[caption id="attachment_7190" align="alignleft" width="532"]Power drain Red rectangle marks the problematic hot area.[/caption]

I've been pleasantly surprised at how far I was able to revive a Nexus 5X soaked in a public swimming pool for 30 minutes, but I think I've reached my limit.

All the phone functions I tested had worked, but using the phone for more than an hour uncovered a serious problem: something related to battery power management is very ill.

The first symptom was heat: the phone got far hotter than it used to, and trying to run the phone while plugged in to the charger resulted in a lot of heat and not a lot of increase in charge level.

I shut the phone down, unplugged it, and set it aside to wait for it to cool. It remained warm for many hours and never cooled. When I turned the phone back on briefly to check, I see the battery charge level has dropped dramatically. Something was draining battery power and turning it into heat even when the phone was turned off.

I knew most phones had two charging programs: One while the phone is on, running under the main operating system. And a second while the phone is off, run by a very minimal piece of code. I've already tried the first without success, so I turned off the phone and tried the second. Fortunately this was able to charge the battery though the phone still got pretty toasty.

After the battery was charged again, I disconnected the battery. Only then was the phone able to cool off. When I reconnected the battery, it was quickly obvious the heat source is under one of the pieces of metal shielding, marked in the picture by a red rectangle. I don't know how to remove that metal shield without destroying the components underneath.

Two hypothesis are open: (1) this circuit was damaged earlier trying to run a ruined battery, or (2) the shield isn't as watertight as it looks: there's a lot of pool water chemicals in there corroding parts. Either way, it is beyond my current ability to address, so I have to stop here.

I can't use this as a phone for more than an hour or two on battery. And I can't store it with the battery connected because of the drain. So I'm going to disconnect the battery and put it aside in the hope I'll have better ideas later.