Charging the internal battery from an external one loses a lot of energy, battery charging is very far from 100% efficient
A phone might not use enough energy for this to make much of a difference, but you need to build and carry beefier battery banks compared to internal batteries, and I'm not sure whether you'll see a net benifit
Charging the internal battery from an external one loses a lot of energy, battery charging is very far from 100% efficient A phone might not use enough energy for this to make much of a difference, but you need to build and carry beefier battery banks compared to internal batteries, and I'm not sure whether you'll see a net benifit