Re: Low battery indicator

Discussion in 'Digital Photography' started by MA, Sep 3, 2003.

  1. MA

    MA Guest

    > Can anyone explain for me why my digital camera shows a low battery
    and
    > switches off when using rechargeable batteries (that have been charged

    up
    > fully - discharged first) after only taking 20 pictures yet lasts

    longer
    > with cheap alkaline batteries - 16 for £1 (1 english pound) ?


    I think rechargeable batteries have different discharge characteristics
    than alkaline batteries. Alkaline batteries keep their voltage at, for
    example, 1.5 V during their whole lifecycle, while rechargeable (NiMH)
    drop to around 1.2 V quickly and then operates at that voltage. If you
    look at your rechargeable ones they are probably marked 1.2 V? I know I
    have seen some camera manufacturer releasing new firmware for use with
    rechargeable batteries where the low-battery warning is adapted for that
    use. Look at the manufacturer's homepage to see if there is a new
    firmware version, I do however think it is strange that the camera also
    switches off.

    Best regards, Magnus
    MA, Sep 3, 2003
    #1
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  2. MA

    Jack Mac Guest

    On Wed, 03 Sep 2003 16:15:44 -0500, Ron Hunter <> wrote:

    >Graham wrote:
    >> Ron Hunter wrote:
    >>
    >>>Not exactly. Alkaline batteries start at 1.6V and decrease to about
    >>>1V (where most cameras cut off) over a relatively steady rate of
    >>>decrease (fairly linear).

    >>
    >>
    >> So a camera which takes 4 x AA might be set to cut off due to flat
    >> battery at 4 x 1.0V = 4.0V
    >>
    >>
    >>>NIMH batteries start at 1.35 (a slight overcharge as their
    >>>'chemical' voltage is 1.25 volts), and then drop to 1.25V in a few
    >>>minutes, and remain there until they are about 90% discharged and
    >>>the voltage drops to about 1.1 volt.

    >>
    >>
    >> So a set of three fully charged NiMH AAs and one really sick one might
    >> have a total voltage of 3 x 1.35V + 0.5V = 4.55V
    >>
    >> Within a few minutes of use this might fall to 3 x 1.25V + 0.2V = 3.95V
    >> and the camera would decide they were flat and shut down?
    >>
    >> This can be tested by measuring the individual cell voltages.

    >You would need to place the batteries under load to get a good reading.

    You can tell a bad cell by comparing the open cell voltage.
    Jack Mac, Sep 4, 2003
    #2
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