From a Battery University article:
"Increasing the charge current does not hasten the full-charge state by much. Although the battery reaches the voltage peak quicker, the saturation charge will take longer accordingly. With higher current, Stage 1 is shorter but the saturation during Stage 2 will take longer. A high current charge will, however, quickly fill the battery to about 70 percent"
https://batteryuniversity.com/learn/article/charging_lithium_ion_batteriesHas the sort of graph I want for 1C. Note the Absorption Stage time! Where is that 15 minutes ?
(next I will be scolded that not all Lithium -ions are the same, so that graph doesn't count---so find a link to a real LFP one please)
EDIT the idea that Bulk is shorter with higher charge rate is the same as with FLAs but to a different degree of course.
Here is another quite from someone with LFPs who seems to have a clue base on other posts . They work their LFPs hard cycling 5%-95%
"Charging LiFePO4 is a two step process … FIRST step uses constant current (CC) to reach about 60% State of Charge (SOC); And then STEP 2 kicks in until the charge voltage reaches 3.65V per cell. Turning from constant current (CC) to constant voltage (CV) means that the charge current is limited by what the battery will accept at that voltage, so the charging current tapers down asymptotically.
If you had to time the process – STEP ONE (60% SOC) needs about one hour and the STEP 2 (40% SOC) needs another two hours .. I have seen it that way ever since I started working with LiFePO4"
