.

Diagnosis

Follow these steps to diagnose why your Inverex inverter is not charging its battery. Remember that menu and program numbering can differ by model and firmware on rebadged units, so always match settings by name rather than by number.

1. Check the Inverter Display for Fault Codes:

• • Observation: The inverter's LCD screen shows a fault code.
  • Meaning: Refer to the "Error/Fault Code Table" below for the specific meaning and initial fix direction. Fault Code 03 indicates battery voltage is too high, while Fault Code 04 indicates battery voltage is too low.

2. Measure Battery Voltage:

• • Observation: The inverter display shows a very low battery voltage, or the inverter does not power on at all.
  • Meaning: If the battery voltage is too low (e.g., below 1.91V/Cell for startup, or below 1.4V/Cell for no indication), the inverter cannot start or initiate charging. You may need to charge the battery externally or replace it.

3. Verify Charging Settings:

• • Observation: The inverter is on, but no charging current is flowing to the battery, or charging stops prematurely.
  • Meaning: Check Program 02 (Maximum charging current), Program 11 (Maximum utility charging current), Program 16 (Charger source priority), Program 26 (Bulk charging voltage), and Program 27 (Floating charging voltage). Ensure these settings are appropriate for your battery type and system.

4. Inspect Battery Connections:

• • Observation: Loose or corroded battery terminals.
  • Meaning: Poor connections can prevent charging current from reaching the battery or cause voltage drops, leading the inverter to misinterpret battery status. Ensure all terminals are clean and tight. Be very cautious when working with metal tools on or around batteries. A potential risk exists to drop a tool, which could spark or short circuit batteries or other electrical parts and cause an explosion. Always use insulated tools.

5. Check AC Input and PV Input:

• • Observation: No AC input is detected, or PV input is absent/insufficient.
  • Meaning: If your charger source priority (Program 16) relies on AC utility or solar, ensure these inputs are present and within specification. Check AC breakers and PV array connections.

Cause/fix table section

Inverter and Battery Checks for Charging Issues

Troubleshooting battery charging issues with your Inverex inverter involves examining both inverter settings and the physical state of your battery bank.

Inverter-Side Checks: Settings and Configuration

Your Inverex inverter, based on the Axpert VM III platform, offers several programmable settings that directly impact battery charging. Incorrect settings are a common reason for charging problems.

• Charging Current Settings:
• • Program 02: Maximum charging current: This setting controls the total maximum charging current from both solar and utility sources. For a 1.5KW model, the maximum charging current is 60A. For 3KW and 5KW models, options include 70A and 80A. Ensure this is set appropriately for your battery's capacity.
  • Program 11: Maximum utility charging current: This setting specifically limits the charging current drawn from the AC utility. Options range from 2A to 60A, with 30A as the default. For 3KW and 5KW models, options extend to 50A and 60A. If this is set too low, your battery may charge slowly or not fully from the grid.
• Charger Source Priority:
• • Program 16: Charger source priority: This determines whether solar, utility, or both charge your batteries. The default is "Solar and Utility." If set to "Only Solar" and there's insufficient sunlight, your battery will not charge from the grid.
• Battery Type Settings:
• • Program 05: Battery type: This setting is crucial for the inverter to apply the correct charging algorithm. Options include "AGM (default)," "Flooded," and "User-Defined." Selecting the wrong type can lead to undercharging, overcharging, or damage to your batteries.
• Charging Voltages:
• • Program 26: Bulk charging voltage (C.V voltage): This is the voltage at which the battery is charged during the bulk phase. For 24Vdc systems (1.5KW/3KW models), the default is 28.2V. For 48Vdc systems (5KW models), the default is 56.4V. The setting range for 24Vdc models is 25.0V to 31.5V, and for 48Vdc models, it is 48.0V to 61.0V, with an increment of 0.1V.
  • Program 27: Floating charging voltage: This is the voltage maintained once the battery is fully charged to keep it topped off. For 24Vdc systems, the default is 27.0V. For 48Vdc systems, the default is 54.0V. The setting range for 24Vdc models is 25.0V to 31.5V, and for 48Vdc models, it is 48.0V to 61.0V, with an increment of 0.1V.

Important: The default voltages for Programs 26, 27, and 31 are optimized for lead-acid batteries (AGM/Flooded). If using lithium batteries, these default settings are likely incorrect and could damage your battery. Always consult your lithium battery manufacturer's specifications for the correct charging voltages and use the 'User-Defined' option in Program 05, or ensure your BMS is communicating with the inverter to manage these settings automatically.

• Equalization Settings (for Flooded Batteries):
• • If you have flooded lead-acid batteries and have selected "Flooded" or "User-Defined" in Program 05, you may need to check equalization settings.
  • Program 30: Battery equalization: This feature is disabled by default. If enabled, it applies a higher voltage to balance cell voltages.
  • Program 31: Battery equalization voltage: The default is 29.2V for 24Vdc systems and 58.4V for 48Vdc systems.
  • Program 33: Battery equalized time: Default is 60 minutes, with a range of 5 to 900 minutes.
  • Program 35: Equalization interval: Default is 30 days, with a range of 0 to 90 days.
  • Safety Note: Equalization drives the cell into the hydrogen gassing region. Ensure the battery area is well-ventilated and free of sparks or flames if performing equalization.

Battery-Side Checks: Physical Condition and Connections

Beyond inverter settings, the battery itself can be the source of charging problems.

• Physical Connections: Ensure all battery cables are securely connected to the inverter and to each other. Loose connections can cause resistance, heat, and prevent proper charging. Be very cautious when working with metal tools on or around batteries. A potential risk exists to drop a tool, which could spark or short circuit batteries or other electrical parts and cause an explosion. Always use insulated tools.
• Battery Voltage Measurement: Use a multimeter to measure the voltage directly across your battery terminals. Compare this reading to what the inverter displays. A significant difference might indicate a wiring issue or a faulty inverter sensor.
• Battery Health:
• • Critically Low Voltage: If the battery voltage is below 1.91V/Cell, the inverter may not start. If it's below 1.4V/Cell, the inverter may show no response at all. In these cases, the battery may be deeply discharged and require external charging or replacement.
  • Frozen Battery: Never attempt to charge a frozen battery. This can cause the battery to burst, leading to personal injury and damage.

Dead Battery vs. Wrong Settings

It is important to distinguish between a truly dead battery and one that isn't charging due to incorrect inverter settings.

• Dead Battery: A battery that is deeply discharged (below 1.4V/Cell) may not be recognized or charged by the inverter. It might also be physically damaged or at the end of its lifespan. If the inverter shows Fault Code 04, it indicates the battery voltage is too low.
• Wrong Settings: If the battery voltage is within a reasonable range, but charging is not occurring or is inefficient, the issue is likely with the inverter's settings. Review Program 02, 11, 16, 26, and 27 as detailed above. For lithium batteries, the manual indicates "BMS Communication port: CAN and RS232 or RS485" which implies closed-loop communication would govern settings, but specific values are not detailed in the manual.

Safety

Working with batteries and inverters involves significant electrical hazards. Always prioritize safety.

• Qualified Personnel: Only qualified personnel should install or service this device with batteries.
• Battery Type: Charge only deep-cycle lead-acid type rechargeable batteries. Other types of batteries may burst, causing personal injury and damage.
• Frozen Batteries: NEVER charge a frozen battery.
• Metal Tools: Be very cautious when working with metal tools on or around batteries. A potential risk exists to drop a tool, which could spark or short circuit batteries or other electrical parts and cause an explosion. Always use insulated tools.
• DC Over-current Protection: For safety operation and regulation compliance, install a separate DC over-current protector or disconnect device between the battery and inverter. When installing, be very cautious when working with metal tools on or around batteries, as dropping a tool could spark or short circuit batteries or other electrical parts and cause an explosion.
• AC Breaker: Install a separate AC breaker between the inverter and the AC input power source. Recommended specifications are 16A for 1.5KW, 32A for 3KW, and 50A for 5KW models.
• AC/DC Short Circuit: NEVER cause AC output and DC input to short circuit. Do NOT connect to the mains when DC input short circuits.

When to call a technician instead

While many charging issues can be resolved with basic troubleshooting, some problems require professional intervention. You should call a qualified technician if:

• The inverter displays internal component failure codes such as Fault Code 01 (Fan is locked), 05 (Output short circuited or over temperature), 06 (Output voltage too high), 08 (Bus voltage too high), 09 (Bus soft start failed), 51 (Over current or surge), 52 (Bus voltage too low), 53 (Inverter soft start failed), 55 (Over DC voltage in AC output), 57 (Current sensor failed), or 58 (Output voltage too low). These indicate issues beyond user-level repair.
• The battery voltage is critically low (below 1.4V/Cell) and cannot be recovered with an external charger.
• You have checked all settings and connections, but the inverter still fails to charge the battery, and you cannot identify the root cause.
• You are uncomfortable or unsure about performing any of the diagnostic steps, especially those involving electrical measurements.
• The issue persists after following all troubleshooting steps.