[Android Central Question]

It's kind of like, when you're phone is at 20% and you charge it up for 10 - 12 hours and it only reaches 45%. I thought that it was kind of like a bug or something? And when I restart my phone, it decreases by 5%. What do I do?

[belodion]

Try first a different charging lead.

It is, incidentally, generally regarded as bad practice to routinely discharge phone batteries much below 40%.

[B. Diddy]

Welcome to Android Central! If different charging cables and plugs do the same thing, then it may be that your battery is starting to fail. Regular deep discharges (i.e., letting it drain to zero or close to zero) can significantly shorten a battery's lifespan.