I’ve been using “pen” style batteries on Kanger tanks for years. I keep a log of juice consumption so I know how the batteries and coils perform. All coils are 1.2 to 1.5 ohms. When a battery drops below a certain level (mils of juice per charge) I discard it. I’ve probably been through 30 to 40 batteries in 10 years.
The last two batteries I bought under performed when new. One was a batch of Kanger 1600 mAh, and one was a batch of Vision Spinner 1600 mAh. I used to get over 2 mils of juice on these brands. The new ones only get 1 mil, sometimes less. I’m confident the batteries are genuine.
Then I noticed that after I charge the batteries and get a green light, if I unplug it and immediately plug it back in I get a red light again and more charging for several minutes. I have a USB power monitor, a unit that inserts between the device being charged and the charger and shows the volts and amps being used. On this second charging the monitor shows the same 5.00 volts and 0.25 amps as the first charge.
Strangely, this second charge behavior does not happen on older batteries. Only the new ones I got in the past 6 months. Older batteries stay green on second charging. I’ve moved the batteries to different connectors and different power bricks with no change.
So I have a mystery. The Kanger and Vision batteries were bought 2 months apart from different vendors. So, I’m wondering if something has changed in battery manufacture or the material (Lithium) used. It appears my newer batteries begin to self-discharge immediately after disconnecting from a charger. When I charge batteries, they usually sit unused for a week or two. That might account for the variance in performance on the newer ones, but I’ve never seen that on older ones.