For example, if you have a single lithium-ion cell that has a max charge voltage of 4.2 volts and a max charge current of 2 amps, you can use those same settings to charge a battery that has 3, 20, or even 100 of those battery cells in parallel. The problem is that it will take a whole lot longer to charge if the current is not increased.
To charge batteries in parallel: Whatever the recommended/max charging current is for a single cell, multiply it by the number of cells in parallel when charging. Make sure the batteries have the same voltage level (probably no more than a 100mV difference). Understand the charging current for each individual cell. Use the exact same cells for charging in parallel.
For charging time, the charging capacity of the parallel battery pack is 20.50 Ah in 1964 s, which is equivalent to charging the battery pack at a constant current of 37.58 A (i.e., 1.25C). In addition, the effect is significantly better than the fast charging of CC-CV of 1C.
In other words, for a parallel battery pack, the initial input total current is the current of a cell multiplied by the number of branches. At the same time, as the charging process goes on, the overpotential will decrease, requiring subsequent control.
The good news is that when charging cells in parallel, the charging current is equally split between each cell. So, if you have 3 cells in parallel and each one of them can take a 2 amp charge current, you will be able to the 3-cell parallel group at 6 amps.
Parallel charging is possible for batteries. You just need to ensure that you use good battery cells and that the batteries being charged in parallel have the same voltage level (probably no more than a 100mV difference).