Introduction: DIY Electric Hand Warmer
LITHIUM ION battery powered hand warmer
please open and view all the images as their is fairy useful information as text on them too
Step 1: This Is All What You Need
coppper wire 10metre 30swg
lithium ion battery
Step 2: The Main Structure
using hack saw or angle grinder cut a metal pipe piece of greater length and diameter than the 18650 battery.
then smooth out any rough surfaces of the pipe.
Step 3: Maintain an Air Gap
Lithium batteries don't work very well in very hot temperature and thus to avoid a greater temp to reach the battery maintain an air gap by putting in a piece of cardboard with honeycomb shaped air gaps which would extend the battery life of our warmer.
start by measuring and cutting a piece of cardboard and then fit it inside the pipe giving the battery a better fit
Step 4: Adding Wires to the Battery
SPOT WELDING is the best option to attach wires to lithium batteries but here we cant get that and thus for that reason you can even solder wires to the battery but consider making the soldering iron hot tip contact with battery terminal for the least amount of time.
Step 5: Heating Coil
Measure a copper wire of 30swg and 10metre in length.
30swg wire offers a electrical resistance of 0.5ohm per metre of length
copper wire is used here because it has a lower resistance than the nichrome wire and thus more of it can be wound which gives a very even heat distribution throughout.
also copper wire is very easily available in any kind of motor or as the transformer winding .
start by winding it around the metal pipe with a even distribution of the wire throughout the pipe so that their is a proper distribution of heat throughout the heater,
then tape up the winding so that it looks good and the wires stay in place
Step 6: Removing the Insulation
copper wires are usually varnished for insulation.
we need to remove that from the ends for connections
start by burning up the varnish layer and then rub it off using a fine grit sandpaper
Step 7: Electronic Components
this here is the circuit schematic that is used to make the hand warmer
maintained spst switch
2.1mm power plug female jack
general purpose diode 1n4007
Step 8: THE DIODE
the diode here is a very important component as it acts as a very simple charging solution for the lithium ion battery
the diode have a voltage drop of 0.7v which provides a safe charging voltage for the lithium battery when connected to a 5v power supply.also it slows down the charging process as it decreases the charging process according to its datasheet.
Step 9: Electronics Components
solder down all the electronic components according to the circuit schematic
Step 10: TESTING and Calculation
after testing we can calculate the power output of the heater ie 2.74watts
on a single cell it will give a runtime of greater than 3.5hrs
Step 11: Charge It Up
Using a power bank or any other 5v power supply simply charge it by attaching a 2.1mm male power plug on the charging side.
takes about 1 hour to fully charge the battery
Step 12: COMPLETE
seal up everything in place by filling all the gaps with hot gluegun
The test results show a running temperature of 40 degree Celsius after heating up for a minute.
Step 13: Thanks for Watching
if you like my this project be sure to check out my other instructables
any doubts or questions can be asked in the comment section below
for a more detailed view of the entire project you can refer to this youtube video---https://youtu.be/pso2blTd7Xg