# I recently have needed a way to monitor my battery voltage levels for a

(Jon Burroughs) #1

I recently have needed a way to monitor my battery voltage levels for a RC type LiPo battery pack. If the voltage goes too low, it goes BOOM. The batteries lack a protection circuit, and that’s just the way they come. From my google-research, I have found this site that has the most precise information regarding electronics and voltage dividers monitoring battery levels. Would the experienced @Ashley_M_Kirchner_No or experienced EE please vet this information for me? Is this approach to monitoring voltage levels, up-to-par so-to-speak? Thank you!
https://startingelectronics.org/articles/arduino/measuring-voltage-with-arduino/

(Mike Thornbury) #2

Yep, that’s one way to do it. It’s safe and reliable for voltages over 5V.

If you read off the LiPo balance plug, you can read the voltage for just one cell, which will nominally be 3.7V, so you shouldn’t need a voltage divider circuit. Check the pins on the balance plug to make sure you are getting gnd and one cell +ve, then you can calibrate your reading to match the measured voltage and you will be fine.

Just connect the live LiPo pin to your analogue pin, the gnd will already be in-circuit, through your power connection.

(Ashley M. Kirchner [Norym]) #3

So the idea here is that you are creating a voltage divider for the Arduino. Particularly if your battery pack is above 5V. There are plenty of calculators online that will tell you what your resistor sizes need to be based on the battery voltage and what you want to read in. For what it’s worth, I raw raw battery power into my one project because it’s a single sell, 4.2V at the most. The analog pins can handle up to 5V, and it’s a 10-bit resolution, so you can map 0-1023 to 0V-5V and get your voltage just by reading that. It’s the poor man’s way of doing it, there are better ways.

(Andrew Tuline) #4

Jon, can I assume then that you’d use some sort of library (such as narcoleptic) to put the Arduino into sleep mode when the voltage is below a certain threshold?

(Jon Burroughs) #5

Thanks for the help guys. This battery is nominal 11.1v, so I need a divider. The balance port will be too far away from the board to connect to.

(Stephen Beeson) #6

You should add a 1n capacitor in parallel with R2.

It will reduce noise, make up for the >10K impedance of your circuit which will improve accuracy.