Are battery specifications for open circuit or closed circuit conditions?
I understand that a battery connected to a load will have a multimeter reading of low voltage, due to the voltage dropped on the internal resistance of the battery. Thus, if I have an open circuit voltage Vbat = 3.6v and connected a load, I could measure a lower voltage. I also read that the current draw and temperature affects this.
I am particularly interested in Lithium ion cells. Most datasheets I read specify: Nominal voltage: 3.6v Max charging voltage: 4.2v Cut-off voltage: 3.0v
Are these voltages in open circuit (and *rested) condition or loaded condition?
*I read that loaded batteries, when removing load will have their voltages rebound and stabilize after a few hours or so. Say I have a loaded battery with Vloaded = 3.0v. When I remove the load, the open circuit voltage becomes higher (3.3v) and will continue rising and stabilize only after a few hours.
Background/Reason for asking: I want to test a certain charging circuit to see if it can charge healthy fully discharged batteries. By healthy, I mean batteries that were discharged up to their cut-off voltage only (not to 0v). In order to this, I am going to discharge the battery cell (taking into account the max discharge current from datasheet) up to their cut-off voltage by monitoring the loaded voltage. Once I see that the loaded voltage ~3v (cut-off), I am going to remove the load. But when I remove the load, I see that the open circuit voltage becomes higher and continues to go higher until it stabilizes after a few hours. I need to know if the specified cutoff = 3v is the open circuit rested or the loaded voltage. If its the former, then it means I would need to keep discharging/removing/resting the batteries until I finally get a rested open circuit voltage of 3.0v.
