After replacing the battery, phone wont hold a charge-what is problem?

after replacing the battery, the phone would no longer power up or respond to any button pushing.

i tried soft reset, hard reset, plugging it into the computer, letting it charge... everything. the phone is still an expensive paperweight.

the only response i can get from my phone is when plugged into a wall outlet. when i press the power button, the apple appears for about 15 seconds and then goes black. after going black, you can see where the screen appears to be on for just another second or two (like a screen burn on old tvs) and then it goes completely black (like the phone is off)

Please help