How long to charge 48v LED batteries

[Rockten]

I recently bought six (off the shelf) 8V rechargeble led batteries from 2019 at a discount from a local shop who did not have newer batteries. I even got a 3 month guarantee from the shop. These 6 batteries are manufactured by DEKA and 8148EX (GC8V) batteries and the manufacturer informed me via mail that each 8V battery is fully charged when it reaches 9.6V per 8v battery which equals 57.8V for all 6 batteries.

I also bought a new Lester Series II OBC bypass charger on the internet to charge these batteries. However I have been charging the batteries for more than 12 hours and is still not fully charged. Is this normal? Or is this a sign that these 2019 batteries are damaged?

When I plugged the charger yeaterday, the charger read 47V and reported 0% charge and more than 1200 charging minutes remaining. This represents 20+ hours of charging. I attached a picture of the bluetooth connection of the Lester charger when it reached 3% (maybe an hour later) that showed something similar. Is this normal?

I decided to leave the batteries charging the whole night and this morning the charger is reporting a 86% charge at 58 volts but still 300+ charging minutes (5 hours) remaining. I also attached a screenshot of this report. Is this normal?

I need to know if this is normal or if I should return the 2019 batteries.

Thanks in advance for your replies.