battery monitoring system voltage level multiple cells in series

hello and thank you in advance.. i will try to show you the full picture of the project that i am thinking to do. i have a lead acid battery stack of 120 cells connected in series. each cells voltage is from 2.08 to 2.70 volts.. what i want do is make a circuit with the arduino which shows me the voltage of each cell in the computer.. if this is somewhat difficult it could simply record a voltage measurement from each cell every half hour. the measurement does not need to be at that time exactly for all cells. it is enough, for example, to record the measurements within 2 minutes. i think because i have a lot of cells, so the voltage dividers are excluded. what i am asking from the forum is to suggested me some tested ideas ! thank you again!

Hello,

You need a flying capacitor circuit.

Have a look at reply 4 and 5 of this https://forum.arduino.cc/index.php?topic=333321.0

You could do a long string of voltage dividers feeding a bank of multiplexers feeding into ADC chips or ADC input on an Arduino module such as a Nano, or a Mega clone.
MCP3008 would be a good 10-bit ADC with 8 inputs
https://www.digikey.com/en/products/detail/microchip-technology/MCP3008-I-P/319422
with SPI interface, it is capable of faster conversions than the ADC of an Arduino or Mega.
12 and 13 bit versions are also available
https://www.digikey.com/en/products/filter/data-acquisition-analog-to-digital-converters-adc/700?s=N4IgjCBcoGwJxVAYygMwIYBsDOBTANCAPZQDaIALGGABxwDsIAuoQA4AuUIAyuwE4BLAHYBzEAF9CAWgjQQKSBhwFiZcAFYADMzadIICdIBMieVH4BXFSUjl1IQghYgOXQyCkI5Cy9bURnV30JSRATWxB0ABMUJnEgA

Another way is to isolate each battery with relays or optocouplers (such as a PVT412 SSR from Mouser).
You will need 120 relay or opto drivers (such as 15 of TPIC6C595), and would need to ensure only 1 was turned on at a time.
This would be the equivalent of moving a set of probes from a multimeter across each battery individually.

The Arduino Gnd would not be connected to the Battery Stack Gnd.

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