Answer to: iPhone 4 Battery replacement - two "bad" batteries?Check the batteryconnector. The 2 tabs on the batteryconnector must match the grooves on the phone 100%. Miss this little bit and the phone will get power from the battery, but won't charge.
Answer to: Battery iPhone 4s doesn't charge at allon the iPhone 4 check that the 2 tabs on the battery connector line up perfectly with the grooves on the phone. I missed this and my battery did not charge. When corrected all was good.