I can confirm the app causes 3DS/2DS to crash if we try to exit the app after finishing the test(Might have something to do with attempting to upload the results and failing...)
Also just got a new battery for my New 2DS XL, taking it apart was a giant pain, ending up with small crack in one corner of the shell, and broken microSD card because I forgot to take it out and somehow it got pulled out when I was putting it back together... but either way final result of new battery(Allegedly legit Nintendo one and new... though I doubt it was really "new", probably taken out of like a broken pro controller or something) looked like this:
Battery time max: 00:03:50.1
Battery time avg: 00:01:46.9
Battery time min: 00:00:37.3
Total Elapsed time: 02:40:23.4
Meanwhile I tested once with old battery before that too and result was:
Battery time max: 00:03:03.3
Battery time avg: 00:01:43.1
Battery time min: 00:00:49.2
Total Elapsed time: 02:34:41.4
Nothing quite like almost breaking my console for extra 6 minutes XD