A:Answer Most portable charger brands recommend against this. You can charge your phone or the portable battery, but you are not supposed to have the portable being charged by the wall outlet, while simultaneously having the portable charge your phone.
I found that while traveling, carrying a "splitter" helps. Meaning, turning one wall outlet into two or more. Just a smaller version than your strip outlets you likely use at home.
Most hotels, if modernized, have ample plugs and USB ports.