If you want to check the Battery status, just go to the "You" tab and "Stats".
The Battery Status displays how many words/sentences of the learned ones are forgotten (discharged), and need to be reviewed (charged again). 
If you want to check the Battery status, just go to the "You" tab and "Stats".
The Battery Status displays how many words/sentences of the learned ones are forgotten (discharged), and need to be reviewed (charged again).