Hey guys total noob here. I have this 4S li ion battery, i would like to monitor each cell with my arduino. I dont have enough available analog input pins on board so im planning to use ADS1015 to measure each cell and pull the data with I2C interface.
Where im struggling to solve is how to connect each cell to ADS1015.
Currently i have a balance plug connected to the pack so i can get 4.2v-8.2-12.6-16.8v respectively relative to the packs negative.
I cant connect them directly because my logic is 3.3V so i have to use voltage divider for each cell. First cell is ok i can just connect it by dividing the value by 2 with resistors and multiply it by 2 on the arduino side.
for the second cell im getting confused.
can i connect 2.cell’s voltage divider reference to 1.cell’s positive side so i can still make the calculation from 4.2v and use the same resistor values all across for every cell? In this case on each hop i wont get more than 4.2v per cell and my formula on arduino side will be the same for each cell
i should use common ground and adjust each cell’s voltage divider circuit in a way that they wont exceed 3.3v and use the resistor values in arduino side for calculation for each cell. also in order to find cell 4 voltage i will have to measure and sum all 3 beneath it and subtract them from the 4th cell in order to find the value.
Im not sure which one is acceptable or even if they would work correctly. i attached both schematics for both cases in order explain it better.