Charging Time Required

The time required to charge a battery will vary depending upon the following factors:

Reserve Capacity of the Battery - Expressed in minutes, reserve capacity is the amount of time required for a fully charged battery at 80 degrees Farenheit, discharged at a constant rate of 25 amperes, to reach a terminal voltage of
10.5 volts. When completely discharged, a battery with a reserve capacity rating of 180 minutes requires at least twice as much recharging as a completely discharged battery with a reserve capacity rating of 90 minutes. The reserve capacity rating shown on the battery label or in test specification bulletins may be used to estimate the ampere-hours of recharge (average charging amperes multiplied by the hours of charging) that may be required. For example, a 90 minute reserve capacity battery can usually be completely recharged in 9 hours if the charging current flowing into the battery averages 10 amperes (10 X 9 = 90). If the current averages 30 amperes, 3 hours would be sufficient (30 X 3 = 90). The actual current flow will depend on both the condition of the battery and the output capabilities of the charger. Use the average charging current as indicated by the charger ammeter to calculate ampere hours of charge.

Temperature - A longer time will be needed to charge any battery at 0 degrees Farenheit than at 80 degrees Farenheit. When a fast charger is connected to a cold battery, the current accepted by the battery will be very low at first, then in time the battery will accept a higher rate as it warms. For best results, allow cold batteries to warm to room temperature before charging.

Charger Capacity - A charger which can supply only 5 amperes will require a much longer period of charging than a charger that can supply 30 amperes or more. To minimize charging time, maximize the charging current flow by utilizing the highest charger voltage output setting for a 12 volt battery. Use of a "maintenance free" setting offered on some chargers is not necessary when charging Delco Freedom batteries, and should be avoided when another setting of the charger will give a higher voltage output. The most efficient charging will occur when a voltage of at least 16 volts can be attained.

NOTE: Do not use "boost", "jump start" or "crank" settings to charge batteries if charger is equipped with any of these settings.

State of Charge - A completely discharged battery requires more than twice as much charge as a fifty percent discharged battery. Because the electrolyte is nearly pure water and a poor conductor in a completely discharged battery, the current accepted by the battery will be very low at first. The charging current will increase as the acid content in the electrolyte increases.
BATTERY CONDITIONS

Adapters that provide good contact with the battery terminal pads, AC-Delco Part Number ST-1201, GM Part Number 1846855, or equivalent, are preferred for attaching chargers and test equipment to side and top terminal batteries. Clean battery terminals, adapters and charger or test equipment clamps to ensure good, low resistance connections. If the recommended adapters are not available, standard fasteners should not be used except as noted below. Failure to follow these procedures could result in damage to the battery terminals or high resistance connections that will prevent adequate charging current from reaching the battery.

Side Terminal Batteries - Two 3/8" standard thread (16 UNC) bolts (UNPLATED), at least 1.5 inches long and two standard 3/8" nuts (UNPLATED) are required. Using fingers, screw nuts onto bolts, screw bolts (with nuts) into side terminals until they bottom out, then back off one full turn. Do not tighten with wrench or pliers as bolts can be driven through the case. Holding the bolt, tighten the nut until it is against the battery terminal pad. Snug nut with wrench or pliers. Do not overtighten as battery terminals could be damaged. Attach the charger clamps to the nuts. Charging current can then flow through the battery terminal pads.

Top Terminal Batteries - Two 3/8" standard thread (16 UNC) nuts, AC-Delco Part Number 7802, GM Part Number 1892161 or equivalent, are required. Charger clamps must be placed between the nuts and the battery terminal pads to ensure good contact with the lead pads. Snug nuts with wrench or pliers. Do not overtighten as battery terminals could be damaged. Charging current can then flow through the battery terminal pads.

NOTE: Good contact must be maintained between the charger and battery terminal pads to ensure maximum results. Failure to provide good contact increases charging time by approximately one third.