Question about Varta plug charger

Nothing is actually written on the batteries about the charging time - but I know that they get warm when charging. As far as the devices are concerned - yellow plug green light goes out when full - white plug blue light goes out when full - only charge in pairs! I use the 2100 mha varta for kitchen clock and dental soap dispenser since 1998 every 3 years 1 x exchange
Runs !

that doesn't work for me either. you can't rely on the lights. charging over night should certainly be enough...