15w vs 45w TDP CPUs and Battery life

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?

 

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.

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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.

 

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

 

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.

 

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.

 

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.

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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/

 

Do they make laptops with bigger batteries than 97whr?

 

Careful laptop setting optimisation and hawk-like monitoring of background processes can give battery life a big boost . 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?

 

Between Dell, Asus and a ThinkPad, do you really think there is any choice?

I would normally suggest looking at the updated T590, except they don't seem to be offering two batteries anymore.

The X1 Extreme is also a consideration and may prove to be the better option (the 4K screen is nice to have, on any system you're considering, but if you really value battery life...).

Take this for what it's worth; forget about a warranty past a year (which almost everyone gives by default). If the platform hasn't shown signs of weakness within that first year, then a warranty is just extra profit for them, directly out of your pocket.

I would recommend you buy the most hardware/horsepower you can (and depending on your workflow, forget about discrete video too), including the battery capacity. The budget you have is in the ballpark, but don't be afraid to drop the warranty and up the cost, if the final platform (overall) warrants it.

Instead of wasting $$$ on a warranty that you will most likely never use? Order the TP with two or three batteries together with it at time of purchase. Depending on how long you think you'll have that system for. Don't wait, or leave it for later... buy/order everything at once.

An Asus may be a consideration for me at half to two thirds the price of a TP. But at equal cost? It pales to what a ThinkPad offers, IMO.

My current thoughts on this (updated) info (Maxed out: best processor, max RAM, most battery):

Τ590 - Maxed out. Keep, use and enjoy for at least 3 years, upgrade then if/when needed.

T580 - Maxed out. This may be the best option for you. Drop the warranty and add a few batteries. With enough batteries kept fresh and in proper storage, with an assumed lower-end workload demand, this may last longer than all here, but what you'll be missing sorely on? Performance in a few short years. Not that this is a bad option, but when you're buying a two-year-old platform already, it may not be the wisest choice to spend considerably on batteries for it to keep it around even longer.

X1 Extreme/P1 (If you really need professional graphics) - Maxed out? A solid 3 to 6-year purchase. Depending what 'max' and 'workload' means to you.

Asus UX533FD - an 18 to 24-month purchase as a temporary stop-gap (if you need a system now), while saving up for a true platform upgrade in all aspects.

Yeah, just some of the things that rattle around my brain when a purchase is being considered with a 'budget' throwing a wrench into optimizing things as they need to be.

 

I was not, but after reading your post, I installed TLP and powertop
TLP managed to increase the battery life to about 4hrs (from about 3hr20 minutes).
I have not done undervolting yet.

Hey, Dell makes good business laptops (their precision line in particular)

It's worse. T590 does not offer 4k screen (580 does), and the max memory I can configure is 24GB (in 580 it is 32GB)

X1 extreme looks nice, but the battery life in linux (~6hrs) is a tad low.

That's an interesting strategy...

 

I beg to differ. If that were the case for everything, then no one would buy fire, vehicle and other insurance for physical objects. The thing with Dell's warranty is that they completely replace out components altogether for however long the warranty period is—so just like the Ship of Theseus, you could have a fundamentally good-as-new notebook even after 5 years of ownership. Not a bad deal for hardly $300 more.

Plus, buying batteries only to keep them in storage is a very bad idea for longevity. It's better to get an in-use battery replacement over the several years that the notebook is intended to be used.

To address @Kyle's question about battery life on the 7730/7530 versus the 5530:

The reason is simple: even on Optimus, the Nvidia GPU is left on. There is no other explanation for it, and no other fix besides waiting for Dell to push out a firmware upgrade of sorts. I've gotten tired of nagging Dell, and what with my finals approaching, I really haven't got much time to spend on long telephone calls. Perhaps over the summer break.

Overall, however, I do agree with @tilleroftheearth's assessment of the thing: if you are prioritising battery life, you should definitely get a U-series CPU, as large a battery as it can hold, and other components that minimise battery consumption as much as possible.

 

You're welcome to differ, but your argument is not sound.

We're not talking about everything here, I was talking mostly about the ThinkPads. They are a known element.

As for the Dell warranty? Yeah, I have seen what you state first hand (on a client's, not my own systems), but they were as worthless with 98% of their internal parts replaced as when they were brand new. Not a reason to have a warranty. That is a reason to buy a better platform, period.

If you think that a battery you buy today and store properly will be worse off than what a manufacturer will sell you a few years down the road, then you're storing them wrong.

That $300 more is huge on a $2.5K system. The RAM could be maxed out, the CPU could be maxed out, maybe both (or a good balance), giving a superior performance every single time it is used, for the full lifecycle of the platform.

To state the above another way. That $300+ could take a good machine and make it a great one, on the right platform. If you can increase the productivity from day one by 30% (and to over 100% or more by maxing out the battery life, as in this case) or more by maximizing the CPU+RAM combo, you are effectively buying a platform that will be just as competitive two or three years down the road, while enjoying its advantages each and every day you use it.

The safety net of a warranty has long since lost its luster to me. These platforms are not something we're buying off the back of someone's truck. They are a known commodity and getting more, for less, is the only better option to choose. As long as you buy a platform that is actually built to last, of course.

 

I'll head over to the Dell forum to inquire about 7730/7530 battery life on configs which do not have a seperate graphics card

@tilleroftheearth you make some good points, but for me $300 for a 2.5 system is just 12% overhead, and it gives me some peace of mind regarding accident damage protection. You are right I've never had to use warranty after the first year: but I'm the worrying type, so the extra 12% does go towards increasing productivity by calming my poor brain down.

 

That's cool.

But I doubt you worry less after spending it though?

Accident protection? Okay, I can see that being useful for some. Hope you choose the best system for you.

 

Sshhhh. Let me be in denial

 

I'd be seriously worried if Dell was disabling integrated graphics. Does the BIOS prevent Optimus from turning the GPU completely off?

In my experience, as long as the dGPU is enabled, Optimus will turn the GPU basically off. When you disable the dGPU, you also disable Optimus. on MX150/GF920/GF945M cards was the case for me. Without optimus, they drain an extra few watts.

 

The BIOS has a straightforward radio button to enable/disable graphics switching, or Optimus.

My point was from an observation of power draw, which did not improve (i.e. decrease) when Optimus was switched on. I have a 97 Whr battery (that has since experienced 14% of wear, mainly due to accumulating so many charge cycles because of the poor efficiency of the Precision 7530), and I see 5 hours of battery life, regardless of whether or not Optimus was enabled. From this, I deduce that even though HWInfo, GPU-Z and so many other utilities report that the GPU is powered down, I believe there still is some phantom ~6-7 W of power draw somewhere, and it must be the dGPU.

Edit: the Precision actually has the DGFF Quadros, and I tried unplugging the power cable to the daughterboard. The system refused to boot altogether.

 

With the Thinkpad P72 whose specs are in my signature, I get a minimum of 6h battery life with:

- 0.125mv undervolt
- the dGPU turned off entirely. This is crucial
- TLP 1.2.1
- a minimal desktop environment: Xorg + i3wm
- a recent kernel (5.0.8)

The biggest gain comes from turning off the dGPU entirely with bbswitch. It reduces wattage by 6-10W. And idle temps as well (about -10 degrees), providing better performance.

There's a great guide here to get the best of the battery on Linux:

https://old.reddit.com/r/thinkpad/comments/alol03/tips_on_decreasing_power_consumption_under_linux/

It's largely possible to have battery life as good or better than Windows, but it requires a bit more effort.

.

 

The thing is, this simply does not happen on the Precision 7530/7730.

On the 97 Whr battery, with an average 8 W reduction in power consumption, that means that I'd see 15 W – 8 W = 7 W. And on a 97 Whr battery, that translates to nearly 14 hours of battery life.

Obviously, I don't see such improvements. I have even tried to disable the functionality to run the video out ports through the dGPU and go iGPU-only. Nothing at all. There is 7 W of power going nowhere at all, and I am determined to get to the bottom of this.

Linux has not been helpful at all, as much as I have observed.

I haven't really begun to pester Dell about this, but I think I will.

 

I can confirm that on my P72 with the Quadro entirely turned off with bbswitch, the reduction in wattage is dramatic:
currently with mostly Firefox running, a few terminals and Eclipse running (but idle), wifi off, thunderbolt enabled, 4K panel at moderate brightness, I'm looking at 2-6W.
If I load the nvidia modules (which will turn the Quadro on), I'm looking at 12-16W.

You should be able to turn off your dGPU with bbswitch, but it can be tricky because you need both the nouveau (open source) and nvidia (if using the proprietary drivers) modules not loaded. nouveau modules are better blacklisted anyway.
With the proper tweaks, Linux battery life can be outstanding. And single-core and I/O performance is better than Windows, but that's another topic.

Not sure about what Windows 10 is doing when the dGPU is not used at all but I doubt it turn it off entirely like it is possible on Linux.
Other solution is to disable the dGPU in BIOS (if possible) but this is not super practical if you occasionally need it. In my case, I only need it for connecting to external monitors as the video ports are wired to the dGPU and this cannot be changed.

 

I thoroughly agree with your points about Linux generally being superior to Windows w.r.t. battery life, I/O and single/multi-core performance. I do plan to seriously experiment with Linux after 7 May or so. The Precision actually has BIOS options to change the video output ports to be routed either through the dGPU or the iGPU, and they don't help, either...

 

An personal question:
A laptop with 45w TPD and battery of 62 Wh.
A laptop with 15w TPD and battery of 36 Wh
Could you tell me which battery lasts more hours? If your main interest is the battery life, what would you choose?
Thanks

 

The 62 Wh config.

 

Thanks tilleroftheearth

 

Thinkpad T580:

Processor : 8th Generation Intel® Core™ i7-8650U Processor
Display : 15.6" UHD (3480 x 2160) IPS anti-glare
Memory : 32 GB (16 + 16) DDR4 2400MHz
Graphic Card : NVIDIA GeForce MX150 2GB GDDR5
Keyboard : Backlit Keyboard
First Hard Drive : 500 GB Hard Disk Drive, 7200rpm, SATA3, 2.5", OPAL2.0 - Capable
System Expansion Slots : Smart Card Reader
Front Battery : 4 cell Li-Ion 32Wh
Rear Battery : 6 cell Li-Ion 72Wh Cylindrical
Windows 10 Pro

3Y Onsite upgrade from 1Y Depot/CCI
3Y International Services Entitlement
3Y Accidental Damage Protection
3Y Sealed Battery

Final Price including tax: $1417
EDIT: $1295 with 16GB ram (one slot free)

MUST RESIST buying...so difficult....

 

Omg yes.

That battery configuration, is just... wish so many other manufacturers did it. Just because processors get more efficient over time, doesn't mean you should skimp on battery capacity.

I like dual-battery configurations very much.

 

These days a simple removeable battery seems too much to ask. For the price of an extra battery: double run time, instantly, stuff all engineering required, less than 1 minute of downtime these days with fast SSDs.

The first laptop I had at school had a removable main battery, and a hot swappable ODD bay secondary battery. Didn't even have to hibernate to add or remove a battery.
That was 1997.

My partner's also saved her laptop motherboard twice after spilling on them by powering off and instantly removing the battery.