Do you want to stay warm even in a light sleeping bag? With the carbon cord heating element on you can increase your sleeping bag rating by 10 degrees.
The carbon cord is very soft and does not interfere with sleeping. Unlike nichrome wire it can withstand multiple bending. You can expand and collapse your sleeping bag again and again and carbon will never break.
I improved my sleeping bag in just one hour, see how easy it is.
Step 1: Shopping List
1. A sleeping bag you would like to improve.
3. 12V dimmer.
4. 15 feet of wire. I like ultra flexible silicone wire 18 AWG.
5. Duct tape.
Step 2: Just Wrap It!
For our project we used 6 pieces of 5 feet of carbon rope 3mm. A large length (30 feet total) of heating elements provided uniform heating.
But the most important thing is that a large number of segments provided a small electric current on each of the elements (about 0.4 Ampere). With such a small current it is very easy to ensure a reliable contact between carbon cord and electric wire. Simply strip a small section of wire and wrap it around the carbon cord.
1. Open the sleeping bag and evenly distribute the carbon rope on the inner surface, as on the photo.
2. Prepare several lengths of wire and lay them as shown in the photo and on an equivalent circuit.
3. Strip wires at the intersection points with the carbon ropes and wrap it tightly.
4. Connect female power socket plug connector.
Step 3: And Just Duct Tape It!
Secure carbon ropes and wires with duct tape.
With such a length and voltage of 12 volts, the carbon rope will only heat up to 30-40 degrees Celsius. At this temperature the duct tape will not melt or peel off.
I've already used this electric heated sleeping bag in several hikes and the duct tape is still securely in place. It is soft enough and does not interfere with sleeping. The volume of the collapsed sleeping bag did not change. I think this is a good solution for express DIY designs but in the next project I want to use a sleeping bag with a detachable lining to sew the carbon cord to the lining.
Step 4: Just Power It and Stay Warm
I had a very inexpensive summer sleeping bag with a comfortable temperature of +15 degrees Celsius. After installing the heating it became comfortable even at a temperature of +5 degrees Celsius. The carbon cord emits nearly 30 watts of heat. This level is typical of commercially available products. For example Ravean sleeping bag has about 40 Watts.
Using a dimmer, I can smoothly adjust the temperature and the run time. Carbon heated sleeping bag can be powered by the most of 12v USB power banks, but you can also connect it to any of 12-24 volt power supply. For example, to the power adapter of your laptop, to the car battery. The carbon cord heats up in a few seconds, I climb into the sleeping bag, press the button and immediately feel the warmth both above and below.