I’m afraid thart you cannot calculate the power of the generator with the capacity of the battery.

Power of the generator is a rated parameter.

The battery capcity is another rate figure for another component (the battery).

In fact, with the battery capacity AND the power ratign of the generator what you can calculate is tje time for the generator to fillthe battery.

Example:

Let’s assume 3V rated generator (for easiness) and a 3V/300mA*h battery.*

If the amps rate of the generator is 100mA, it will take 300mAh/100mA = 3.0H charging time.

If the amps rate of the generator is 300mA, it will take 300mA*h/300mA = 1.0H charging time.*

If the amps rate of the generator is 600mA, it will take 300mAh/600mA = 0.5H charging time.

I would like to konow the same rated figure for the hydro-generator.

The power capacity at different at different turn rates

Is any how we can know it?

It would be very useful.