I am considering replacing the coin battery in my shield design with a super capacitor. I wonder if someone else is doing this already. Any comments/suggestions?
I'm using DS1307. It has a maximal I_battery of 500nA, maximal V_batt 3.5V. I intend to use the Arduino 3.3V supply to charge it to 3.3V. The minimal V_batt is 2V.
I guess using some math I'm looking at some time t that is acceptable for temporarily removing the power for no more than a day or so and then reattaching power.
I found that with a 0.22F supercap, it lasts 6.6 days. Am I too optimistic?