Yeah, with MagSafe 25% of energy is wasted as heat (takes 20 watt but delivering only 15 to phone). 20 watt is almost at limit how fast 13 can charge (22watt max I think), and 5 watt (5V at 1A) charger is super slow in comparison. That’s why in my original comment I said specifically that if you use that charger you’ll be good. How long does it take to fully charge? Must be 4h at minimum?

What was the temperature difference?

30C feels warm to the touch but it’s nothing for battery.

It’s not always that clear, charging with 5V requires more amps and that will lead to components heating up. So you may no be doing any favours to your battery by charging with slower brick (unless it’s one of those 5V 1A brick)

I had flir picture of power bank with charging chip running at 110C/230F charging at 5V 2.5A, can’t find it though, probably deleted.

There’s a reason why electricity from power plants is transferred at up to 1.000.000 Volt.

“The USB PD PPS (programmable power supply) technology determines the charging status of a battery in real-time, adjusting the voltage and current to deliver maximum power while minimizing the temperature rise.

Qualcomm’s Quick Charge technology has evolved with a focus on temperature management. Quick Charge 2.0 added Dual Charge, which uses two power-management ICs (PMICs) in the handset to split the charging current into two streams. This reduces handset and, therefore, a rise in battery temperature.

…

Quick Charge 3.0 without Dual Charge+ is up to 6° C cooler, 16% faster, and 38% more efficient than Quick Charge 2.0, and Quick Charge 3.0 using Dual Charge+ is up to 8° C cooler, 27% faster and 45% more efficient than Quick Charge 2.0 with Dual Charge.”

https://www.batterypowertips.com/how-fast-can-li-on-batteries-be-charged/

That’s not how optimised battery charging works, it should charge at full speed to 80% and then wait. It wouldn’t make sense otherwise, you may want to charge your phone before going for night out and phone wouldn’t charge?

“With iOS 13 and later, Optimised Battery Charging is designed to reduce the wear on your battery and improve its lifespan by reducing the time your iPhone spends fully charged. When the feature is enabled, your iPhone will delay charging past 80% in certain situations.”

https://support.apple.com/en-gb/HT210512

My bet would be on damaged cable or socket full of pocket lint.

Did you actually read their privacy policy? They will hold on to your email only temporarily when you use “send later” feature - for obvious reasons.

Never heard of email client using own servers to hold users emails, it doesn’t make sense, server space is not free and they already have access to all your emails.