100% CPU load, battery drain with no app minimized/running in the background I have a Xiaomi Redmi Note 4 S625 global variant (4/64GB).

Like a day or so ago, I noticed a quick battery drain (from 100 to 24% after a whole night idle and 2 - 3 hours of heavy use the next day) and from there it was dropping a percent every 2nd-3rd minute. It never happened before as its a 4000mAh battery and usually lasts around 2 days on normal use. I'm new to the smartphone world and I was reading online about the usual causes of battery drain including background apps consuming it and overcharging issue damaging the battery. I got worried as last night it was indeed left plugged in for like 2 - 3 hours maybe after a full charge. So either the battery is damaged due to overcharging, or its some software issue. Now what I noticed is the CPU usage is maxed with no app running in the background. I don't know if CPU-Z's usage info is accurate, but it's 100% when battery is like 15 or lower and 40-50% when battery is 20 or above. Maybe there's some background process or maybe its normal, I don't know. I'm pretty clueless at this point.

Here's a screenshot of CPU-Z: http://i.imgur.com/ZL2ipZm.png

Really appreciate if anyone helped me on this one. Thanks.
The reason of battery drain is mostly app. Either because of poor developing skills of developer or because app is doing something it shouldn't. Well if you overcharged it for 2 hours after full charge you don't have to worry no battery is that bad to die like that I mostly left phone on charger over night and I don't have any problems, yet :).
This picture from CPU-Z is it taken just when it loaded or few seconds later, because in every phone when it just loads it show high cpu usage..?
However you should see if there is any shady app like fancy keyboards or fancy galleries try deleting them and see what is happening or apps installed out of play store.
You can use app called wakelock detector to see what is causing problem. Download ; here you can find some help about it