DIY Electric Hand Warmer

LITHIUM ION battery powered hand warmer

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This Is All What You Need

Pipe

electrical tape

coppper wire 10metre 30swg

lithium ion battery

cardboard

basic tools

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.

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

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.

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

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

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

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.