Battery Management Systems for Large Lithium-Ion Battery Packs
Section 220.127.116.11 Addenda
Saying that the charge efficiency of Li-Ion cells is 100 % is an oversimplification. In reality:
- Internal self discharge (leakage) reduces that efficiency, though in a minor way
- Although close to ideal, the Peukert coefficient of Li-Ion cells is not exactly 1.00; its value is on the order of 1.05
- Due to mechanisms that are not yet understood, there is a phenomenon called "SOC unbalance evolution", which (in the absence of balancing) results in the SOC of weak cells to be reduced, as they are cycled, more than would be expected based on the integral of the charge in and out of them. Though unexplained, this effect is seen experimentally, so it is undeniable.
I will update this section as the understanding on these effects improves.