Battery charge lasts around 10-14 days depending on your settings.
At 20% battery level you should get a notification in the app to recharge your battery. The Tumbler has to be connected to the app at that time so the app can read the current battery level. If the battery gets low when the tumbler is not connected to the phone you won't get a low battery reminder. In this case, the battery will remain at the same level as the last time you connected the Tumbler to the app.
So please open the app a few times a day to make sure the Tumbler is connected and syncs data and you can also enable background sync for the Hidrate app so the Tumbler stays connected when the app is closed.
To charge, turn the Tumbler upside down and remove the puck to charge.
Place the puck on a flat surface and attach the magnetic end of the HidrateSpark charging cable to the puck. While charging every other LED on your puck will illuminate and fade in / out (every 10 sec.) green. Once fully charged every other LED on your puck will remain SOLID GREEN. It may take up to a few hours to charge the sensor puck. After charging and reassembling the Tumbler, the sensor has to be recalibrated within the app.
NOTE: Please avoid putting the charging cable near metal surfaces when it's not in use. If the cable comes close enough to a metal surface, it may connect to that surface with its magnets and cause damage to the cable
Please DO NOT try charging the sensor puck with any cables other than the one that came with the Tumbler as it may damage the sensor!