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What are you really measuring as a battery discharges?

  1. Sep 30, 2013 #1
    Think for example a phone or any devices that shows the amount of battery power is left. It shows it as a graphic where you can deem whether it's full, 3/4 full, 1/2 full, 1/4 etc... or shows the actual percentage. What is that measure really showing you? Voltage? Amp hours left (which is the capacity I think)? And, how is it calculated?
     
  2. jcsd
  3. Oct 1, 2013 #2

    meBigGuy

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    As a battery discharges the voltage drops under load. This is mostly due to internal resistance increase.
    http://www.mpoweruk.com/soc.htm discusses it. It's possible to monitor this externally.

    But. most LI-ion batteries have an internal monitoring circuit that reports charge and discharge data back to the operating system. This is best because the data is so battery dependent.
     
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