Factors affecting the charge time of 18650 Li-ion batteries

XTAR Light

XTAR Light

Apr 26, 2010
Charging time of the 18650 Li-ion batteries can be about 1.5 to 4 hours depending on several factors. These factors affecting the charge time of the batteries include as below.

*The battery capacity: With all other factors constant, a 18650 battery with a higher capacity, will take longer time to charge compared to one with lower capacity. For example, a 1800mh battery can take about 1 to 1.5 hours to charge whereas a 3500mah battery may take about 3 to 4 hours to be fully charged using the same adapter.

*The power output of the charger: Comparing with a fast charger with 10W (2A, 5V) output power, using the common 5W adapters will charge the same batteries in almost twice the time.

*Battery temperature: High battery temperature may slow down charging or reduce lifetime of the battery.

*Battery internal resistance: The lower the internal resistance, the faster for the battery to charge. For example, the batteries tend to lose capacity as they age, also the internal resistance increasing, then it may need more time for charging.

*Some other factors: For example, if the charging cable is too thin or too long, there exits high internal resistance loss in the charging cable, and the current through charging cable is not enough. Then, the charger can't reach the acceptable max charging current. Besides, if there are dirty particles, rust or serious friction on the adapter or USB port, which leads to big internal resistance. It may also cause low current charging, which leads to longer charging time...