6 ways to test if your inverter is working properly
Operating equipment
The quickest and easiest way to test an inverter is to run the device you want to power.
Simply plug in all the devices you want to run and turn them on. This will tell you immediately if everything is working properly. I also recommend letting it run for a few minutes to make sure your inverter doesn't get overloaded or overheated.
One thing to note is that some larger inverters above 1000 watts have a power saving mode. This means if your power consumption falls below 50 watts, they will shut down. So, this could be the reason why your inverter is not able to charge small devices like mobile phones, laptops or tablets.

Check LED lights
A reliable way to check if your inverter is working properly is to look at the LED lights that appear on most devices. Typically, this will be a green light and a red light.
If the green light is on, all systems should be operating normally.
If the red light comes on, there is a fault that requires further investigation.
Use digital display
Many modern inverters now include digital screens to give you more information about operating status. This can help you identify any issues as you will be able to check information such as input voltage, battery status and output power.

wattmeter
Another neat trick is to use a wattmeter. You plug it into the inverter's AC outlet and then plug the device into a wattmeter.
The benefit of this is that you will have a real-time reading of how much power your devices are able to draw from the inverter. If it's lower than expected, you know you've got a problem.
Also, investing in a wattmeter can be useful if you plan to run more equipment. It allows you to quickly find the battery usage of any device.

Multimeter
A multimeter is a handheld device that can be used to test electrical circuits. They are so useful that electricians use them every day for diagnostic purposes.

Using a multimeter, you can check voltage, current, and resistance. This will help you diagnose any issues with your inverter, battery, and appliances. You can have fun testing wiring systems, motors, appliances, circuits, and power supplies.

Replacement battery
To test the inverter, you can easily try it with another battery. This way you will know if there is a problem with the inverter or your power supply.

Simply unhook the current battery and connect it to the other battery in the same way. If you don't have another deep cycle battery, you can always use the vehicle starting battery in the same way (if you do this, make sure to keep the engine running so you don't drain the starting battery).