CPU not changing speed during idle state

[Tombstone_actual]

I recently bought this Acer Aspire 5 a515 51g laptop and it was preloaded with windows 10 home edition single language. The specs of my laptop is as follows:
CPU- i5 8th gen 8250U 1.60~1.80GHZ (boost to 3.4ghz)
GPU- NVidia GeForce Mx150
Display- 15.6inch 16:9 1366x768
HDD- 1tb wd 5400rpm
RAM- 8gb ddr4
SSD- none
OS(current)- Windows 10 home single language (version- 1709, build- 16299.309)
Earlier it used to give me 5-6 hours of average battery life when I’m running on battery saver mode, that said I also used to tune down unnecessary things such as cpu max power consumption level to 99% on battery, brightness to minimum, disabled background apps and turning on the battery saver. I noticed that even on battery saver with power limit to 75% the cpu would go up to 1.57-1.61ghz on peak requirements (although not necessarily cpu load being 100%, I’m talking about watching videos browsing copying stuffs etc.), it’d go up to 3.3ghz or so under stress and when idle it’d automatically tune itself down to around 0.80ghz or 0.50ghz thus saving power. Now after a recent update of windows, I found out that the average battery life has gone down by more than an hour or so, now it shows an average battery life of 4hr30mins to 5hr15mins after a full charge with the same settings. I also noticed that even in the idle state the cpu wouldn’t undervolt itself and it remains at its peak power state i.e. at 1.57-1.61ghz at 75% power. I suspect that there’s some hidden service or app that was added after the update that requests the cpu to run at its peak clock. The interesting thing is that the cpu load at idle is 0-1%. I couldn’t find any app which is consuming the cpu that is making it run at its peak clock. This is affecting my battery life. Has anyone any idea to what it might be and its possible fix? I’ve already tried bios- there’s no option to tweak the cpu over there. I’m currently running the cpu at 10%(0.40ghz) power state to conserve battery for my casual works which includes writing, browsing and watching videos, but it’s kind of sluggish at times when I open too many tabs or switch between apps or run any big sized video. Earlier I wouldn’t have to worry about it because the cpu would automatically ramp itself up to its needs and tune down during casual stuffs to conserve the battery. It’s not the same experience anymore. Any suggestion will be helpful. Thank you.

 

[photonboy]

What are you doing that would cause you to run out of power?

Are you going to work/school and using it for 4+ hours until it drains?

AFAIK the "Power Options" in Windows are the main power savings. I don't think an application can request the CPU to go above any limits there.

Also, have you TESTED to see how long it lasts? It's possible the reported life isn't completely accurate or maybe the update actually increased the accuracy of the estimate but it's now lower. Not sure.

I'll try to find more info.

"I also noticed that even in the idle state the cpu wouldn’t undervolt itself and it remains at its peak power state i.e. at 1.57-1.61ghz at 75% power."

*So what's the "Minimum Processor State" set to? I believe it should be 5%.

 

[photonboy]

For Battery Saver mode what percentage for batter life did you choose for when to kick in? 20%? 100%?

BTW, there's a BIOS update as of March 21st. Possibly related to Spectre/Meltdown:
https/www.acer.com/ac/en/CA/content/support-product/7244?b=1

There's also a "Turbo Boost Driver" in the software downloads which you should already have installed (or if not Windows Updates would likely install) but if completely stuck maybe run it on the off chance it fixes some glitch.

Other:
FASTSTARTUP if on will also reduce battery life... that's what your Manual says but I'm unclear if that works if the PC was turned off fully or via Hibernate... supposedly it will startup periodically to check for e-mail or whatever then shut down again if Faststartup is on.

Obviously if you use SLEEP (which usually produces a flashing LED somewhere) you're still using power.