WF-139 Charger ?


Jan 13, 2010
I have a couple of these and they have worked out fine. I have checked my batterys after the light turns green and they seem to stay at the voltage when the red light turned off. Even after forgetting and leaving batterys in charger overnight no over charging problems.
I mainly use IMR cells in 16340 - 18500 - 18650 - 26500 and all seem to end up at 4.16 - 4.18 volts no matter how long left in. I have never had a ending volts reading of higher than 4.18.
Sometimes after using a two cell light one battery will finish charging in 30 minutes and the second 2 hours? In a three cell maybe two will be done in 1 hours and the 3rd taking an additional hour. Ending voltages of all cells are the same. Batterys are fairly new and have never been run down low. What would cause this big charge time difference between batterys of the same age - entering the charger at the same voltage - ending up at the same?


Flashlight Enthusiast
Feb 15, 2009
Melbourne - Australia
1st / Which charger does what ?

In multi battery set ups , which battery takes longer ?

Lets say the battery closest to the head is 1 and furthest is 2 or 3 ...
Have you established which batt does what ..

Or which charger does what ?

You question is vague and offers multiple answers ...

You cant ascertain this by using multiple chargers / bays , because you will be introducing variables , if you want to investigate this , chose one charger , one bay , take the resting voltage of the battery [ make sure there all the same ] , lets say 3.5v , and time the charge .

Another variable to consider is the internal resistance of each cell , as this will affect charge time as well .

You would really want to investigate each cell [ discharge capability for example ] to see how closely matched they are .

Just because there the same brand/type/capacity does not mean they perform the same , have the same discharge rate , charge rate , or even true capacity .

:thinking: You may chose to be blissfully ignorant , or open a can of worms .



Flashlight Enthusiast
Jan 12, 2006
Died Nov. 2015

You need to learn more about the SAFE use of multiple cells in lights , and matching of cells .

Both in use and while charging. :)

And about variation of internal resistance in cells . :D

Please be safe . :tinfoil:

This "Sticky Thread" at the top of the batteries Forum has a lot of good reading material .

Last edited: