Magician, empty backup battery!!HELP!!

[Guest vedtom]

Hy,

for a few days my phone id disconnecting tha calls I recive.Today morning when my phone was alertng me because the lw battery another icon was displayed on the top of the screan...a little circle or what.After that I went to battery settings and I saw that tha main battery is 80% but the Backup battery is 0% (empty), how to recharge that????HELP!