Heated Jacket Liner

This is a DIY heated jacket liner for use under our motorcycle jacket.

It was constructed by stitching a 20 foot length of heater wire from a defunct electric blanket to the inside of the red windbreaker. The green windbreaker was sewn inside the red one to protect the wires.

The white wire is the heating element. The black one is an 18AWG wire running from one end of the heating wire to the external connector at the bottom of the jacket.
Here is the routing of the wires.

The electric blanket wire is a twin conductor wire. Each conductor is made of a pair of 36 AWG strands spiral wound around what appears to be a nylon fiber core, and coated with a plastic insulation of some sort.

The external connector is a 5.5 x 2.1 mm DC power connector - similar to those used for laptop computer power supplies.

Each conductor of the heating wire has a room temperature resistance of approximately .24 ohms/foot. In the jacket, the two conductors are wired in parallel, giving a total resistance (with connections) of approximately 2.5 ohms. At 12 volts, the current starts at 4.8 amps, resulting in an initial power of 58 watts.
As the jacket heats up, the resistance increases slightly, dropping the power to around 47 watts. That is pretty low for a jacket; 70-90 watts is more typical. But as this was the first try, 47 is acceptable. It produces a noticeable amount of warmth.