The recharge time in hours equals the battery capacity in Ah, multiplied in the depth of discharge in %, multiplied by 0.8, multiplied by 1.5, divided by 100 times the charger current rating in Amps, plus one hour. For example, a 55Ah battery, discharged to 80%, on a 6-Amp charger, which would take about 9.8 hours. The battery should reach 80% recharge relatively quickly, while the last 20% is done in constant voltage mode, and will require more time. Our chargers indicate when a battery has reached 80% charge, with either an LED marked 80% charge or a flashing charge light. At the end of the charge cycle, a green ready LED will show that the battery is ready for use.