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Thread: What's The Empty Voltage Of A 7.4V Li-Ion Battery?

  1. #1

    Default What's The Empty Voltage Of A 7.4V Li-Ion Battery?

    Can anyone here tell me the voltage of an 'empty' 7.4v Li-Ion battery? I'm trying to diagnose if a camera battery is dead.

    Thanks.

    Z.

  2. #2

    Default Re: What's The Empty Voltage Of A 7.4V Li-Ion Battery?

    First, there is no such thing a a 7.4 Volt Li-Ion cell.
    Your battery is an assembly of 2 x 3.6 Volts Li-Ion cells.
    So even if one cell is still intact, and you get a reading of 4.2 Volts, this means not that the battery is OK!
    One of the cells might be defect, and the other might be OK, and the battery as an assembly will not be working in your device.
    Try to recharge your battery, and see if you can get a reading of more than 7.2 Volts from it.
    If you cannot, your battery is gone!
    Even also if each of your cells still can get a voltage up to more than 3.6 Volts fully charged, it is not sure they can deliver any power when in use!
    This you can only check doing a reading when your battery is under a load.
    So you need more knowledge than just the ability to do a voltage reading, to find out if your battery is dead!
    Or maybe just recharge it and put it in your camera and see if it works?

  3. #3
    *Flashaholic*
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    Default Re: What's The Empty Voltage Of A 7.4V Li-Ion Battery?

    mostly empty it would read More than ~6v if its still working right.
    max discharge on it would be ~5V most cams wont take it down that far, and it should bouch back up some when the load is removed.
    when fully charged it should be reading close to 8.4V

    like labrat said, and from what it already sounds, if it isnt running your device well it is probably to aged, out of balance or just finished. even if it shows good voltage, if it doesnt charge, self discharges, or doesnt hold good capacity (have runtime) not only is it dead, but its not concidered totally safe Either.

    charge it, run it down, charge it again if it aint working , its dead jim.
    potentially you can change the cells and restore it to better than new, but some curcuits placed on them make that harder than it looks.
    Last edited by VidPro; 08-27-2009 at 06:17 AM.

  4. #4

    Default Re: What's The Empty Voltage Of A 7.4V Li-Ion Battery?

    Thanks for the help folks! I should have the battery in my hands soon, and with it maybe more silly questions!

  5. #5

    Default Re: What's The Empty Voltage Of A 7.4V Li-Ion Battery?

    Fully charged and hot off the charger it reads 8.25v. Any thoughts on that?

    Thanks.

    Z.

  6. #6
    *Flashaholic* Mr Happy's Avatar
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    Default Re: What's The Empty Voltage Of A 7.4V Li-Ion Battery?

    Quote Originally Posted by Ziemas View Post
    Fully charged and hot off the charger it reads 8.25v. Any thoughts on that?
    That's a perfect fully charged voltage, just over 4.1 V per cell. Now let the battery sit for a day or two without touching it and measure the voltage again. If the voltage stays above 8.2 V the battery is behaving well, but if the voltage drops below 8 V the battery is bad.

  7. #7

    Default Re: What's The Empty Voltage Of A 7.4V Li-Ion Battery?

    I let it rest overnight and the voltage is 8.04v, so I guess it's dead. Thanks for the help folks!

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