I want to power an LED that has a 3.3V forward voltage using two 3V CR2032 coin cell batteries to create a 6V supply. I set the resistor for a 20 mA current. For my application, the LED will be turned on for about five minutes a day.
The CR2032 has a capacity of 235 mAh (Energizer datasheet: http://data.energizer.com/pdfs/cr2032.pdf) The datasheet only has a "continuous discharge characteristics" curve for a 0.19 mA drain.
How do I know what the capacity is at the current draw level of 20 mA? How can I estimate the battery life, besides dividing the mAh capacity by the current draw?
It's confusing because on some sites I've read that coin cell capacity seriously degrades if you continuously draw more than a few mA... but I've seen many keychain LED flashlights that even use the smaller capacity CR2016 battery.