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How to determine which battery is new one?

  1. Sep 11, 2013 #1
    I have 2 batteries for my mobile, and forget which one is new and old.
    The standard volt is 3.6 V, and I measure the voltage using any standard electric meter.
    Battery A has 3.86V
    Battery B has 3.77V

    Does anyone have any suggestions on whether it is possible determine the new battery based on measured volt or not?

    Thanks in advance for any suggestions :>
  2. jcsd
  3. Sep 11, 2013 #2


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    Can you charge both to 100%? Otherwise, I would expect the charge state to be more significant than the age.
    Do you have a small resistor? Something like ~50 Ohm. Connect it to the two terminals, and measure the voltage while the load is applied. A better battery will have a smaller voltage drop compared to the setup without load.
  4. Sep 11, 2013 #3
    I get following meter, will it be possible to measure it using this device?

    Do you have any suggestions?

    Thanks you very much for any suggestions :>

    http://www.uni-trend.com/UT10a.html [Broken]

    http://www.uni-trend.com/manual2/UT10A%20Eng%20Manual.pdf [Broken]
    Last edited by a moderator: May 6, 2017
  5. Sep 11, 2013 #4


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    Staff: Mentor

    That is a simple voltage measurement, every multimeter can do that.
  6. Sep 11, 2013 #5

    Yeah... look at the serial numbers on each battery. I'd bet the larger serial number is the newer battery.
  7. Sep 11, 2013 #6


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    there we go !! what a brilliant answer :smile:

    you really cannot go by voltage as the older battery may still be capable of charging to its new condition maximum. And apart from that, there's likely to be minor variations in full charge voltage of new batteries anyway!

  8. Sep 12, 2013 #7


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    The best way is to see which lasts longer in the cell phone.

    The only other way I know of is to measure the internal resistance by applying a load and measuring the change in voltage.
    Both batteries should be fully charged and then partially discharged to around 3.7V. Then measure the voltage drop when you apply a 33 ohm resistor. The lower voltage drop is the better battery.
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