People think I'm crazy for ONLY buying phones with externally accessible batteries (and MicroSD slots). There's so many reasons why you would want tool less access to the battery, and very few of why you would not want to. But yes, "battery out conversations or activities" is a fairly big thing.
Even if there is another battery on the phone, which there usually isn't, it'd have to be the same size as the removable battery. There's usually a very tiny battery or capacitor to maintain the clock time, but I haven't bothered looking it up for phones and tablets. It doesn't have enough power to run a cell modem.
Prof was not a very good revolutionary.