Just to clarify, are both Galaxy S5 phones? You refer to a 'replacement phone' but is the replacement also a S5 or a different model?

 

How did your charging port go bad? Have you tried cleaning it?




I have several Note 4's o er the years. I also had the same experience doing the swap batterys back and forth. I have no idea why the same battery booted on N4 and didn't boot the other, although sometines it did. Weird Right? Anyway, I cleaned the loose usb port with a thin plastic pick. Small enough not to push the center part of the phone usb port (moves freely). Afterwards, I could pug in the phone and slightly hold the charging cable a certain way until it showed a charge. When it did I could successfully power on my N4 with the battery that previously did not boot the phone.

 

The major difference between your two S5s will primarily be the motherboard inside. Back when the S5 was in its day, T-Mobile used (and uses) a GSM-based cellular network and Sprint primarily relied upon a CDMA-based cellular network.
https://www.pcmag.com/news/cdma-vs-gsm-whats-the-difference
That's thankfully all becoming just history as the carriers have moved on to LTE and (upcoming) 5G (... and T-Mobile has recently bought out Sprint anyway), so differences in the two phones will be mostly things like the cellular radio and antenna controller chips on the main firmware board. But there are not separate Galaxy S5 batteries for different carriers, they're pretty much universal as far as compatibility. The differences being build-quality, capacity, etc. So that does add to the mystery of the problem you're having, there's a missing piece to the puzzle that is yet to be determined.

As an aside, looking up your phone model on the iFixit site, it does show the charging port is part of a separate daughter-board. If you're comfortable with tearing down your phone, replacing just that daughter-board is relatively less invasive than with a lot of phones where the charging port is soldered directly onto the motherboard.
Their step-by-step guide for this here:
https://www.ifixit.com/Guide/Samsung+Galaxy+S5+Micro-USB+Port+Daughterboard+Replacement/27077

 

Your welcome

If you're able to find a solution to the issues your having please post back with the info. It msy help someone else.

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