Why does my iPhone 3G Battery run on AC power?

okay. my iphone will be close to dead, or half instrument dead, or almost dead completely.

but when i plug surrounded by my charger, it automatically starts running on AC power. i'm like, what the heck?!? i know that because it shows the little Plug as the symbol, instead of the lightning bolt.

sometimes the lightning bolt will show, but other times it will run on AC power.

i just want to know, why or how i can fix this? its really irritating.

sometimes i will own my phone plugged in over night to charge, and next when i wake up and unplug it, it HASNT been charged at adjectives. battery will be at 20% and ALL night, it have been running on AC power. i dont understand.

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Answers:    that finances that your phone is able to charge.
its a manufacturer irregularity.
your wireless carrier/apple should replace it for you.