Samsung Galaxy Note 9 charging but not charging after repair

JaysNexus · June 27, 2023

Hey there, hope you're having a good day!
I definitely had not, but let me give you the situation first:

I own a Samsung Galaxy Note 9 that has been opened up before (Battery replacement). Therefore it was not watertight anymore and I got it liquid damaged. I dried it completely, discovered that some parts of the motherboard were corroded and wrote that off. On a local site for used items I bought a Note 9 that had its front and back glass completely shattered but worked fine all other ways. I took the motherboard and battery of that and put it into my phone, which worked perfectly for an evening, charged perfectly normal for one night and now does not anymore. (Using Ampere) It shows me that its discharging about (-) 200-220 mA, but when plugged in only gains 100-160 mA but stays very consistantly at 150mA for the most. When opening Ampere for the first time, it showed ~600mA, but quickly dropped to the aforementioned values. I use an Anker 25W Dual Port Charger (12,5W per device).
I immediately thought of two things: further corrosion on the old parts (i only replaced the motherboard and the battery) or a mistake on my part putting it together.
While both would be possible, it did work perfectly for a night so..??
Anyway, I replaced the charging port with the one from the "broken" phone i had bought as well as the battery with a brand new one.
Same thing, ~150mA when charging.
What I also noticed was that the wireless charging didn't work since the first repair. I thought the contact pads (no connector, its just Pads pressed onto the MoBo) were corroded from the water too, but I changed the coil and therefore the contact pads to the one from the "broken" phone which also looked very clean and the receiving pins on the mobo were changed with the MoBo anyway. When placing my phone on the wireless charger, it detects it but flashes, meaning it cannot charge.
(Also, while writing this, Ampere showed "cold" (plugged in, but not charging) for a few seconds, but it went back to charging ~450mA and then quickly down to 150-220mA again).
Now, what could be causing this? With some googling, it seems like most Samsung phones like do just stop cahrging, but I have not found a "charging, but not gaining battery percentage"-problem like mine yet.
What could be causing this issue? What more could I try to fix it?
Thank you for your help and time!
-Jonathan from Germany

Edited June 27, 2023 by JaysNexus
typo

JaysNexus · June 28, 2023

After about 8hrs of charging overnight with the phone shut off, it still lost 5% of battery, making me believe the numbers of Ampere are not realistic.
Even better, now the percentage is all over the place - when I got up, it was 65%, then it jumped to 40%, now it's at 1%. All within one hour.
Im thinking of giving up.

JaysNexus · June 28, 2023

After a restart, it at least read its battery percentage right again. Although still not charging.
I did a hard reset of the phone, but that didn't fix it. Cleaning all ports, connectors, pads and whatever also did nothing.
I'm now guessing its a software issue with the charging. Like, the phone gets power, but somehow tells the charger it doesn't need any more so it only charges slowly. But if a hard reset doesn't fix this, I'm completely out of ideas.
I could not find any further info on that either.