Inverter Fit

Inverter Fit

Help with car inverters.?

I need an inverter for my car. I expect to draw 70W of continuous power from it it. My car says it has a 120W max. What size do you buy? All the inverters that I've seen with any quality are 400W units. How do these work? How close does the size need to be to fit the application? Do they try to use more power, the bigger they get or what?

A car inverter takes your 12v direct current battery power and digitizes it into a 120 volt alternating current sine wave. If you buy a 400 watt inverter and are only using 70 watts, that is fine. You will still be only burning 70 watts. The 400 watt rating only means that it's fuse or overload breaker will kick in if you use something that draws more than 400 watts. And if your car has a 120 watt max, your car's fuse will blow (I'm assuming your are running it through your cigarette lighter) if you draw more than 120 watts.

Excessive current (I=P/E, but that is beyond the scope of this answer) will burn out a fuse or trip a breaker, but that is what breakers and fuses are there for, and the breakers will keep you from harming any of your electrical equipment. Also remember to run a small in-line, plug-in, surge protector if you are running any sensitive electrical equipment like a laptop.

I use inverters all the time in my work truck to charge my computer/cell phone/battery chargers. I have a big fancy one that I rarely use, and a small simple one that seems to work great for everything.

Just go for it, but remember, at 70 watts you will drain your battery fairly quickly if your car is not running.

Good luck Brudda-man, invert-away and enjoy.