To be more specific, the source voltage needs to be 5v with 1000mA or 1A.
Your laptop almost certainly provides that with a USB 2.0 port (unless of course you have a macbook pro ARGH!). eHuman is right in the sense that most usb wall/car chargers are trickle charging at no more than 500mA wich won't get the PT going.
Find a usb car adapter rated at 5v - 1A and you'll be set.
How do you figure only 1 amp?
5v <- source voltage
2.6 (ish) ohms <- atty resistance
Ohm's law: V=IR
5v=I(2.6 Ohms)
I=5v/2.6 ohms
I=1.92 amps
even assuming 3.3 ohms (cartomizer):
I=5v/3.3 ohms
I=1.52 amps.
Theoretically, If you use a normal atty (2.6 ohms) at 5v, with only 1 amp max current flow, it will be roughly equivalent to vaping at 2.6 volts, assuming the power supply is not capable of being over-stressed.
In reality, the power supply will provide more than 1 amp, but you will stress the power supply (read: overheat), and heat and electronics NEVER play nicely together.