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measure individual battery voltage when they are in parallel ?

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rompelstilchen

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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

Untitled.png

Thanks
 

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
 

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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