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  1. #1
    Join Date
    Nov 2005
    Posts
    15

    NiMH Battery Charge Level.

    I know this is kinda off topic byt anyaway: Can you post some links or tell me how to build a circuit for the testing the charge level of a NiMH battery. How do cameras know when to display the "low battery icon"? I was told that a simple voltage measurement with a voltage meter means nothing? So how do i do it? Does it have something to do with the current which you can drain from the battery at that moment?
    Any help appreciated! THX

  2. #2
    Join Date
    Jul 2004
    Location
    Formerly South Wales. Now South Carolina.
    Posts
    7,147
    Quote Originally Posted by Vlatko
    I know this is kinda off topic byt anyaway: Can you post some links or tell me how to build a circuit for the testing the charge level of a NiMH battery. How do cameras know when to display the "low battery icon"? I was told that a simple voltage measurement with a voltage meter means nothing? So how do i do it? Does it have something to do with the current which you can drain from the battery at that moment?
    Any help appreciated! THX
    A simple voltmeter doesn't give you anything but volts which only drop when the battery is very low. Think of the battery current as water running through a pipe. It can be running very fast (voltage) but not at a very high pressure (amps). What you need to do is to measure the pressure (amps) to see if that's dropping.

  3. #3
    Join Date
    Jul 2004
    Location
    Boulder, CO
    Posts
    138
    Quote Originally Posted by Rhys
    A simple voltmeter doesn't give you anything but volts which only drop when the battery is very low. Think of the battery current as water running through a pipe. It can be running very fast (voltage) but not at a very high pressure (amps). What you need to do is to measure the pressure (amps) to see if that's dropping.
    Um, I think that pressure is the dual of voltage, and flow is the dual of current. Pressure makes the water flow throught the pipe, just as voltage makes the current flow through a wire.

    I don't know how cameras that use NiMH batteries determine state of charge, but it's more likely voltage than current. The voltage would be measured while current is being drawn from the battery.

    Other methods would be battery impedance or milliamp-hour integration, but these are somewhat sophisticated.

  4. #4
    Join Date
    Oct 2005
    Location
    Australia
    Posts
    40
    Quote Originally Posted by Robert Besen
    Um, I think that pressure is the dual of voltage, and flow is the dual of current. Pressure makes the water flow throught the pipe, just as voltage makes the current flow through a wire.
    Yep

    V=IR correlates to Pressure = Flow X Resistance

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