But a fifteen minute stop is sufficient. can you recharge in that time?
Yes, of course. You can charge in 2 minutes, but you won't add much. Point is - you don't have to fill it. You only need what you need. Any extra is a bonus.
You give it the shorter of
- time it takes to add what you need until your next opportunity
- time it takes you to do your parallel activity.
Charging speed depends on far too many factors. And the "value" of that charge depends on the vehicle's efficiency. The Ioniq5 for example can go from 10-80% full in under 20 minutes at the right charger. That represents around 200 miles added real-world.
There is a different way of thinking here. Suppose that on that initial 250 mile journey to your 15 minute R&R stop, you also stopped elsewhere for another reason. If you had plugged it in (even if not close to being needed) then, you'd have added some range and thereby possibly shortened the next stop. Think ABC (Always Be Charging) for best use of your time.