My girlfriend often waits for a bus during 20-30 minutes. There is -5°C...-20°C sometimes. And today I want to show you my solution.
In the video you can see the test of this boots in beautiful New Year Helsinki.
Pleasant viewing :)
Step 1: I Used:
1) Wool Insoles like this:
2) Heating Nichrome Wire. I used 0.4mm:
3) Batteries Li-ion 18650:
4) Power Bank Case (5V, 1A):
5) Hand made USB powered cable for 5V, 1A.
6) Sewing Elastic Rubber 40mm:
Step 2: Nichrome Wire.
I cut 65 cm of nichrome wire. It takes 5V, 0.7A for one foot. Insoles warm up to +49°С.
Step 3: USB-cable
I tested some USB-cables, but they could transfer only 0.5A unfortunately. And I made my own.
Step 4: Soles + Wire + USB-Cable
I sewed the wire and USB-cable to insoles. Nichrome wire couldn't solder, so i used needle with thread.
Step 5: Batteries
I used new li-ion batteries 18650. I tested it's capacity = 3400mAh! It's great :)
Let's calculate battery live time.
Battery has 3.7v and 3400 mAh, but Power Bank voltage transformer gives 5V.
So battery into case should has capacity: 3.7*3400/5 = 2516 mAh.
The nichrome wire "eat" 0.7A, so battery live time: 2516/700 = 3,6 hours. Voltage transformer efficiency, I think, 90%, so we have 3,6*0,9 = 3,24 hours.
It's about 3:15.
Will check it latter.
Step 6: Temperature Test
I got 21°C (without nichrome wire) and 49°C (with). Cool!
Step 7: Put Inside
Step 8: Strap
I sewed straps using 40mm rubber and velcro.
Step 9: Results
Hid under jeans :)
Step 10: Conclusion
We tested heated boots in Helsinki on the New Year holiday. It is a beautiful city! But it was so windy.
We were walking about 8 hours every day. And these boots were saving Masha.
Masha is happy. Me too :)
Live test showed they are great boots, don't causes discomfort. Live time about 2-3 hours. We didn't check the exact time.
But USB contact was bad. I want to change it to other connector type.
PS: Sorry for my bad English, I am still learning. You can correct me (please).
PSS: It's my first instruction, so I will be happy to read your opinions ;)