I would like to ask if there is some easy enough way to calculate Li-Ion battery capacity if I measure the discharge time with constant load (not constant current!).
I have made a "discharger" using arduino, relay and 3.9ohm resistor. I measure time from start (4.2V) to 3.3V and then disconnect the battery using the relay. I get the time in seconds on the display.
I know the best way would be saving voltage through the discharge cycle and then get the capacity using integral. My mathematics skill is too low to make it there (maybe programing skill too).
Is there easier way to use? Could I simply do it by:
Voltage / Load * Time
What voltage should I use in this calculation? 3.7V?
Are there any other ways?
(I can't switch to constant current method because I already made the discharger and put some effort, time and money in it. I don't want to leave it and start over)