I've noticed as li-ion cells age, their ability to receive a full charge goes down. so a charger that keys on voltage alone will keep attempting to charge until set volt is reached.
when you remove cell from charger after termination to end voltage. cell will quickly drop.
just repeated this with a protected R123 cell charged to 4.1v and repeated to 4.2v. both instances cell dropped to 4.02 after removal.
when you remove cell from charger after termination to end voltage. cell will quickly drop.
just repeated this with a protected R123 cell charged to 4.1v and repeated to 4.2v. both instances cell dropped to 4.02 after removal.
SilverFox said:When the cells are healthy, this should not present any problems, however as the cells age they will be subjected to a trickle charge for an extended period of time. ~
Back to the aged cell. The cell is considered "dead" when its capacity drops below 80% of its initial capacity. The reason the capacity drops is because the internal resistance of the cell goes up. This increase in internal resistance limits the maximum voltage of the cell. This means that it spends more time holding the constant 4.2 volt as the current tapers off. If your current never shuts off, you can effectively trickle charge it for quite a while as the cell struggles to stay at 4.2 volts.
As soon as you remove the cell from the charger, the voltage will drop on a cell with increased internal resistance. Your cell may have been charged to 4.2 volts, but when you take it off of the charger it may drop down to 4.12 volts, or something like that.
Tom