Why am i having this wierd battery problems?

My android device: LG G3

I kept having this wierd problem where my phone always turns off when it reaches the battery percentage of 40 to 36?

Another problem is? That my battery always drains super fast.

Thats not all.. After it shuts down.. I charged it 3 mins later i tried checking it.. It already says 70 percent?.. When i opened it.. Or i tried powering it on.. What do i see? 89 percent?

I tried:
-Hard reset
-updating it through pc to get the latest update
-even buying new batteries?

That sounds like a dendrite. (See Lithium Battery Dendrite links if you're interested.) You need a new battery.