Using a really old 140 watt inverter in 2012 V's 12-volt ?

Should be fine, I wouldn't worry at all.

 

As long as the inverter isn't broken, it should work in any car's 12V outlet.

 

First, realize that inverter is 140w which means it could attempt to draw well over 14 amps if loaded. Some designs may draw a lot of amps on startup as well. So don't even think about adding much load just because you have an AC output. Second, most low cost inverters put out a modified square wave and call it AC. True AC is a clean sine wave. Never put a motor load on a modified sine wave and some transformer loads like in power supplies may get hot. The best thing to do is to test and ensure the Prius' limited amp outlet can take it and the load does not get hot.


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Don't even dream of pulling 140W for even a few moments. The inverter may be fine, but the Prius 12V 'cig lighter' outlet is likely to blow its fuse.

These outlets were originally meant for only 10A, or 120W. While some vehicles have these upgraded to higher currents, the Prius doesn't seem to be among them.

Anything over 100W on the inverter output is likely to require 120+W on its input, the reasonable limit for the car's 12V outlet.

 

Definitely check the laptop's power supply requirements. Mine is only 85 watts, but yours might be much higher.

As long as the computer can work on the output of the inverter, and it won't pull too many amps, you should be OK. Just don't get carried away and plug more stuff into the inverter.

Honestly, though, we haven't taken our inverter long in decades. Charging the laptop overnight seems to get us through the day fine since our phones are now so capable.

 

Another idea would be to purchase a car adapter for your laptop. They’re available for most popular models.

That way you’re not adding the losses from converting 12vdc up to 110vac and back down to low laptop voltage (which is maybe 20vdc).

There are ones designed for specific laptops, and also semi-universal models like this one.

 

Worse, some put out a sawtooth wave that will absolutely kill most electronics.