Question regarding "MultiCell Voltage Monitoring for Lithium Battery Pack" project

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Bo Tod's picture


Joined: Apr 30, 2020

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Question regarding "MultiCell Voltage Monitoring for Lithium Battery Pack" project
April 30, 2020 - 8:38am

Hi all, 

So I have been looking through an interesting project that I found and have started trying to build it myself. Even after a couple of hours spent trying to understand one part of the schematic that the creator posted I am stil struggling to understand it's purpose. 

So the creator makes use of a voltage divider in his schematic and then connects it to a header called "P1" (I have highlighted it in the imgur link). he then takes the output of that voltage divider and connects it to pin "A0" on the arduino nano that he is using.

He makes use of pin A0 in order to measure the voltage of the entire battery pack, however, in his code when he uses the measurement from pin A0 in order to display the "Measured Voltage" battery pack he does not account for that original divider. Based on his values of the first resistor in the divider being 10k ohms and the second resistor being 1k ohm I am caclulating that the output of the divider would have a value of 1.45V(when the pack is at a full 16V capacity). 

Then in his code for the arduino he just multiplies this value by 4 in order to get the total "measured voltage", so at full capacity it would be a value of 5.803, which is far from what it should be at 16 volts. 

Code for the arduino:  lcd.setCursor(0, 1);

  float Pack_Voltage = analogRead(A0) * (5.0 / 1023.0) * 4.002; //Measure the total pack voltage 

  lcd.print("Measured:"); lcd.print(Pack_Voltage);

Can anyone explain what the purpose of the divider is and if he just makes a mistake in his code to not account for the orignal divider? Any ideas or thoughts be really helpful. This is the link for his project

Thank you so much in advance.