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!

ATtiny_Opto_MUX_Bus-1.png