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Author Topic: Monitoring Battery status using an arduino  (Read 1122 times)
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Chennai, India
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I'm building a project that requires me to monitor a battery and switch over to another batter when the 1st battery runs low. Now I can build this using op-amp like on the arduino board. What i require it to be able to monitor the level of charge left. This would means i would require to somehow hook up the battery to an analog input and monitor it. How can i hook up batteries of any voltage or current ratings? Also i would love to add a display to show how long the battery will last for the whatever application it is being used. Something similair to a lap-tops battery level indicator.

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There is an Arduino for that
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To hook your batteries up to the arduino board you just need a voltage divider to scale their output voltage to the dynamic the arduino is expecting. Depending on the board you are using it should be 3.3V or 5V. And of course the arduino board should be powered with a well regulated power (not the battery).

Concerning the time left it is all but simple. It is function of battery charge level and current consumption. If you want an accurate value, at any time, you need to know how many charges remains in the battery and how many current you are consuming. For a simple display you can use the voltage. But be aware that on many batteries the voltage stays at nearly the same voltage for all the discharge cycle and suddenly ramps down.
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Measuring a voltage is simple, for batteries I do not expect low levels requiring amplification. Just use a voltage divider if it is more than 5 volts (Arduino Vcc).
For measuring a current (or charge) you need a shunt and op-amp. A charge is an integration of a current in time - this can be done by software. There are of course IC (from Maxim i.e.) which contain shunt and op-amp inside.
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