A:Answer Every device should have a capacity rating for the battery in mAh. The iphone SE first gen has a 1642 mAh battery. The 20,000 mAh version of this battery pack should be able to charge your iphone SE about 12 times. Taking into account energy transfer inefficiencies with different cord types/lengths and heat generation, maybe a little less at 11 full charges.
On the flip side, you might want to get your SE's battery changed out sooner or later.