How Long Does It Take to Charge a Battery Using a Rectified AC Supply?

[kurt13]

Homework Statement

Hello,

I have one hard exercise, that I can't do. Sorry for my English, it's not my mother tongue, but maybe somebody could help.

To charge a battery with direct current I, it takes t=8 h. But they didn't have a DC supply, so they charged it with AC, that was rectified with full-wave rectifier. The electro-dynamic system ammeter is plugged into the battery charging circuit and shows exactly the same I, like when charging with DC. So I1=I2. How long it takes to charge the battery with these conditions?

I now the answer, which is t1=8,8 h, but don't now how to get it. :)

So I hope that someone can help me.

I got some hints from professor, so I attach them also in here.

Homework Equations

The Attempt at a Solution

 

[kurt13]

Does anyone know how to do it or can give me more hints ?
I would be very thankful, I kinda need this pretty soon.

And when integrating, what should be tracks? [1) 0 ... Pi or 2) 0 ... t)]