Charging
Will using a charging block rated for less that the 20w or 25w fast charging blocks that are sold separately, degrade the long term life of the battery on my iPhone 13?
Question marked as
no it will just not fast charge but normal charge it
even if a charger didn't output the 5watt that iphones minimum use it would not harm the battery just very slow charge or not charge at all
have you read
About the battery and performance of iPhone 11 and later - Apple
and maybe
iPhone Battery and Performance - Apple Support
and Batteries - Maximizing Performance - Apple