I have a 4500 watt power inverter. Bought it over 20 years ago, for about $300. I always carry it with me, in my van, truck , or car... whatever I own.

I have always had some kind of power on my vehicles (for power tools etc).

I use to rewire alternators and have 110 volts.. Did that for thirty years. You had to run your engine, where the inverter draws direct from battery. I have used the inverter to power up gear for several hours without a major draw on the battery.. Warning gauge will let you know if you are low on power.

BTW: for light power usage check out Ryobi inverter , uses standard 18v battery.. it has 1 or 2 outlets and quick swap of batteries when needed. ($100).