I use this
app to keep track of my battery. It puts the percentage in the notifications area.
It does sound like you got a lemon. Hopefully the next one will work fine. Amazon is great about replacing problem Kindles. My first Fire after a firmware update wouldn't go past the start logo. I called Kindle support and the next day I had a new one in my hands.
I am much more careful now what I put on my KF. I've had no problems with it. It's not so much a Kindle thing but Android devices specially tablets are finicky.
I once bought a Coby tablet and it was defective from the time I turned it on. The battery gauge went up and down like a yo-yo.
I sent it back to Amazon and got my Kindle Fire instead.