Question: How long does it take to recharge a full discharged gel battery? Answer: A specific time is difficult to determine because recharging time depends on so many variables: Depth of discharge Size and efficiency of the charger Temperature Age and condition of the battery Remember that it will take about 60% of the time to bring the battery from 10 1/2 volts to 90% of charge (12.92 volts). It will take the remaining 40% of the charging time to put the last 10% of the charge into the battery. (13.0 volts = 100% charge). For example, if it takes 3 1/2 hours to 90% of charge, it will take approximately 2 1/2 more hours to bring it to full charge. (3 1/2 hrs. to 90%...6 hrs. to 100%)