# Battery cell voltage measurement ADS1115

Hi Gents,

I'm new in this forum and I hope I can get some answers from you experts

I want to measure cell voltages fom a series of batteries but I'm struggling with the ADS1115. Even not sure if the ADS1115 is the best solution for this project.

I have 6 cells in series (see example picture). So fat I've used ESPeasy but there I can only select to measure to GND or 0-1, 3-0, 3-1 or 3-2. If I made the code myself would it be possible to measure anything against anything? For example 2-3 instead of 3-2? As far as I understand right, I can measure only positive values?

As I need to measure 6 cells I need to use 2 ADS1115 connected to a wemos d1 mini . The cell voltages should be within 5 volts each.

Thanks a lot!

xxx_turbo_xxx:
The cell voltages should be within 5 volts each.

What battery chemistry, what are the cell voltages, or what is total max stack voltage.

You could measure stack voltage and voltage on each tap (six total), and calculate each cell voltage.
But that requires voltage dividers on each tap (to 2.048volt for the ADS on 3.3volt),
and that creates uneven cell drain, which could be a problem.

The "Flying capacitor" method is another way (higher resolution, no cell drain),
but that requires relays or special (expensive) ICs.
Leo..

6 identical dividers using precision resistors is probably the way to go. You can share the botton
resistor of the divider after an analog switch chip if you want, as that node will always have a
safe voltage.

Forget trying to do floating measurements, its just too complicated to be practical in a fixed
circuit. This is why the resistors need to be precise as you have to subtract values to determine
each cell's voltage. 1% is the worse precision to contemplate.

The max voltage you have there with all batteryâ€™s is about 9v

You could with a voltage divider , measure that with a resolution of 9mV .
So why not just do that and switch in the batteries as you wish ( use FET?).

Note that if you run batteries in series , they will end up being discharged at about the same time anyway, and you wouldnâ€™t want to replace just one - so just measure the top voltage ?