Li Ion Battery Charging - Initial Results for Float Charging New LiIon Cell

Background and Method

The initial testing I undertook revealed where the shortcomings in my approach were. To bring more rigor to the testing I have started a trial as follows:

Take a pair of brand new batteries. One, let's denote it as x1, will be subject to the CC/CV regime at around 3.9V. The second, say x2, will serve as a reference. The capacity of x1 and x2 will be initially tested fully charged. 

I then put x1 in my CC/CV charger and left there until the capacity is tested, about fortnightly. After testing  x1 goes back into the CC/CV charger.

Meanwhile, after testing x2 will be charged to 3.6 volts before removal from the charger and stored. Every 6 months it will be then fully charged and tested before re-charging to 3.6 volts and storage.

Capacity testing will be by discharge to 3.0 volts. 

 

Initial Test Results after Two Months

Having established a base line for the cell capacity when fully charged I have now floated one cell at 3.9V for two months with 4 discharge tests during that period. After the third test where I had minor contact resistance issues I soldered a connector onto the cell for discharge testing for the fourth and onward tests.

I am yet to see any meaningful degradation in capacity when floating at 3.9V. I will do a full charge/discharge test for both the floated cell and the stored reference cell next month.