My IOS 8 iPhone 6 Plus is not turning on!

I posted a question on here I think about a iPhone 6 Gold on iOS 8 that will not turn on.

it has been sometime since then and now a iPhone 6 Plus Gold I bought on iOS 8 will not turn on, so it says low battery, then the Apple logo for a few minutes, then it turneds off.

i believe it might need a new battery. If there is any thing else I should do please tell me.

thanks!