Charge Controller for QI Cell Phone Charger?

I bought two of these chargers on the internet because my phone has trouble with charging via micro usb. The charger works great; when you put the phone on the coil a blue LED on the PCB will light up and then the phone will say it's charging.

My issue is that if I leave the phone on there all night it will over-charge it and eventually the battery will go bad. (I had to replace the battery once.)

What I want to be able to do is put the phone on the pad, fall asleep, and then in the middle of the night I want for it to turn itself off when the phone is at 100% charge.

What I don't know is how to have the charger begin to detect if the phone is charged and to stop trying to charge the phone further. A way to do it might be to write an android application for the phone which sends a bluetooth signal indicating 100% charge and then having an Arduino get that signal and deactivate the charger, but that seems really complicated. I feel like there is probably a simpler way.

Do y'all have any ideas or am I completely nuts?

There is no simple way. Lithium batteries are very finicky and the charger has to carefully monitor the battery voltage and current in order to safely charge it. The charger also has to shut off completely at some point, which depends on the battery characteristics.

It would be better to figure out why the built in usb charger is not working properly.

The charger works by inducing an electromagnetic field in the receiver.

Would the receiver's field be affected by the voltage level in the battery? The charger has two indicator LEDs, it turns the red one off and turns the blue one on when it detects that a phone with a qi receiver coil has been placed on the charger coil. I assume that means the charger is monitoring the field somehow.

If there was a small change in it because the battery voltage kept increasing then would it be possible to exploit that?