Vcc Measurement of Supercapacitor cells using ATtiny85 / Optocouplers and MUX

Hello all,

I have 4 supercapacitors which I want to wire in series. I’m proposing the following circuit to measure Vcc of ATtiny85 and send to Master Arduino. Each cell will get a ATtiny85, which will be in sleep mode unless “woken” by M.A. Two optocouplers will separate high and low energy circuits. I will have 5 sets of these four supercaps + circuit in series (20 caps total) so I will be using an Analog Multiplexer to minimize ADC pins.

My question to this community is whether this approach is correct and if there are any tweaks needed.

Cheers All!