The voltage is 14.4 volts to 14.8 volts.
Indeed, the maximum charging voltage of lithium batteries is generally limited to around 4.2 volts per battery. The 12V lithium battery is made up of several batteries connected in series and therefore the charging voltage is increased from 14.4 volts to 14.8 volts. The charging voltage range aims to ensure a balanced state of charge for each battery and to avoid exceeding the maximum charging voltage of a single battery.