Inverters are essential in converting direct current (DC) from a battery to alternating current (AC) to power household appliances and office equipment requiring AC to operate. Inverters are limited by their conversion capacity and the charge capacity of the battery bank.
A beeping sound emanating from the inverter is a warning signal that something is wrong with the inverter or the battery bank. The cause may be due to the following:
- Wrong battery cable size
- Reduced battery capacity
- Overloading of devices
- Failed self-test
- Running on battery mode
- Low voltage
Let’s look at how to diagnose and correct each failure mode and protect your equipment from damage.
Why The Wrong Battery Cable Is A Problem For The Inverter?
One of the most frequent problems with inverter installations is that the incorrect gauge (AWG) wires cable connects the battery to the inverter. Copper wire cables that are too thin or too long will result in a voltage drop between the battery and the inverter.
A too-thin wire will result in inadequate current strength, and an excessive cable length will result in voltage drop to the inverter. A high-pitched alarm will sound and indicate that the battery cable size needs to be increased and shortened.
To determine the correct size and length of cabling to connect the battery bank to the inverter, you have to consider the power rating (Watt Rating) of the inverter. The maximum watt rating will be indicated on the front of the inverter.
Let’s assume that your inverted is rated as a 5000W 24Vdc power inverter. This means that the inverter will generate AC to power 4000W (5000W less 20%) of power drawn from AC appliances connected to it from a 24V DC battery bank.
The inverter watt rating divided by the battery bank voltage will provide you with the current strength between the battery and the inverter. In this example 5000W / 24 V = 208.33 A (Amps) based on Ohm’s Law (W = V x I)
The maximum current that will be possible between the battery bank and the inverter is thus 208.33 A. From a conversion chart, we can see which size cable is required to conduct 208.33 A safely. A 1 AWG has a maximum amperage rating of 211 A, which is too close for comfort, so that we will select a 0 AWG cable with a maximum amperage of 245A.
The thicker gauge cable will also limit voltage drops over a longer cable distance. Thicker and shorter cable connections are always better between the battery bank and the inverter.
Reduced Battery Capacity Causes Your Inverter To Malfunction
A depleted battery bank will cause the inverter to sound an alarm by beeping to protect the battery bank from becoming too deeply discharged and protect both the battery bank and the inverter from damage.
The inverter is warning you that it can no longer function as required due to the battery bank’s insufficient state of charge. The inverter needs to be shut off, and the batteries must be allowed to be recharged from either a solar array via a charge controller or via a grid tied battery charger.
Lead-Acid batteries must not be discharged below 50% of their full capacity as this will cause damage to the batteries and reduce their recharge cycles. Lithium-ion technology batteries can be fully discharged, but it is recommended that their state of charge be maintained between 20% and 90% for prolonged battery life.
Once the charge controller indicates that the battery bank has been recharged, you can switch the inverter on again and resume powering the appliances connected to it. If the beeping alarm persists, the cause is not a depleted battery.
Continue troubleshooting to determine the cause of the being alarm.
Overloading The Invertor Will Result In Beeping Alarm
We have established that the battery and inverter are connected with the correct size cabling and that the battery bank has a state of charge (SOC) within their operational range.
The next most likely cause of an inverter alarm beeping is that you have loaded too many devices to the inverter and that the combined power demand exceeds the maximum capacity of the inverter.
A solid beeping tone will persist until you have disconnected enough devices to bring the power demand below the inverter’s maximum power output. It is recommended to allow a safety margin of 20% below the maximum rated capacity.
For a 2000W inverter, do not draw more than 1600W from the inverter to maintain a safe operating condition. For 3000W, connect only 2400W of power draw; for 4000W, connect only 3200W of power draw; and for 5000W, connect only 4000W of power draw.
Inverters Run A Self-Test Cycle Before Converting The DC to AC
Inverters are programmed to run a self-test before switching on the total power demand in AC from the DC power source. This self-test can be programmed to run every four or five hours and accompanied by rapid beeping.
AC inverters are programmed to perform regular self-tests to check on the integrity of the battery bank. If the battery bank is getting old and the state of charge cannot be maintained within the operational range, the self-test cycle will alert you to this condition.
The expensive decision to replace the battery bank has to be made if the inverter continuously fails during the self-test cycle. Converting to battery chemistry with a more extensive operational range and more recharge cycles is expensive but ultimately the lowest cost solution.
The Inverter Will Beep When Running In Battery Power Mode
When the grid power goes down, and the inverter switches on to supply the connected devices with power, this will be announced by the inverter by four beeps every thirty seconds during the power transition.
This is not a persistent beeping and will stop after a few minutes. The beeping alarm alerts the power users that they are now running on battery power and that efforts to prolong the power supply to crucial equipment should be taken.
Only leave critical equipment connected and limit their use to extend the battery state of charge.
Inverter Alarm Due To Low Voltage
A beeping alarm with a fixed frequency every five seconds indicates that a low voltage condition exists. To prevent a sudden loss of power, start to power down and switch off connected appliances.
The low voltage alarm is likely due to a loss of charge in the battery bank and warns you to stop the inverter before damage is caused to the battery bank. If you have failed to identify the cause of a persistent alarm, contact an electrical contractor to come and investigate.
The cost of a call-out will be significantly less than the potential damage that can be caused if inverter alarms are left unattended.