Battery Work, But can't be charged - Possibility Grounding Issue

Hi,

so i actually accidently broke my iPhone 4 battery connector, it ripped off from the board,

but since all soldering pad was still there so i ask someone more experienced in soldering to re-solder it back,

we plugged the battery, the phone boot up without problem. Plugged the cable, it vibrated and show it charging.

But now, the problem is, it not actually charged, the screen show it's charging but the battery capacity never going up, only draining... i don't know where the electricity goes to...

so i open back the phone, and i noticed that the soldering on 2 pins from the right side (this position is if you hold the phone with camera position at bottom left) is actually touch each other. And the wifi grounding plate that was supposed to screwed together with battery isn't there.

Now my question is :

'''1. What actually this 2 pins do? Grounding things? is the charging problem come because this 2 pins touch each other? Since no short circuit happen, i don't think this 2 pins have any related thing with +/- pole.

2. I actually tried to put back the wifi grounding plate on it's place. But the funny thing is that the phone won't boot up with the plate installed. But once i removed it. It boot up, but still charging problem won't go. Why is this? Also grounding problem?'''

As for now, my phone died because run out of juice. And i plan to repair the soldering so the two pins won't touch each other anymore.

But i really curious and want to know what this problem is all about? Is it simply grounding problem? Or any more complex thing? (i hope not)

Will be very happy if you guys can enlighten me here.. :) -- been googled it down for two days, only to get reference about the grounding plate but i need more info on this.

Thx!