Will charging my iPhone 4S with iPad 4th generation 12w power adapter, ruin my battery?

Situation: my iPhone 4S is 4 months old, have had ZERO issues with battery life, until yesterday...

I just bought the newest iPad last week (retina display) and yesterday I plugged the iPhone 4s usb cable into the iPad 12w power adapter, to charge my 4s. Now my iPhone 4S is losing 1% every 4-5 minutes (not exaggerating, in fact it may be draining even faster than that). This is occurring even though all programs are closed and the phone is locked (screen is black)... Normally my battery will lose 5-10% while I sleep, last night it was dead within 5 hours !

I'm pretty disappointed becuz it seems I have ruined the battery. Can anyone think of any other reason for this to be happening?

In an attempt to rule out any software issues or potential malware, I backed up my 4s, put it in recovery mode and proceeded with a factory restore. Following that I restored from backup. To my dismay the freefall battery drainage is continuing :(

What are my options (if any) apart from heading over to apple store tomorrow to get bent over a barrel? Any help would be appreciated ....

Many thanks and happy holidays !