It's worth noting here that *ALL* Lithium-Ion charging methods slow down at 80%. Lithium based batteries charge in 2 phases called CC (Constant Current) and CV (Constant Voltage.)
In the first phase the charge controller supplies the battery with a constant amount of current and lets the voltage rise to the specified voltage. For most Lithium-Ion/Polymer batteries this will be about 4.2V/cell max voltage. Some can get up to 4.35V. At the end of this phase the battery is at max voltage, but is around 80% charged, although this can vary.
When the battery hits max voltage, the charge controller switches to CV mode, where it supplies a constant voltage and lets the current taper off until a specified charge current is reached, at which point the charge is terminated.
For systems where you can set the desired to charge to some % of max, what you are doing is altering the final charge voltage on the CC-CV switch.
In the first phase the charge controller supplies the battery with a constant amount of current and lets the voltage rise to the specified voltage. For most Lithium-Ion/Polymer batteries this will be about 4.2V/cell max voltage. Some can get up to 4.35V. At the end of this phase the battery is at max voltage, but is around 80% charged, although this can vary.
When the battery hits max voltage, the charge controller switches to CV mode, where it supplies a constant voltage and lets the current taper off until a specified charge current is reached, at which point the charge is terminated.
For systems where you can set the desired to charge to some % of max, what you are doing is altering the final charge voltage on the CC-CV switch.