Not possible hardware wise. The only thing you could achieve it, is to get a power source giving stabilized voltage in between 3.3V-4.2V range, and hook it up to battery pads. The only way you can achieve it without such mods, is by shutting down all radios, turning brightness to minimum, etc. Basically, you can't use more than ~ 50 mA, and was usable only in battery hotswap proof-of-concept (which was just that - PoF - as it was more convenient to shut device down for swapping, anyway). /Estel