Due to the limitations of the process conditions, lithium-ion battery pack between the cells even after selection, there is always a certain difference, after several charge and discharge cycles or long-term shelvin.
What is a lithium ion battery pack?
The lithium-ion battery pack is composed of multiple single lithium-ion batteries connected in series. Due to the differences in the cells, when the terminal voltage rises inconsistently when charging in series, some cells will be overcharged and some cells will be undercharged.
Whenever possible, using a single string of lithium cells is usually the preferred configuration for a lithium ion battery pack as it is the lowest cost and simplest. However, sometimes it may be necessary to use multiple strings of cells. Here are a few reasons that parallel strings may be necessary:
When the lithium-ion battery pack is produced and stored for a long time, due to the difference in static power consumption of each circuit of the protection board and the different self-discharge rate of each battery cell, the voltage of each string of batteries in the entire battery pack is inconsistent.
How many lithium ion battery cells need to be connected in series?
The details are as follows. The voltage of a single lithium-ion battery cell is low. If 3.2 V LFP cells are adopted, 160 cells need to be connected in series to provide the battery voltage of 512 V DC. The charge and discharge currents (I) of the cells connected in series are the same.
Do lithium-ion cells influence voltage drift in a 168s20p battery pack?
Using this method, the presented study statistically evaluates how experimentally determined parameters of commercial 18650 nickel-rich/SiC lithium-ion cells influence the voltage drift within a 168s20p battery pack throughout its lifetime.
Furthermore, initial variations of the capacity and impedance of state of the art lithium-ion cells play a rather minor role in the utilization of a battery pack, due to a decrease of the relative variance of cell blocks with cells connected in parallel.