Battery Charging Current and Battery Charging Time formula

Here is the formula of Charging Time of a Lead acid battery. 
Charging Time of battery = Battery Ah / Charging Current
 T = Ah / A

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.
so charging current for120Ah Battery = 120 x (10/100) = 12 Amperes.
but due to losses, we can take 12-14Amperes for charging purpose.
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, this is noted that  40% of losses ( 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 
168 / 13 = 12.92 or 13 Hrs ( in real case)

Therefore, an 120Ah battery would take 13 Hrs for completely charging ( with 13A charging current).