Watch out for cheap car phone chargers
I decided to buy a 5 volt phone charger for my car to fit in the cigarette lighter. Before plugging my phone in I wanted to make sure it worked so I plugged in a USB volt/current meter to see what the output was. I found that it was 14.1 Volts. Although I'm sure my phone has built in overvoltage protection I'm still glad I didn't end up plugging my phone in.