The Mighty Volt said:
I have a PITA standing around trying to charge A123 via the CV method, where the voltage is set to 3.6v from my power supply, and then observe as the current drawn by the battery decreases, until it eventually hits 0.01A, CV. At that point it is, in my opinion, fully charged.
However, it is taking an age to move from 0.10A to 0.01A, 3.6v CV. So, I ask, what is the difference in SOC at these values? Is it so insignificant, as I can safely connect these batteries in parallel without suffering any damage to the lesser charged cells?
Check out the first post in my A123 capacity/charging thread: http://endless-sphere.com/forums/viewtopic.php?f=14&t=20698&start=0#p301558
I charged some A123 cells with a CC/CV charger (constant current/constant voltage). The CC phase was set at 6 amps. With the 2300 mAh cells, the cells would ideally fully charge in 23 minutes, but the chemistry does not allow that. At 18 minutes the charger started the CV phase where the pack voltage remains constant and the charge current drops. It took another 18 minutes to reach the recommended cutoff current of 50 mA.
So just how much extra capacity does one gain in the final CV charge phase. A fully CV/CC charged cell had 2305 mAh capacity. The same cell that was charged for only the 18 minute CC phase had 2093 mAh. You gain around 9% capacity from the final CV phase (that takes as long as the constant current phase).