Yes, if you're adding more current to the battery than you remove, it will charge.

But if this current is coming from a windmill that is being powered by the bike itself, which is powered by a motor powered by the battery ... your windmill will slow the bike, which will put more load on the battery than it will add to the battery. The laws of physics are not on your side here.

Now, if the windmill is charging the bike while it's parked due to it being a windy day, that's another matter -- but if the wind comes from the motor moving the bike, no, that's not going to work.

Look at it this way ... if this worked, why don't cars have air turbines on top? If we could make an electric car that charged itself while it was driving so it only needed a small battery to go hundreds of miles, we would, and everybody would be driving one because they'd never need gas or charging. But the laws of physics don't work that way.