It's summer. The sun is popping. So right with force. And in my household, there's a very educational experiment right now about what happens when you tell a teenager that electronics don't like heat. Spoilers: The experiment is not going well.
But from the front.
The purchase
Two weeks ago, it had to be an iPhone 13. It's cheap. It's used. Because without an iPhone, you're only half a person, every 15-year-old knows that. Well, yeah.
On closer inspection, the device in question had a history that could actually have been read as a warning signal: No original display, no original battery. So exchange parts of unknown origin and goodness. And, the icing on the cake: somewhere in its turbulent past, the device had decided Becoming a Baptist, When she got acquainted with a toilet.
However, the purchase took place. If you don't have an iPhone, you're only half a person. (says the puberty)
Well, yeah.
The current state
The device randomly boots into a recovery loop and feels like it's cooking an espresso. Not ideal.
And here comes the instructive part, because that's no coincidence. Heise sums it up nicely: Smartphones and tablets can only passively dissipate their heat inside via their housing. If the ambient air is very warm, this cooling will no longer work. To avoid damage, the processors throttle beyond about 35 degrees, e.g. the clock rate, the performance decreases.
That sounds like a controlled, benign process. Ordinarily it is. But our patient here is not a normal case.
Why this is different
An original battery in a neat iPhone 13 copes with heat. A third-party battery of unknown origin in a device with water damage history is another thing. The feel-good temperature of batteries is between about 10 and not quite 30 degrees. When exposed to high loads in a very warm environment, the battery temperature quickly exceeds this range. If it reaches more than 50 degrees, many devices switch off with a warning or at least block access.
A random recovery boot loop on a device that feels hot and has a spare battery? This sounds strongly like a battery that delivers unstable voltages under stress and then forces the iOS to its knees. Recovery loop is often just that: the firmware notices that something is wrong with the power supply and does not come up any more.
The water damage issue doesn't make it any better. In the worst case, condensation leads to a short circuit on the board. Many manufacturers then flat-rate refuse the repair under warranty because they assume a water damage. In a device that has already had water damage, heat cycles can reactivate old corrosion damage on the board that was inconspicuous in everyday life.
What can you do now? …, of course.
Basically, of course, the following: If a smartphone has been exposed to too much heat: Take it out of the direct sun, remove the phone case, turn it off. If a fan is nearby, place the smartphone in the airflow. Lay on a cooler surface so that the heat escapes better, cool metal surfaces in the shade transport the heat away faster.
What not to do: Put an overheated smartphone in the refrigerator. This may result in condensation inside the device, whether with a waterproof housing or without. In the worst case, condensation leads to a short circuit on the board.
With our special candidate here, I would let the device cool down completely and then see if it boots stable. If the recovery loop continues at room temperature, the replacement battery is the most likely candidate and would need to be replaced again. This time ideally with a component that can withstand any quality control.
The real conclusion
Heat is a stressor for every smartphone. For a healthy, original device, this is usually not a drama. For an iPhone 13 with a third-party battery, third-party display, and a water damage history, summer is basically a survival test.
TL:DR
The device just didn't pass it. 🙁
By the way, the 15-year-old finds this incredibly unfair. The phone worked for the first day. And it was cheap. This is true, but ‘has worked before’ is not soooo resilient in the case of used equipment with the history of this specimen. Okay, it worked! Until now.
Well, yeah.