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  1. #1
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    measure individual battery voltage when they are in parallel ?

    Hello,

    I build a system based on arduino, the thing is powered by two 9v batteries in parallel, for longer operation and battery hot swap

    I wanted to know if it was possible to measure individual battery voltage (to display on an lcd) ?

    since both + poles are connected together I can only measure both batteries

    would adding a diode do the trick ?

    here is a quick sketch I made

    Click image for larger version. 

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    Thanks

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  2. #2
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    Re: measure individual battery voltage when they are in parallel ?

    Hi,

    If the batteries are connected in parallel --> both batteries will have the same voltage.

    And if your idea is to temporarily disconnect both batteries to do the measurement, then I don't think you will gain some information from the two measurements.

    What's the idea behind this setup?

    ******
    Now you say "hot swap".
    Then I recommend to use a mosfet for each battery...controlled by the microcontroller.
    Or at least an "ideal diode" device not to waste too much energy.

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



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  3. #3
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    Re: measure individual battery voltage when they are in parallel ?

    no, it's clearly intended for live measurement

    I guessed , measuring one battery, no current from the other battery would flow through that diode,

    so I would have expected that, before the diodes, the battery voltage would remain intact

    I meant by "hot swap", having a battery replaced while the system is runing upon the other battery



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  4. #4
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    Re: measure individual battery voltage when they are in parallel ?

    ok I gave it a try, diodes made the trick



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