after changing battery phone heats up and will not turn on

Hi Mark,

What was the procedure for replacing the battery that was included with the battery? Did you remove the screen connections or leave them connected during the replacement?

Did you have any trouble getting the battery out? I know I killed an iPhone X using a metal spudger that tore the battery cover and caused a spark; anything like that happen during your replacement?

Have you verified the battery connector is fully inserted and locked in place? That's probably the first thing to check; unplug it and use a magnifying glass and a bright light to check the pins on the battery connectors, both on the logic board and the cable. Bent pins can sometimes be straightened with fine tip tweezers, but broken ones can be a big problem. Clean both connectors with 90% or higher concentration isopropyl alcohol and reconnect to see if it makes any difference.

If not, try reconnecting the old battery and see if anything changes.

Give those things a try and let us know what you find.