Battery charge voltage and current
In my charger reviews I often comment on a high termination current, and says that the battery will not be fully charged, but I do not specify more precise what that means.
In this test here I have taken a battery and charged it with many different charge settings and then measured the capacity and energy in the battery. All the measurements was done on automated equipment, i.e. voltage, current and timing was exactly the same in each test, except the charger termination setting. For the test I have used a fairly new AW18650-26 cell:
The charger started at 1.3 ampere and followed a perfect CC/CV curve until the specified limits.
After charging the battery rested for one hour.
The discharge was done at 1 ampere and stopped when the battery was down to 2.8 volt.
In the table the green line is what a typical hobby charger will do at the 1A LiPo setting.
Plotting the voltage after 60 minute versus capacity shows a very good correlation:
As can be seen from the table, both the termination current and termination voltage is very significant to get the most energy from the cell. The downside to filling the cell completely is lifetime, a cell with a high resting voltage will wear down a lot faster and this will happen even if it is not used.
Note: This test was done while I was finalizing my setup for LiIon battery testing, my final setup does charge the battery to a slightly higher voltage.