Build Your Own Car Power Inverter

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A car inverter will take the 12 volts DC from your car; usually from your cigarette lighter and turn it into 110 volts AC, which is what you get out of your home power outlets. This allows you to plug household electronics into your car. the most common would probably be your laptop. Home UPS systems do the same thing, except instead of using a car outlet they use a 12 volt battery. I used a old home UPS system I had laying around that had a bad battery. (We don’t use the battery in this mod)

Preparing the UPS

Here is the UPS before any modifications:


Only half of the outlets on the device are given power from the UPS system, the rest act as a regular surge strip. The first thing I did was rewire the “surge” outlets to be wired into the UPS power so that all of the outlets would be provided power from the UPS system.

Inside UPS

Next I took a car plug adapter I had lying around and connected it to the battery terminals after removing the battery.

UPS with car plug


The UPS system was working and outputting ~106 volts AC from a car’s 12 volts outlet. Here you can see it in action with my meter and a wireless router.

Testing inverter with meter

This worked great, but the UPS has a buzzer in it which stayed on. The purpose of this buzzer was to notify you that your power is out and that you are on battery power. However it serves us no purpose and is just really annoying. I fixed it by unsoldering the buzzer from the main circuit board.

Some Final Modifications

In addition to movie the buzzer, I also wanted to make the device smaller as half of it is empty space due to the lack of a battery.

I started my moving two of the LEDs that are on the batter end over to the power switch. I moved just the Power and Overload LEDs, the rest served no use for an inverter.


I used a pipe saw to cut of the battery compartment, there was already a divider on the inside that would now act as the outside wall on that end.

Final UPS

This ups works perfectly as a power inverter. I have used it on several road trips just fine, And because it was intended to be a computer UPS, it can power 350 watts, which is much more than your average car inverter.