Quick question: all my protected batteries when fully charge show ~4.12V... there is one though (one year old battery) that won't go anymore past 4.05V. Is this a sign that I should sooner or later retire it or I can keep on using it without a problem?
i have a 18650 that wont charge over 4.0v i now use it in one of my single cell lights with on issues
Is this the voltage after the cell has rested for a hour or so off the charger. Whats the voltage right off the charger.
Not all chargers charge the same way. They can have different charging methods as well as terminating voltages. Li-ions do best when charged with the proper CC/CV charging algorithm.
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This post by 45/70 is a guide which I general use. It does depend on what method the charger used for charging as the terminating voltage can vary.