Powering an Arduino off of 12 Volt Car Battery

5V car adapter charger for cell phones

I recently acquired a few old cell phone chargers that are designed to plug into cars. Theses small devices have turned out perfect for my robotics project because they are designed to connect directly to the 12 volt output of a car battery and convert it to about 5 volts. A 12 volt car battery will fry small electronic devices like an Arduino but if I wire these two cell phone chargers in series than I can have enough voltage to power an arduino off of the 12 volt car battery. This is an improvement because I am currently using a separate 9 volt battery to power the robot's Arduino.

The setup was very simple. To do this you don't even have to remove the plastic outer case of the charger like I did. Just connect the end of the charger to the positive battery terminal and one of the side connectors to the negative side of the battery. Then just cut and strip the wire on the end of the charger. There is 5V output between the red and black wire (red being positive +, and black being negative -). There is also about one volt between the red and the white wire. I thought this was a bit odd because electronics don't usually use a positive wire as a common line.