Nathan Dornacher had returned home from a yard sale with his family when the Samsung smartphone set alight.
The Galaxy Note 7 was left in the Jeep to charge with the air conditioning running, while Mr Dornacher brought his newly purchased desk inside the house.
Writing on Facebook about the incident, which took place in Saint Petersburg, Florida, Mr Dornacher explained: "We were planning on grabbing the dog and Bonnie and heading to PetCo.
"I head back out to the car to grab my phone which was on the charger go to open the door and see flames inside."
Firemen were able to contain the blaze, which tore through the Dornacher family Jeep, Mirror reported.
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