Introduction: DIY Electric Hand Warmer

Picture of 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

Picture of This Is All What You Need

Pipe

electrical tape

coppper wire 10metre 30swg

lithium ion battery

cardboard

basic tools

Step 2: The Main Structure

Picture of 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

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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

Picture of 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

Picture of 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

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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

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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

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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

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solder down all the electronic components according to the circuit schematic

Step 10: TESTING and Calculation

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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

voltage=3.92v

current=0.7A

resistance=5.6ohm

power=2.74w

runtime>3.5hrs

Step 11: Charge It Up

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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

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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

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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

Comments

gm280 (author)2018-01-04

I realize you didn't use nichrome wire because of its higher resistance per length. However, resistance, in this particular project, is a good thing. Why? Because a lower resistance requires a higher current draw and will deplete the battery quicker. Secondly, nichrome wire offers higher heat then copper wire. So if you were to rebuild your project using nichrome wire, you could get higher heat output for a longer time. It is how electronics works. JMHO!

parvgupta001 (author)gm2802018-01-17

Nichrome wire good for high temperature applications with focussed heating onto a very short area as greater resistance perunit length
Copper wire good for low temperature distributed heating as lower resistance per unit length and low melting point

parvgupta001 (author)gm2802018-01-04

Hello using nichrome wire could lead to a lesser no. of turns and thus uneven heat distribution but by using a copper wire of greater length we have achieved the same amount of resistance as in nichrome wire.and according to the law of energy either i use copper wire or nichrome wire both are gonna be emmiting same amount of energy (heat) for a given power input

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