Candle Powered Phone Charger

https://www.youtube.com/watch?v=17VU2FkfDOM

According to the first law of thermodynamics, heat that flows from a hot object to a cold object is energy. An invention called a Peltier Device takes this energy and converts it to a form of electricity. Peltier devices can be found inside USB drink chiller/heaters. Using these principals, we can create a device that charges a cell phone using the heat from a flame lit lamp.

Parts List

Here’s a main list of parts and approximate prices:

Part name Price
USB drink chiller $10-$20
Sterno Cooking Fuel $10-$20
Single AA Emergency Phone Charger $10-$20

If you want to create a metal stand like I did in the video, here are the parts I used that I found at a local hardware store:

Part name Quantity
1/4 Inch Hex Nuts 8
1/4 Inch Threaded Metal Rod (7-8 inches) 4
Electrical box face plates 2
1/4 Inch washers 4
1/4 Lock washers 4

Although it’s not required, it’s helpful to have a Multimeter so that you can read what voltage is being output.

Obtaining the Peltier Device

Peltier Devices

Inside of the USB drink chiller is a peltier device. In it’s current state, it will take electrical impulses and cool down one side of the device while the other side of the device heats up. This is what cools down the drink that is sitting on top of it. But we’ll be using it for the exact opposite of this: we’ll be heating up one side of the peltier device and cooling down the other so that it outputs electricity.

To remove the Peltier device, just unscrew the bottom of the USB drink chiller. You will probably see a bunch of wires and a heat sink. Unscrew the heat sink, if necessary, and underneath it you will find the Peltier device. You should see a black wire and a red wire coming from the Peltier device. Cut these wires being sure to leave at least a few inches attached to the Peltier device.

Constructing the stand

The metal stand serves multiple purposes. Not only does it provide a nice platform for the Peltier device to sit above the fire, but it helps distribute the heat more evenly across the Peltier device.

Metal Stand Parts

I used two metal electrical box faceplates to increase the thickness and heat distribution. Most faceplates have 4 holes or notches so that you can easily attach screws, or in our case, metal rods. On each threaded metal rod, place one nut and one lock washer. Adjust the nut and lock washer so that they’re about 4-5 inches from the bottom of the metal rod. Then slide the rods through each of the holes on the faceplates so that the faceplates rest on the lockwashers. The faceplates should now be standing on the metal rods about 4-5 inches above the surface of the table. Lastly, place one washer and one nut over the top of each metal rod and screw them down to secure and stabalize the faceplates.

Completed Metal Stand

The Set Up

The set up is pretty simple. With your stand, place the Peltier device on top of the faceplates with the wires safely hanging over the side. Place a lit flame underneath the faceplates so that it starts heating up the Peltier device. For best results, place a heat sink directly on top of the Peltier device to help keep the opposite side cool.

If you have a multimeter, connect it to the two wires of the Peltier device to get a voltage reading.

Adding the Voltage Boost

Since it’s hard to get the Peltier device to output more than 1.5 – 2 volts, we need to use a voltage booster to jump it up to 5 volts, which is the standard voltage required to charge most cell phones. The necessary voltage booster can be found in an Emergency Phone Charger that uses only one AA battery. For mine, it was very simple to unscrew the Emergency Charger and remove the component that boosts the voltage.

Noticing which part of the AA battery (plus or minus) touches which part of the voltage booster will allow you to determine which side is positive and which side is negative. Once that is determined, you can use alligator clips, or soldering equipment to attach the negative wire of the Peltier device to the negative terminal of the voltage booster. Do the same for the positive wire and the positive terminal.

Go ahead and plug your phone into the voltage booster. Once the voltage of the Peltier device reaches 1.5 volts, the phone should start charging.

 

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16 thoughts on “Candle Powered Phone Charger

  1. erich says:

    Cool use of a peltier device and step-up transformer!

    Bonus points for the Thermodynamics!

    One point here, as it relates to thermodynamics, is that the amount of work you get out of a given energy source depends, not on the quantity of energy in the source, but on the difference in energy concentration between the energy source and the environment. This difference is sometimes called ‘exergy’. A petroleum product like the jelly in your sterno can, or a lump of charcoal, for that matter, have higher exergy than your typical candle.

    This is the main reason that, while the total energy falling from the sun onto the earth is greater than our total current energy needs we currently service by burning fossil fuels (billions of years of stored sunlight), it is impossible with our current, massively wasteful. methods of power distribution and consumption to maintain our current standard of living with solar power generation: the exergy is too low. Each individual photon of light has the same energy that it ever has, but collectively, those photons are diffusely spread out over half the globe at any time. Concentrating them takes work.

    That said, I wonder how you might use relatively diffuse waste heat to generate 1.5 volts? Now that’s a sustainable hack!

    A few ideas that come to mind:

    Put the peltier device at the center of a solar oven?

    The center of a compost pile often gets pretty hot due to anaerobic digestion…

    Burn garbage to turn a windmill/propeller, to drive an alternator?

    Keep up the cool posts!

  2. Josh says:

    You can get a 40mmx40mm peltier device from SparkFun for $15. That way you don’t have to mess around with dismantling the drink chiller. Lots of good thoughts for implementation in the comment section as well.

  3. Pat says:

    What kind of amps are we talking? That’s just as important as the voltage. My phone takes 1A to charge, so if this thing is only putting out 200mA, then it’s going to take quite a long time to charge it.

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  5. Jenna Fox says:

    I’m also wondering what the output current is. It looks like those AA charger doodads put out about 250ma when running on an AA battery, but how much current does it get with the candle?

    I’ve found a deal on ebay for two peltier plate gadgets for less than twenty dollars, so I’m hoping to stack them and get a bit extra power out of it, or maybe use the second one for a DIY solar charger!

  6. rozie says:

    What is minimum temperature for this device to operate? I mean in what temperature it starts to produce around 1.5V? I ask, because I’ve heard such a devices require pretty high temperature to operate. And they’re very inefficient comparing to normal ways of producing electricity from heat (consider carbon dioxide production). If this would start work at let’s say 50-60C it may be worth to consider “recycling” part of energy from laptop CPU to extend it’s battery life.

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  8. WakonTonka says:

    The suggestion to find the specs & work out the possibilities for using a Peltier device to scavenge energy from the heat in a laptop’s interior gets one to consider other things that would benefit from such a scavenge. Turbosuperchargers have been doing this principle for quite some time on piston engines & steam turbines.

    Thanks for revving up my # of processes running…..

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