New Ifixit battery won't charge iPhone 4!

New IFixit battery won't recharge! Install went smoothly, phone booted up with around 50% charge on the new battery. Followed the calibration instructions to let it get down below 10% then recharge; however, it suddenly died at 12%. Plugged it in overnight (low battery image comes on screen momentarily when plugged, so I know connection is being made)... but still red battery image this morning.

Help??