Li-Po Battery to Power Heating Film

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dmichaud
 
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Li-Po Battery to Power Heating Film

Post by dmichaud »

Hello,

I would like to power a heating film (product info here http://www.cts-heater.com/31-cts-pet-005.html) used to maintain desired operating temperature range (between 0 degrees Celcius and 35 degrees Celcius) for handheld electronic devices while being exposed to ambient temperatures as low as -30 degrees Celcius.

The heater will deliver heat to the handheld electronic devices intermittently. There will be a feedback loop using temperature diode and a micro controller which will turn the heater on or off using a switch. The heating film can handle Voltage from 1.5 to 400V (AC or DC) and Power range: 0.07~2W/cm2

What specifications of Li-Poly battery would be appropriate for a system like this? i.e. 3.7V 1,200 mAh? or something more powerful?

Thank you very much.
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adafruit_support_rick
 
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Re: Li-Po Battery to Power Heating Film

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[Moved to General Project Help]

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adafruit_support_mike
 
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Re: Li-Po Battery to Power Heating Film

Post by adafruit_support_mike »

We can't give an accurate answer without knowing the thermal mass and heat dissipation of the system.

In general, applying 1 Watt of power for 1 second uses 1 Joule of energy. There are inefficiencies in any electrical system, but most of them involve converting power to heat, so in this case you can use the straight conversion for back-of-the-envelope calculations.

The more energy you have to pump into the system, the faster the battery will drain. Most LiPo packs are rated to supply energy at a rate that drains them in one hour, and that value is called 'C'. A 1200mAh pack could deliver up to 1.2A safely. Some packs are specifically designed to handle more power, and those will be listed by the multiple of C which you can safely use.. 2C, 5C, 20C, etc.

Draining the 1200mAh pack at 1C would release about 4.44 Watt-hours of energy, which is close to 16,000 Joules. It takes about 4 Joules to raise the temperature of 1cc of water by 1 degree Celcius. You're looking at temperature differences of about 50 degrees celcius, which would take about 200 Joules per cc of water. With the energy in a 1200mAh LiPo pack, you could heat about 80cc of water by 50 degrees celcius in an hour.

How that would translate to handheld electronics would depend on the mass of the device and the conditions in which you're working. If you don't have specific information about that, I'd suggest connecting the heating mesh to a plug-in power supply, putting it in the freezer with the kind of device it will need to protect and a thermometer, and seeing how much power you need to reach the temperatures you want.

dmichaud
 
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Joined: Sat Jun 07, 2014 12:30 pm

Re: Li-Po Battery to Power Heating Film

Post by dmichaud »

Thank you. That was very helpful!

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