Could be any number of things from the charger not being USB-C PD to the sun overheating your phone and causing the safeties to stop or slow down the charging. I haven’t actually found a car charger with a buckboost converter in it to provide higher voltages even when the circuit board is available online for hobby projects.
“USB Battery is very large, but takes very long to charge all the way.” on a battery that supports both USB-Micro and USB-C Fast Charging.
Fast charging refuses to work in my car 👎
Could be any number of things from the charger not being USB-C PD to the sun overheating your phone and causing the safeties to stop or slow down the charging. I haven’t actually found a car charger with a buckboost converter in it to provide higher voltages even when the circuit board is available online for hobby projects.