If it is discharged to begin with, AND if it is charged at a specific percentage of C rating... then yes, it CAN have 70% charge when the voltage at the cell reaches 4.2V WHILE current is being pumped into it at specified percentage of C to hold that voltage up. Remove it from the charger while at 70% charge, and the float voltage will go down to under 4V, tada.
Keep it at 4.2V at that point with simple CV @4.2V, and it will be fully charged.
And no, there is no practical reason to cut off the CV charge at a specified number of milliamps current, except that if kept there indefinitely (like a laptop that is left plugged in 24/7 for months) it may accelerate cell degradation, and in this specific case there is no practical reason to not simply set CV phase to 4.1V, or whatnot.
As someone previously stated, OP's original plan of using a CC-CV setup was perfectly reasonable.
The voodoo people attribute to Li ion charging....
If you can understand the datasheet, you know exactly why it is described this way and what it means. It is not voodoo. CC-CV. Auto cutoff to prevent cell degradation if left plugged in. And to have a nice little cutoff point so an indicator light can go on. There is no voodoo. If you want voodoo, you have to play with NiMh.
Phase 1: CC - Pump current limited to a reasonable percentage of C... Because simply doing CV limiting to 4.2V will allow a greater current draw than that.
Phase 2: Once 4.2V is reached, duh, you don't want it to go higher. Switch to CV at 4.2V, and the current draw naturally decreases in a curve.
Phase 3: Keeping the cell at 4.2V indefinitely MAY cause cumulative degradation of the cell over time. And c'mon, we need an LED to go off when the cell is done charging.... you gotta call it somewhere. Let's say call it like 20mA for a 1Ah cell.
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