A 18650 battery is charged up to 4.2V on XTAR X4, why it doesn’t show FULL?

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xtarflashlight
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A 18650 battery is charged up to 4.2V on XTAR X4, why it doesn’t show FULL?

A customer told us he charged his 18650 battery up to 4.2V on XTAR X4 extended, but the charger didn’t show FULL (still at 80%) on the screen. Then, he moved the 18650 battery into another slot, and it immediately showed 100% and FULL. He asked: Shall consider the 18650 fully charged at 4.2V independent of showed percentage, or wait until the screen shows FULL? Did his X4 charger display inaccurately?

Actually, his X4 chargers still works fine. As there is 1% accuracy error of the charging cut-off voltage on each slots, the cut-off voltage (4.16~4.24V) varies slightly between different slots. If the cut-off voltage on one slot is 4.16V, and we assume his 18650 battery’s real-time voltage is 4.18V, the charger will judge the battery is fully charged and show FULL, when putting the battery in that slot. While, if he move the battery to another slot with cut-off voltage of 4.24V, the charger will charge the battery for a little longer time, then cut off. But please don’t worry, the judgement accuracy error is very small, and it will not affect the fully charging of the battery. As XTAR charger can intelligently judge a battery is full-charged or not, if you check the “FULL” on the screen, it means the battery gets fully charged.

As for the reason why the charger doesn’t accurately display the charged volume, the charger shows the percentage of the charged volume to be 20%, 60%, 80%, 100%, and it can’t show the accurate percentage like 98%, 99%. Take above customer’s question for example, his 18650 battery wasn’t charged fully, but almost (e.g. 95%). So it remains at 80%. When the battery is fully charged, the screen will show FULL and 100% in charged volume percentage.

F. Premens
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My VC4 charges all batteries to 4.22v, but for precise charging or to know exact voltage I use the VP1.