Interested in making a cheap AC inverter out of parts you can often get for free?
If you happen to have a broken UPS backup computer power system lying around (or can find one cheap), you could possibly turn it into an inexpensive power inverter for your camper.
Uninterruptible Power Supplies are often thrown away or donated to thrift stores when their battery goes bad. Once they do, you could simply replace the dead battery with your RV's deep cycle battery and enjoy a decent quality inverter that often -- at least on newer ones -- includes 5V USB power for your phone -- in addition to several standard AC outlets.
I actually did this, after watching the video below that I found on YouTube. It's an interesting project. The main idea is simply to unhook the leads going to the internal battery and then solder in some leads that will connect to an external battery. The most elegant solution -- to make it function like a store-bought inverter -- would be to run small leads to screw terminals on the outside of the case.
The second simple bit of electronics is to turn off the emergency alert -- the high-pitched squeal that normally is designed to warn you when the electricity goes out and you're running on battery power -- and you can disable it simply by finding the small buzzer element and cutting the leads and removing it.
There are other hassles you can run into. I found the outside case can sometimes be unreasonably difficult to crack open. You might also find that the circuitry is already fried, or in such bad shape that it sizzles or breaks as soon as you connect the battery. But after a few, you might just find one that opens easily and works really well.
The one big disadvantage for a small camper is the weight -- the transformer inside is quite heavy, especially on large UPS units, and especially when compared to the lightweight transformer-less inverters you can buy on sale for $40-80.
It's also no less prone to shorting out -- A badly-timed surge can fry any inverter pretty easily, so it's nice to have the option to exchange it for a new one. Then again, it's also nice to know you can build one for next to free, so it's well-worth learning how to do it!
(Note: Modified Sine-Wave AC output by cheaper UPS inverters may not be suitable for all devices. For quickly charging your laptop and mobile electronics, it should do fine, but for continuous power, beware that it could cause problems, so be sure to google and download the UPS manual. If you're concerned about this, check out his next series on how to make a sine-wave inverter. )