6126 Power Problem :(

I've had my 6126 since July and it has been the perfect phone for my use

Well, today I went to use it and it was dead

No power at all

I tried pulling the battery, sim card and SD card, but no dice...

Tried powering it up without the battery (not sure if this is possible) and still nothing...

For the past few weeks I've been charging it using a power inverter in my car, so anytime I went for a drive (which is about 10 times daily since I run many errands), I just plugged it in any chance I got...

Is it possible I could've cooked the battery from overcharging or sumthin?

Tested the battery with my voltmeter and came up with 4.12Volts (it has 3.7Volts marked on the back of the battery)

Anyone ever had this problem before?