Why does my lg extravert 2 not turn on without charger?

[C00L FIRE]

Yes my phone is charged and i can even check it but the phone only works when its plugged in. Otherwise every time i take the charger out, it doesn't seem to work. I tried holding the power button for over 20 seconds and each time i held it for around that time, there would be the lg logo sign that will be there for a second and then turns black screen again. I even tried taking out the battery and putting in the charger and putting in the battery and still doesn't work. If anyone can figure out this problem, that would be really helpful. I don't have a sim card and i don't plan on resetting my phone though. Thanks

 

[Rukbat]

there would be the lg logo sign that will be there for a second and then turns black screen again.

That a sign of an almost dead battery. Have you charged it for at least 2 hours without trying to turn it on? If you have, the battery is dead and has to be replaced, but if you haven't, try that first. (Plugging in the charger when the battery is almost dead gives you enough charge for about half a second. Charging it for 5 minutes more gives you maybe a whole second. Turning it on in either case kills the battery again.)