Why is my inverter always in battery charging mode?

There might be two reasons for it.

if battery is more than 5 years old than it may be weak and not producing required voltage so that inverter can cut off the charging, so inverter can not stop charging.
Secondly check the backside of the inverter. There is a small switch which indicates UPS mode and normal mode. If it’s on UPS mode than change it to normal mode and problem will be solved. Some inverters have voltage range selector on the backside of inverter. if your inverter has this selector than set the voltage selector to 100–300 voltage range. If it doesn’t work than kindly mention the inverter model and battery model and hopefully it can be solved.
And do not forget select charging Amp selection for battery charging selection setting you can also read my other blog or you visit my YouTube channel