2. Reading is something like this:

a) 47.4V, 50A

b) 47.3V, 49.4A

..

..

and so on until battery discharges completely in one hour.

3. How to calculate Watt & Watt hour consumed from it over hour

Normally if voltage is same, I calculate by difference of current between two multiply by voltage.

But in this case voltage is also reducing(during discharge) & going up during charge.

How to do the calculations of Watt & Watt/hour in it, should I take average of voltage over period of time & multiply by current difference?