Float Charging Li Ion Batteries - Results for New Cell after 12 months

Background and Method

More fully explained in this post but briefly I am using a control battery to confirm if any degradation is due to float charging or simply the passage of time and high ambient temperatures. Apart from the time being tested the test battery remains in a CC/CV charger floating at 3.93V. This charges the cell to approximately 70% of capacity then floats at this voltage. The control cell is charged to about 50% capacity before being removed from the charger and stored on the shelf. When the control battery is tested it is fully charged before the test.

Results after 12 Months

Having established a base line for the cell capacity when fully charged I have now floated one cell at 3.93V for 12 months. During the test period the floating cell has been subject to 22 discharge tests from the float voltage to 3.0V, and a further 5 discharge tests when fully charged.

Looking at the discharge tests of the battery left on float charge at 3.93V there was no meaningful degradation in capacity.

A full charge of the test battery versus the control battery shows no ill-effects after 12 months. While one cell is not a rigorous sample it should make the self-proclaimed experts feel very foolish. But since they confuse trickle charging with float charging, which are two different charging regimes, and never substantiate any of their claims I suspect they are pretty much clueless all of the time.

If you know how to float charge a Li-Ion cell then there is no evidence that a conservative float charge does any damage to the cell.