How to Calculate the Charge Time of a Battery
- 1). Determine what the battery capacity is in Amp-hours (Ah). Examine the battery for this value, which is typically 45 Ah. Note that the following calculation assumes that the battery is completely depleted and needs a full charge.
- 2). Determine the capacity of the battery charger. Examine the label or other wording on the battery charger to find the capacity. If it's not clearly listed on the device, check the user's manual to find the charger's capacity. For this example, assume the battery charger has a 15 amp capacity.
- 3). Enter the battery capacity and the charger capacity into the following formula: Charging time (hours) equals Battery Capacity (Ah) divided by Charger Capacity (A). Therefore, the charging time for this example is 45 Ah divided by 15 A which equals 3 hours.
Source...