Re: is there any way to calculate how many amperes battery provide?

In short, no! The current will depend on the internal resistance of the battery, which is a characteristic of te battery type, state of charge and other factors such as temperature. It is not possible to determine the charge remaining in the battery from the terminal voltage, as the voltage/time curve is very non-linear. Modern rechargeable battery systems determine remaining battery life by continuously measuring the amount of charge which has gone into or out of the battery.