Reading the comments to dcrainmaker's review, his kids' Bounces were getting 36 hours of charge whereas several commenters state they were barely getting 10 hours, certainly less than 24 hours of charge.

Seems like the energy used to keep the LTE connection up is the main problem, if all the users have the similar settings to minimize battery used by the Garmin Bounce.

If Google/Fitbit says the ACE LTE only lasts 16 hours, I'd hope their estimate is much more conservative than Garmin's and has a lot less variance. Otherwise, I can't see the ACE LTE lasting until end of school day.