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I wish to measure 14S battery voltage on each cell with single ADC. I guess I need some ADC built-in or external (I2C), voltage divider and switch chip that will allow me to select one of 14 pins to measure.

Am I correct?

Could you advice what switch chip should I use?

or Should I build that curtuit myself with 2 74HC595 and mosfets? (not sure if that will ever work)

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    You may want to search on the term “analog multiplexer”. Sep 28 at 11:31
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I would do it manually (but then I am a bit sadistic like that).

The circuit for one cell is pretty simple, and you just need to replicate it 14 times. A P+N pair of MOSFETs to switch a battery channel on and off, and a pair of resistors to make a voltage divider. You can keep the "lower" of the resistors common between all channels if you like to reduce the number of components and complexity, but once you have 14 channels the complexity will become pretty silly anyway. Here's an example with just 3 channels:

schematic

simulate this circuit – Schematic created using CircuitLab

You would need to size RA|RL, RB|RL and RC|RL (etc) accordingly to get the right voltage ranges for the ADC input, and keep the output impedance low enough (<10k) for the ADC to handle it properly. You may want a couple of different load resistors (RL) for different groups of cells.

All the N-channel MOSFETs could be replaced by a 4-to-16 decoder with open-collector outputs (such as, if you can get it, the 74xx159), which would also protect against switching on multiple channels at once, which you never want to do.

Note that this arrangement gives you the voltage of the first cell, the voltage of the first two cells, the voltage of the first three cells, etc. To get the voltage of just the third cell (for example) you will need to subtract the voltage of the lower cells.

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