Almost everyone carries one of those LED head lamps. They last forever and, as you may have seen, have an added benefit. They make fire. That’s if you have a bit of steel wool or other fine wire.
The principle is simple and will work with most electronics (including a cell phone battery). Inside your LED lamp you will have a cartridge which should contain 3 AAA batteries. On one side there will be two contacts which connect to the lamp itself. In your cell phone, you have a Lithium Ion battery. You take your steel wool and you place one end on one contact and one on the other. All you’re doing is completing a circuit. Because the wire is so fine, you will actually overheat the wires and they will glow red.
Just put your steel wool in your tinder bundle and blow it with a sustained current of air and voila! You might not spend the night cold.
I’ve had success with this using the battery from a cellphone and a headlamp, but it is much easier with a headlamp battery cartridge.
Do you carry tinder? What do you use?