i am designing short term (>60sec of backup) UPS circuit based on supercapacitors for my low power i3 intel computer (12V, 5W). All i need is to provide safe turn off for my system in case of power outagge. So when main power goes off, usb command triggers computer shutdown process, which takes average of 45sec. The circuit is composed of 4x 2.7V 20F capacitors that feed power to my step up converter (boost converter can hande 10W at 4.2 to 12V input to provide steady 12V output).
In order to keep all capacitors at same voltage when charging, i thought of jsut using an already integrated low power MCU that i alreay use to control some signal LEDs, to simply watch individual capacitor votlages and in case of overvotlage appearing anywhere, jsut using mosfet to discard capacitor via proper sized resistor.
Are there any problems that i missed, with the attached circuit?