I think my Switch might be draining power too quick

I was on a trip, and decided to play Breath of The Wild, as Nintendo claimed that even on max settings you were supposed to get to about 2 and a half hours. A little less than an hour later I was at 50% battery on LOWEST brightness and airplane mode. I've never dropped my Switch, so I can't think of anything that could have made the battery bad. I just got my Switch on July 21st. Do I have to return the console, because I really do not want to restart the progress in all my games (BOTW, Snipperclips, NBA Playgrounds). Is there something I'm doing wrong? Is it displaying my percentage wrong? I need help.