A 10 amp charger can charge a 50% discharged small car battery (200-315 CCA or RC 40-60) in about 2 to 3 hours, a mid-sized battery (315-550 CCA or RC 60-85) in 3 to 4 hours, or a large car battery (550-1,000 CCA or RC 85-190) in 4 to 7 hours. Double these times if the battery is fully discharged.