VEVOR Power Inverter, 2000W Modified Sine Wave Inverter, DC 12V to AC 120V Car Converter, with LCD Display, Remote Controller, LED Indicator, AC Outlets Inverter for Truck RV Car Boat Travel Camping

We need to know if 11.8v is display voltage or battery voltage.

Hello, the fuse is a spare.

This 2kW modified chord inverter does not have the "inverter/charger with bypass" function.

Yes, it can run a garage door opener in most cases. A typical opener uses ~300–600W running with a higher short surge, which your 2000W inverter can handle. If this answer does not resolve your current issue, please contact us again for assistance.

You can use longer power cables, but they need to be thicker cables, otherwise they will generate severe heat.