Setup: 4s 12-206Ah SOK LFPs. wired in series for 48V on an off-grid solar setup. History: Used first in summer 2022, worked great. Batteries disconnected from system over winter. Status: Spring 2023 individually charged each of 3 of the batteries full with the Victron BlueSmart 12V/15A IP65 charger Problem: 1 of the batteries will not charge. While disconnected it reads at about 6.2V. When initially connected the charger reads about 7V/15A (via BT app) during "Test" phase but after a few seconds goes to "Absorbtion" at 14.4V/0.0A. I've repeated this several times with the same result. Is there more I can do to wake-up this battery?

I have 4 new 206Ah batteries in series for 48V. I'm using a Victron SmartSolar 250/85 charge controller, with the "Smart Lithium (LiFePo4)" battery settings: Abs 56.80V, Float 54.00V. They do not appear to charge fully. The charge controller charged them in "Bulk" from 45.0V this morning (starting at about 20A from 5@325W panels) until it held it in Absorption at about 56.8 or 56.9 with 0A charge current. But when I turn off the charge controller the battery voltage drops to about 51.8V. Further, by then putting them under load with 30A the voltage will hang at around 51.2V initially. Under this same load last night the batteries gave 30A for a few hours before the inverter shut off at 45V. So: The voltages come up to 56.8 where the CC thinks they are full and stops charge current, but they are not charged. How can I debug the issue?