15w vs 45w TDP CPUs and Battery life

Discussion in 'Hardware Components and Aftermarket Upgrades' started by Kyle, Apr 20, 2019.

  1. Kyle

    Kyle JVC SZ2000 Dual-Driver Headphones

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    I want to get a laptop which will maximize battery life. For normal web use and work, how much would battery compare with the low power U cpus, and the 45w TDP intel cpus found in workstations?
     
  2. VoodooBane

    VoodooBane Notebook Consultant

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    Well i know my alienware 17 r3 which had a gtx 980m with a i7-6820hk(I think it was 45watt to 65watt?).i got 4-1/2 hours of battery life... juat a note i thought i mention.

    Sent from my SAMSUNG-SM-G928A using Tapatalk
     
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  3. 4W4K3

    4W4K3 Notebook Evangelist

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    I'm on an i5-7300HQ which is 45W TDP and c-TDP of 35W. Windows is fairly good about managing the switch between AC and battery power when plugged and un-plugged. With some configuring (Throttlestop) you can get the idle power usage down to something like 0.7W even out of this 45W chip. My point being, the overall TDP rating is not indicative of a lower power usage or a longer battery life.

    Your best and most sure way to ensure longer battery life is to get a laptop which has a battery with a larger mAh rating. They vary greatly. You can configure the CPU to use as much or as little power as is available (0-45W essentially). That's my take on it.
     
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  4. bennyg

    bennyg Notebook Virtuoso

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    Undervolt as much as is stable as well.

    You can use Throttlestop to automatically switch profiles when on battery, limiting multipliers, setting speedshift ("EPP") to a higher setting. It'll take a bit of testing to see what settings are the most efficient balance of acceptable performance vs power saving, and that depends on your workload.

    You can't directly turn the 45W into a 15W by copying the multipliers as you can't go below base clock, but you can by setting the power limits low. Unfortunately Throttlestop only lets you tie current limit and speedshift to an auto ac/battery or hotkey switched profile, the rest are constant platform wide settings.

    For example I can constrain my 9900K all the way down to 35W (~2ghz under 100% load) only by using speedshift, nothing else will let it run below base clock.

    So confirm as best you can that the models you consider have these settings unlocked for you to change. Check the owners lounges here on NBR, if you can't find the info, just ask current owners :)
     
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  5. Che0063

    Che0063 Notebook Consultant

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    Although their idle power consumptions are similar, there are SIGNIFICANT disparities in power consumption between U and H chips. H series (45W mobile CPUs) far more aggressively shift their CPUs out of deep package C States. For example, simply moving the touchpad or mouse will force the package to move mostly to C0 on H-series CPUs, whereas my Y CPU will keep most of its package in C2/3. For doing simple tasks such as browsing, H CPUs spike to much higher wattages than their U series counterparts. You will get much higher performance on heavy workleads though.

    Speaking from experience, I've simply never got better battery life with H-CPUs. On my Mi Notebook Pro, (8250U w/60Whr) I get 10-12hrs, on my Teclast, (7Y30 w/37Whr) 10, and Aspire (7700HQ/ 60Whr) 6-8hrs max.

    The design of the motherboard and its components matter a lot. (PCH, RAM, SSD, dGPU). The 8250U/7700HQ/7Y30 all have the same idling wattages of 0.3-0.4W. Yet their minimum system power draws vary with the above systems: 3.7W/2.5W/4.8W respectively.

    For "normal web use and work," I'd go with a U CPU (i5/7 8XXXU) on a laptop with at least 50Whr of battery capacity.
     
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  6. tilleroftheearth

    tilleroftheearth Wisdom listens quietly...

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    If you want maximum battery life per charge, get a notebook that offers the biggest battery or batteries, period.

    A current i7-QC or higher CPU with at least 16GB of RAM need only apply. Doesn't matter if it is a big CPU or not. What matters is you get a CPU that can drop to idle as quickly as possible (because it finishes the workload it is presented) and a chassis/design that gives you more than a 30WHr battery at a shot.

    How much battery life do you actually need though (in hours)? What is your actual 'normal web use and work', workload? What is your budget, if any?

    Any notebook can be made to maximize the battery. But if you need a full 8/10 Hr run for more than watching youtube for half that time, the rest of the details matter too. ;)
     
  7. VoodooBane

    VoodooBane Notebook Consultant

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    I was just saying for my alienware 17 r3 just browsing and YouTube only via battery battery was 4-5 hours. Not other changes with throttle stop or anything. BasicallyI. Am just making the point if you have an optimus laptop with a good battery size you will get what you need if not more.

    Sent from my SAMSUNG-SM-G928A using Tapatalk
     
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  8. Kyle

    Kyle JVC SZ2000 Dual-Driver Headphones

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    Thanks for the pointers everyone.

    One thing which makes battery life somewhat problematic for me is that I use linux, so there aren't that good optimizers.

    I have the 17" Dell Precision 7730, and I only get about 3.5hrs on light use (in linux). Battery health is 95%.

    I looked at the 15" 7530, and it also has similar battery life.

    Strangely, the 15" 5530, with the same H/Xeon CPUs seems to get 8hrs of battery life, which is puzzling to me. How are they doubling the battery life?

    The one thing which I don't like is the emphasis on thinness in the 5530 - I want something semi-rugged, for use on the road.

    I want 8hrs of battery life in Windows (which means 7 hrs in linux which will reduce to 6hrs in a year due to battery degradation).

    One laptop I am looking at is the lenovo T580. It has two batteries, 4k screen, 32GB ram ....

    Budget is 2.3-2.5k with 5 year warranty, lower is better.

    The dell XPS and Asus zenbook ux533fd were also suggested in this thead: http://forum.notebookreview.com/threads/15-inch-laptop-with-battery-life.828438/
     
  9. Kyle

    Kyle JVC SZ2000 Dual-Driver Headphones

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    Do they make laptops with bigger batteries than 97whr?
     
  10. Che0063

    Che0063 Notebook Consultant

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    Careful laptop setting optimisation and hawk-like monitoring of background processes can give battery life a big boost :p. I bet you if I got a U CPU with 97Whrs of battery, I'd get 19.5hrs out of that.

    In terms of the 7350 and 5350, maybe a device was being kept on. Check idle (min brightness) battery discharge rates. 15" devices should get down to less than 5W.

    I'm assuming you're already knowledegable with Powertop and the other battery configuration thingy for linux?
     
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