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Getting power from coin cells

Posted by Terry Moore
Terry Moore
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on Friday, 02 December 2011
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Buried on TI's website, there's a very nice white paper on practical considerations for getting power from coin cells: "Coin cells and peak current draw,"

The author, Mathias Jensen, obtained CR2032 coin cells from a variety of vendors, and tested how much energy could be obtained in a variety of circumstances.  His key findings:

  • CR2032 cells have varying real capacities (based on the vendor).
  • Because of internal resistance, if you need bursty power, you should add a capacitor that can be trickle-charged at low current.

Out of politeness, he probably didn't mention some important additional conclusions:

  • Customers are going to buy batteries based on convenience and price, not based on vendor.
  • Many batteries don't nearly acheive their rated capacities in real-world tests.
  • If you want your customers to be satisfied, you have to design for the worst-case battery, not for the best-case.
  • Careful design for the worst-case battery can result in 1.4 times the battery capacity with low-quality batteries.

This is the kind of detail that, properly attended to, makes the difference between products that are loved, and products that are merely used.

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