i just went thru a similar thing with the same laptop. wiped it and the problem stayed. my battery didnt say service was needed tho. the lateat update caused to to idle super warm and no processes were taking up a noticeable drain. very frustrating.

i do a lot of freelance work so i finally just bit the bullet and bought a new laptop.

the funny thing is, this laptop is still pretty good for Dev and photo work. anyways good luck, it feels like planned upgrades to me.