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+263 78 922 2847Learn to decode MUST inverter error codes, troubleshoot battery and power issues, and restore your solar system efficiently.
Most inverter errors are related to the battery, making proper battery maintenance and monitoring crucial for reliable solar system performance. On MUST inverters, some of the most common battery-related issues include Error 04: Battery Voltage Too Low and Warning 64: Low Battery. Error 04 occurs when the battery voltage drops below the minimum safe level, which can happen due to depleted batteries, a faulty cell, or loose and corroded terminals.
When this error triggers, the inverter will stop charging or supplying power until the issue is resolved. Warning 64 is a pre-emptive alert that appears before Error 04, giving you time to reduce loads and prevent unexpected shutdowns. Other battery-related problems can include poor wiring connections, aged or incompatible batteries, and incorrect inverter settings.
Regular inspection of battery terminals, monitoring the voltage, and ensuring correct configuration on your MUST inverter are key steps to preventing these errors. Maintaining clean, secure connections and using high-quality batteries from trusted brands like MUST or Sona Solar-approved models can significantly reduce the likelihood of interruptions, ensuring your solar system delivers consistent power when you need it most.
Common Battery-Related Errors
Most inverter errors are related to the battery. Proper battery maintenance and monitoring are essential for reliable system performance. Below are the most common battery-related issues you may encounter on a MUST inverter:
Error 04: Battery Voltage Too Low
The inverter detects that the battery voltage has dropped below the minimum safe level. This can happen due to depleted batteries, a faulty cell, or loose terminals. The inverter will stop charging or supplying power until the issue is resolved. Check the battery voltage, inspect terminals for corrosion, and ensure proper connections.
Warning 64: Low Battery Warning
This warning occurs before Error 04 triggers and is a pre-emptive alert that your battery is running low. It allows you to reduce loads and prevent the inverter from shutting down unexpectedly. Ensure that the battery is charged, and check for any connection issues or unusual voltage drops.
Other battery-related problems include poor wiring connections, aged batteries, or incompatible battery types. Regular maintenance, monitoring the battery voltage, and ensuring correct inverter settings can prevent most of these errors.
Faults: Fan & Temperature (01-02)
Error 01: Fan is locked when inverter is off
The inverter's cooling fan is obstructed or has failed. A foreign object may be blocking the blades, or the fan motor may have seized.
Error 02: Inverter transformer over temperature
The transformer has exceeded its safe operating temperature, typically caused by prolonged heavy loads or poor ventilation.
Faults: Voltage & Output (03-08)
Error 03: Battery voltage is too high
The DC voltage from the battery is higher than the inverter's limit, often due to incorrect settings or a malfunctioning charging source.
Error 04: Battery voltage is too low
The battery voltage has dropped below the minimum level due to depleted batteries, a faulty cell, or loose terminals.
Error 05: Output short circuited
A critical safety shutdown caused by faulty wiring, a malfunctioning appliance, or an internal component failure.
Error 06: Inverter output voltage is high
The AC output voltage is higher than the acceptable range, likely due to an internal regulation circuit failure.
Error 07: Overload time out
The inverter has supplied more power than its rated capacity for too long. Reduce the number of connected appliances.
Error 08: Inverter bus voltage is too high
The internal DC bus voltage has exceeded its safe limit, often caused by a sudden drop in load while solar input is high.
Faults: System & Relay (09-22)
Error 09: Bus soft start failed
The inverter's power-up sequence has failed, which usually points to an internal component issue.
Error 11: Main relay failed
An internal hardware failure of the main relay, which requires professional repair.
Error 21 & 22: Voltage sensor error
The sensor measuring the AC output (21) or grid voltage (22) is faulty. This is an internal component failure.
Faults: Sensor Errors (23-26)
Error 23, 24, 25: Current sensor error
A fault with the sensor measuring the output (23), grid (24), or load (25) current. This is an internal hardware issue.
Error 26: Inverter grid over current error
Excessive current has been drawn from the grid, possibly due to an external short circuit or internal failure.
Faults: Temp & Current (27-42)
Error 27: Inverter radiator over temperature
The heatsink has become too hot, usually caused by poor ventilation, a blocked fan, or sustained heavy loads.
Error 31: Solar charger battery voltage class error
A mismatch exists between the detected battery voltage and the inverter's settings. Ensure the correct voltage is configured.
Error 32 & 33: Solar charger current error
The MPPT's current sensor is faulty (32) or the charge controller cannot regulate the current (33). This is a critical internal fault.
Error 41 & 42: Grid voltage low or high
The incoming utility grid voltage is below the acceptable range (41) or too high (42), often due to a brownout or power surge.
Faults: Grid & Frequency (43-58)
Error 43 & 44: Grid frequency low or high
The grid frequency has dropped below (43) or exceeded (44) the inverter's safe operating range, indicating an issue with the utility supply.
Error 51, 52, 53, 55, 57: Internal system errors
These codes (Over current protection, Bus voltage too low, Soft start failed, DC voltage in AC output, Control sensor error) all point to serious internal hardware failures that require professional service.
Error 56: Battery connection is open
The inverter does not detect a proper connection to the battery bank, caused by a loose terminal, blown fuse, or disconnected cable.
Error 58: Inverter output voltage is too low
The inverter's AC output voltage is below the required level, possibly due to a very heavy load or an internal fault.
Warnings: System Status (61-77)
Warning 61 & 62: Fan is locked
The primary (61) or secondary (62) fan is blocked or has failed while the inverter is operating. This can quickly lead to an over-temperature fault.
Warning 63: Battery is over-charged
The battery voltage has exceeded the safe charging limit. The inverter will stop charging to protect the batteries. Check charging settings.
Warning 64: Low battery
A pre-emptive warning that your battery is low on charge. It appears before the inverter shuts down with Error 04. Reduce your load to prolong runtime.
Warning 67: Overload
The power being drawn exceeds the inverter's capacity. The inverter will beep before shutting down with Error 07. Reduce the load immediately.
Warning 70: Output power derating
The inverter is reducing its power output to prevent overheating, typically due to heavy loads or poor ventilation.
Warning 72 & 73: Solar charger stops (Low Batt / High PV Volt)
Charging has paused because the battery voltage is too low (72) or the PV input voltage from the panels is too high (73).
Warning 76 & 77: Communication or Parameter error
The inverter has lost communication with the charge controller (76) or one of its settings has become corrupted (77). A factory reset may solve a parameter error.
Frequently Asked Questions
How to set Must inverter settings?
Press and hold "ENTER" for 3 seconds. Use "UP"/"DOWN" to navigate programs, "ENTER" to select, "UP"/"DOWN" to change values, and "ENTER" again to confirm. Press "ESC" to exit.
How to reset a Must solar inverter?
For a soft reset, turn off Grid, then PV, then the inverter. Wait 1 minute. Turn on in reverse order. For a factory reset, find the reset option in the settings menu (consult manual).
What are the most common inverter faults?
Overload (07), Low Battery (04), and Over-Temperature (02, 27) are the most common. They are often resolved by reducing the load, allowing batteries to recharge, or improving ventilation.
What is error 7 on a Must inverter?
Error 07 is an "Overload time out." The inverter has shut down after running above its rated capacity for too long. You must reduce the number of appliances being used.
Still Having Trouble?
If you're facing a persistent error code or are unsure about a fault, it's best to seek professional help. Contact the Sona Solar Zimbabwe technical team for expert support and service.
Sona Solar Zimbabwe – Your Trusted Partner for Solar Energy Solutions
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