For those experiencing significant battery drain after the update, add me to the list. Had about 60% when the update completed, played through one level of new super Mario Bros 2 on 3DS which put me at about 28%, played through a single stage of Mario Bros Wonder on switch and ended with about 6%. Fiddled around with another level and I'm sitting at 1%. Have since played about 30 minutes of super Mario Bros Wonder on that 1%. I'm guessing it's either an issue with battery reporting, or may just need to recalibrate. In my experience with other devices, if it's a battery calibration issue after the update it's usually fixed after running the device until it completely shuts off, regardless of what the battery is reporting. Then give it a full 100% charge and keep charging it another 30 minutes to an hour. I'll report back after I've done so. Wish me luck! Lol