After battery replacement, I still get the "ping" ever 20 seconds.

I replaced my iPhone 4S battery from iFixit per video instructions. All went very well until I put the phone back into service. It returned to the 20-second interval of pings and failed to reboot. After about 10 mins of this, the phone became very warm. I unplugged the power and let it cool down. I repeated this again and I got the same results. Nothing I do seems to help - holding the on/off button and the screen select button simultaneously for 30 sec doesn't force a reboot. I'm back to the same condition of this phone prior to battery replacement. Another video suggested checking connections - I did this too making certain that all cable connections in the phone are securely seated. Nothing was found to be loose. So, can anyone help with suggestions on what to try next?