I am thinking of a project where i make a phone out of one of these. But i would like a bigger battery, can i just combine 2 bigger li-polymeer batteries so i still have 7.4V.
Also is it possible to use the sim card slot for cellar uses aswell? I think it might be possible if i use an other 4G module. Otherwhile i will use an external SIM reader like those you use on arduino i guess.
Are my thoughts correct or am i a complete idiot?