Discharge rate chart for LiPo?
Is there some sort of chart that shows battery voltage vs. current available in an LiPo battery? For instance, if an open-circuit voltage is taken on a 3 cell pack (3S1P), which is suposed to be 11.1 volts, actually reads somewhere around 12.6 volts when fuly charged. As the battery is discharged through a load, let's use the ESC and motor as an example, the battery is drained down. Let's say that I use the battery for 8 minutes. Normal usage has throttle settings vary during the operation (in flight for RC Electric Aircraft) and servo's as well as the motor consume power.
Ok. With that said, after running for this 8 minute flight, I want to know how much has been used and, obviously, how much is left.
Let me give some additional info. I may not want to use the battery again, but am finished for the day, and have flown, lets say, three flights. I have four batteries. I want to know what the condition of these batteries are in before I put them to the charger. I don't want to put the fully charged battery back on the charger because it's not safe to 'top off' fully charged LiPo batteries. So, I take my trusty voltmeter, or even a WattsUp gadget, and measure the voltage. I will see that the fully charged battery is about 12.6 volts so I can put that aside and go to the rest of the batteries. But, suppose the last flight was only, say, 30 seconds, and for some reason, I terminated the flight. This operation may only have consumed a portion of the current available so the voltage reading may still be somewhere around 12.6 volts, but the battery has been discharged somewhat.
Is there a chart showing the percentage for a particular pack.. let's stick with the 3cell (3S1P) LiPo that has a nominal voltage of 11.1 volts and go from there. What does 11.1 represent? How aboutg 11.2? 11.3.... and so on up to max charge of, say 12.66 volts?
I know it's not linear, but is somewhat close for a good percentage of the discharge rate, but would like to know if there is something or somewhere that this information is available.
I guess I could sit down and record this myself using the WattsUp gadget and Excel but perhaps someone out there has already done that and has the answer.