# Help understanding secondary cells discharge curve

This is what I've understood about the process of discharging of a secondary cell. If I have a rechargeable cell, full charged, and I make it discharge at a certain constant current, let's say 1A, I will notice that its tension will go down since the EOL (end of life) tension. If I measure how much time the discharge process takes, let's say 1 hour, and if I multiply this value for the constant current, I get the capacity of the battery at that specific discharge rate (in this case the capacity is 1Ah). If I repeat the same experiment using higher currents I will obtain shorter time, but also lower capacity according to Peukert law, or some more realistic law. For example at 10 A I could get a capacity of only 600mAh. Often the constant current is written as function of the nominal capacity, so a discharge rate of 2C for a nominal capacity of 1Ah, means a discharge current of 2A. But what I really don't understand graphs Tension-Capacity, like this one:

Following my previous argument, given a certain discharge current the capacity is uniquely determined while tension stays inside a certain range. I wuold draw something like this:

Any help is very welcome.

• Is that a postage stamp glued to your page? Commented Feb 27, 2020 at 14:25
• Well it would be easier to read if it was a bit larger.
– user16324
Commented Feb 27, 2020 at 14:33
• The graph seems to agree completely with your written understanding. Can you be more specific about what is confusing you? Commented Feb 27, 2020 at 14:35
• mAh capacity at a given current (curve) is the x axis value where each curve crosses the 3.0V line. Commented Feb 27, 2020 at 15:01
• I didn't realize the graph was so small, hope this new one will be readable @Andyaka Commented Feb 27, 2020 at 16:42