When an inverter battery is fully discharged, there are a few steps you can take:
1. Disconnect any devices from the inverter to prevent further draining.
2. Connect the battery to a charger designed for that battery type.
3. Allow the battery to charge for the recommended duration until it reaches its full capacity.
4. Avoid overcharging the battery, as it can lead to damage.
5. Once fully charged, reconnect the battery to the inverter and check if it powers your devices properly.
6. If the battery doesn't hold a charge or fails to power devices, it may need to be replaced.