How does the X4 charger discharge a Li-ion battery when not powered?

XTAR Light

Apr 26, 2010
A customer left one fully charged 18650 battery unused in the X4 charger for 3 days. He noticed the battery charge volume dropped around to 60%-80% on the charger. Why the battery was discharged so badly? Was the charger or the battery broken? Let's check more below.

When the X4 charger is not powered, put the fully-charged 4.2V Li-ion batteries into its CH1-CH3 slots, the standby current is around 7mA. After 20 seconds, the microcontroller enters the sleep mode, reducing the current to around 0.5mA. It's not a continuous discharge and should not cause the battery charge volume drop to 60%-80%. If the batteries are placed in CH1-CH3 slots and left for three days, the cumulative power consumed by the charger would be around 36mAh, which is not a significant amount when considering individual batteries. The discharge rate is within normal range. As for the CH4 slot, it has a 5V USB output function. When not powered, insert a battery into this slot, the USB output and the LCD screen lights up, the idle power consumption is around 59mA, and it reduces to 15mA after the screen is turned off. The standby current in this slot is considered reasonable.

We test some batteries in the X4. When the battery voltage is below 4.13V, it shows 60% charge on the screen, and at 4.15V, it shows 80% charge. If the battery is not of high quality, after being fully charged and left unused for three days, its voltage may drop to 4.13V. Normally, a battery with no load should have a voltage of 4.15V when fully charged. As the charger shows the percentage of the charge volume with 20%, 60%, 80%, 100%, and it doesn't show the accurate percentage like 98%, 99%. The issue may lie in the inaccuracies of the battery charge level display. If this customer's 18650 battery with charge 96%, the charger might show at 80%. So the battery is not actually discharge as much as showed. To get the actual voltage of the battery, the customers can use a multi-meter for testing accurate data.

Besides, one thing to notice, the chargers are designed for charging batteries and not suitable for battery storage. So please store and maintain your batteries properly.


Flashlight Enthusiast
Mar 28, 2013
New Mexico, USA
Interesting and informative. Back when member HKJ was more active, he did find a charger to have a significant drain on batteries left in turned off battery chargers.

Always a good idea to remove batteries from chargers promptly. Faulty chargers may continue to charge, resulting in a possibly highly negative event.