Charging Time of Battery = Battery Ah ÷ Charging Current T = Ah ÷ A and Required Charging Current for battery = Battery Ah x 10% A = Ah x 10% Where, T = Time in hrs. Example: Calculate the suitable charging current in Amps and the needed charging time in hrs for a 12V, 120Ah battery. Solution: Battery Charging Current:
The charging current depends directly on the capacity of the battery, all other things being equal. When you read literature about batteries, you will come across C-rate. For example: "The battery was charged at 0.5C ." It's not temperature in Celsius, and it's not capacitance in Farads.
As the battery reaches 85% of its capacity, the charging current is increased significantly. After the target voltage level is achieved, the charging current decreases and the battery gradually gets charged up to 100%.
When a battery is fully charged, the charging current drops to 0.1C. The circuit switches to constant voltage charging mode once the voltage achieves its maximum, charge cut-off voltage. The charging current of the battery steadily lowers down, and the charging rate slows down when the voltage is sustained at charge cut-off voltage.
Charge Time = Battery Capacity (Ah) / Charging Current (A) This formula is a straightforward way to estimate charge time. For instance, if you have a battery capacity of 50 Ah and a charger that provides 10A, the battery would theoretically take 5 hours to charge. However, this doesn’t account for inefficiencies in the battery charging process.
The maximum charging current for a 100 Ah, 12V lithium battery is around 20 Amps as a general rule.