I have not had any problems with the issue of which you speak, that if I load floor every night, but almost always stay at home and have not seen a drop in battery of these, so if I can say from experience is that the 5 GHz band gives a lot lower than 2.4 coverage, I think with a smaller mobile coverage will consume more, in every way for your case always connect to 2.4.
Diferencialas networks and rename, delete the 5GHz on mobile and leave the setting alone to 2.4 GHz.
To all this I use the 5 GHz. on the phone but I made sure that I have coverage throughout the house.