The discharge current would have to be 30A to discharge the battery in 20 hours (600Ah / 20h). To work out the discharge time (the “C-rate”) from the Nominal Capacity and the Discharge current, divide the Nominal Capacity by the Discharge Current. This will give you the C-rate.
With a higher discharge current, of say 40A, the capacity might fall to 400Ah. In other words, by increasing the discharge current by a factor of about 7, the overall capacity of the battery has fallen by 33%. It is very important to look at the capacity of the battery in Ah and the discharge current in A.
There is no generic answer to this. You read the battery datasheet. Either it will tell you the max discharge current, or it will tell you the capacity at a particular discharge rate, probably in the form C/20 where C means the capacity. You know the current you need : 4.61A.
The charging conditions of the battery: charging rate, temperature, cut-off voltage affect the capacity of the battery, thus determining the discharge capacity. Method of determination of battery capacity: Different industries have different test standards according to the working conditions.
Keep the discharge power unchanged, because the voltage of the battery continues to drop during the discharge process, so the current in the constant power discharge continues to rise. Due to the constant power discharge, the time coordinate axis is easily converted into the energy (the product of power and time) coordinate axis.
The discharge current would have to be 400A to discharge the battery in an hour. If the battery has a C20 capacity of 600Ah, it means that when the battery is discharged in 20 hours, it has a capacity of 600Ah. The discharge current would have to be 30A to discharge the battery in 20 hours (600Ah / 20h).