How to Calculate the Battery Charging Time & Battery Charging Current – Example

How to Calculate the Charging Time and Charging Current for Battery Charging?

Easy Battery Charging Time and Battery Charging Current Formula for Batteries. (With Example of 120Ah Battery).

Below is a simple battery charging current and battery charging time formulas with a solved example of 120Ah lead acid battery.

Here is the formula of charging time of a lead acid battery.

Charging time of battery = Battery Ah / Charging Current

T = Ah / A

Where,

T = Time hrs.

Ah = Ampere Hour rating of battery

A = Current in Amperes

Related Post: Difference Between a Battery and a Capacitor

Example:

Suppose for 120 Ah battery:

First of all, we will calculate charging current for 120 Ah battery. As we know that charging current should be 10% of the Ah rating of battery.

Therefore,

Charging current for 120Ah Battery = 120 Ah x (10/100) = 12 Amperes.

But due to some losses, we may take 12-14 Amperes for batteries charging purpose instead of 12 Amp.

Suppose we took 13 Amp for charging purpose,

then,

Charging time for 120Ah battery = 120 / 13 = 9.23 Hrs.

But this was an ideal case…

Practically, it has been noted that 40% of losses occurs in case of battery charging.

Then 120 x (40 / 100) = 48 …..(120Ah x 40% of losses)

Therefore, 120 + 48 = 168 Ah ( 120 Ah + Losses)

Now Charging Time of battery = Ah / Charging Current

Putting the values;

168 / 13 = 12.92 or 13 Hrs ( in real case)

Therefore, an 120Ah battery would take 13 Hrs to fully charge in case of the required 13A charging current.

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