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6 Posts

12-21-2019

Netherlands

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C940 15 4K Battery & Geforce Experience

2019-12-21, 9:28 AM

Hi there.

 

Yesterday i received my Lenova C940 15.6 UDH Laptop and I got 2 problems.

Love to gain some intel from the community, lenova to improve battery, fix the geforce exp issue. 

 

First problem is my battery life, I tested it out with youtube open and some normal windows apps, and got around 2 Hours of Battery life.

(On 35 brightness)

I mainly bought the laptop for work, Adobe (indesign/illu/photoshop) to hopefully last at least 4-5 hours on battery, but i doubt i get even 2 out of it now.

 

The Second problem is Geforce experience, it doesn't let me download drivers, Windows is not compatible it says. 

 

I have done all driver updates from Lenova, and Windows updates. 

One drive is off, Location is off, Battery is on the second button,

Brightness is on 35. 

 

Hope to receive some help from the community!

 

Any way to improve battery is welcome!

 

 

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144 Posts

12-08-2019

United States of America

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Re: C940 15 4K Battery & Geforce Experience

2019-12-21, 17:11 PM

From someone who has searched endlessly to improve this really bad battery the c940's are shipping out, these are my findings as of now (from least to more "drastic" measures:

0. Check if you have any apps/services that are draining your battery quicker than normal in Task Manager

0.5 Make sure you have everything updated (Windows 1909, BIOS updated) since Windows 1909 apparently optimized battery life on c940's (can confirm and others report the same here). You can download it directly from Microsoft's site: https://www.microsoft.com/en-us/software-download/windows10 ) and check BIOS updates inside Lenovo Vantage. You can check which version of OS you're on by pressing the Windows key + R (run) and typing "winver".

1. Make sure your battery slider is set to Better Battery mode (click the battery icon and your slider will appear, shift it to maximum left)

2. Make sure you're using Power Saver mode in Lenovo Vantage (there are 3 modes, Power Saver, Intelligent Cooling, and Performance. You can see this in Device settings in Vantage or by pressing Fn + Q until you see the battery icon appear on your screen)

3. Create a power plan (if the option appears for you) and limit max CPU processing percent. I can't really confirm how much this saves battery, but if you limit your CPU's performance by say up to 70%, it'll peak there and not use 100% of the CPU's capabilities so it should drain battery less (it may become a tad slow on heavy tasks, but you can customize it to however you wish).

To a more heavy extent: (USE WITH CAUTION)

4. Undervolt your CPU. This can be done with Throttlestop, and what it does is basically decrease the voltage your CPU receives since basically every laptop provider sends their CPUs overvolted to avoid the hassle of calibrating each one to best stable volts.
From my personal experience overall: undervolting has for sure given me extra battery life on my 14 inch C940 UHD (not sure by how much but I'm getting now average of 6-7 hours and sometimes 8 when idle). Originally I set my undervolt to -80 mv, however this caused my c940 to not want to wake from sleep if I do some extreme tasks (like gaming). This was fixed by downloading 1909 again from the Windows site (keeping my files and everything) and proceed to adjust the undervolt to -60 mv. At these volts I have found it pretty stable, even while gaming. Since you have a c940 15 inch UHD, probably the mv you're more stable at will differ from mine. That not wake from sleep issue appears to have only happened to me, but it's happened on 2 c940's UHD 14 inch I have owned, so I assume there are other people with that issue who haven't reported it yet. If you make sure not to undervolt too much you should be good. Tutorial here: https://www.maketecheasier.com/reduce-cpu-temperature-undervolting/

 

Note: in case you still find battery life poor, C940's come with fast charging (charges 80% in under an hour), but it is limited to only working when the lid is closed/when the PC is turned off. This might be due to the 4K screen taking up a lot of juice when on, but I suspect this is a software limitation that Lenovo can fix hopefully in a future, since FHD users have reported same slow charge rate when opened  (my c940 UHD 14 inch takes about 3 hours to max charge by it's USB-C 65 watt charger it came with that charges at only 15 mW rate). 

 

Hope this helps! (and don't know on the Geforce thing lol)

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11 Posts

08-26-2016

Austria

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Re: C940 15 4K Battery & Geforce Experience

2019-12-31, 0:39 AM
About your GeForce Experiece / driver issues... welcome to the club - https://forums.lenovo.com/t5/Lenovo-Yoga-Series-Notebooks/C940-15-Nvidia-Update-through-Geforce-Experience-not-working/m-p/4603267
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40 Posts

05-10-2014

United States

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Re:C940 15 4K Battery & Geforce Experience

2020-02-22, 6:48 AM

Hi,

 

I recently purchased the C940 15" with the i9-9880H processor. I was a little skeptical about this purchase because of how many people are struggling with battery life. I'm rarely away from my desk and a power supply, so I was more going for this on account of the NVIDIA graphics card + the i9 processor.

 

I can verify that all of the suggestions by @liopag2 are extremely useful and do help battery life. My observations have led me to believe that if you can keep the fan from ever turning on while on battey, your battery life will be great. As soon as it turns on even at a low speed, the estimated battery life tanks. Undervolting should reduce the power required to maintain a specifc CPU clock speed, if I understand correctly. I am currently undervolting my i9-9980H at -125 mV CPU core, -125 mV CPU cache, and -60.5 mV iGPU. My system is perfectly stable even during heavy stress tests.

 

One of the other concerns I had about this laptop prior to purchase was whether it would be able to sufficiently cool itself to get the maximum benefit out of the powerful i9 processor. The obvious answer is most definitely not. When I run any program that uses 100% of all available CPUs, my CPU is thermally throttled to ~2.8 GHz to keep the TDP at 45W (and CPU temperatures at 70 C), which is barely above the 2.3 GHz of the base clock speed for the i9-9980H.  However, when I undervolt at the settings described above, my CPU is still thermally throttled but instead hangs at ~3.2 GHz on all cores while the TDP is still at 45W and the temp is still 70C. I don't think I can undervolt much more without risking system stability. I'm not sure whether these settings are translatable to the i9-9750H either.

 

I'm still wondering whether the 6 core i9-9750H would perform better in this situation by due to the higher base clock (2.6 GHz).  Specifically, what performs better -- the 12-thread that can turbo boost all cores to a clock speed higher than the 3.2 GHz, or the 16-thread chip stuck at 3.2 GHz. This is something I wish Lenovo would have made clear, that you won't actually hit what your processor is capable of because the cooling capabilities of the C940 are insufficient.

 

 

Edit:

You can also use ThrottleStop to set the Speed Shift - EPP much lower than you can using Windows settings. For example, Windows sets this parameter at "178" when you click on the battery icon and slide it to "Better Battery" mode. I think that "Better Performance" is set to 87. You can go as low as 255, which will drop your idle core speed even lower. If you set it to 0, your cores wlil idle at peak frequency, which for my CPU is 4.8 GHz. Setting to 255 will make your laptop seem a litlte slow, but if you have enough cores you really won't notice too much. This has been one of the better ways I've found from keeping those dreaded fans from turning on.

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144 Posts

12-08-2019

United States of America

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Re:C940 15 4K Battery & Geforce Experience

2020-02-22, 15:54 PM

Nice find on the Speed Shift thing, did not know about that feature until now!

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1 Posts

12-13-2019

United States of America

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  • Message 6 of 9

Re:C940 15 4K Battery & Geforce Experience

2020-03-03, 19:28 PM
Fantastic thread ! Also for the more brave re pasting does wonders with your Temps and battery life.
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40 Posts

05-10-2014

United States

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Re:C940 15 4K Battery & Geforce Experience

2020-06-15, 21:53 PM
Hi @Nik36, what thermal compound did you use for repasting that worked so well?
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40 Posts

05-10-2014

United States

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  • Message 8 of 9

Re:C940 15 4K Battery & Geforce Experience

2020-06-15, 23:28 PM

Also, this video is a phenomenal resource demonstrating how to do many of the things listed in this post using the 15" Yoga C940. I definitely recommend it. It helped me figure out how to use MSI Afterburner so my GPU runs much cooler and more stably.
 

 

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41 Posts

02-21-2020

Switzerland

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  • Message 9 of 9

Re:C940 15 4K Battery & Geforce Experience

2020-06-16, 8:25 AM
It is frequently recommended to update BIOS when trying to resolve issues with the C940 series. Here too. However, please note that only the C940 14" has received a BIOS update to this date. (16. Jube 2020) The C940 15" has not received any BIOS updates so far. A BIOS update was indicated by Vantage earlier this year but in fact only the date of the old version was changed in the file description (to April 2020). Nothing was changed in the downloadable files, including the docs and readme files. Why they would do duch a thing is quite beyond me. I can only assume that the employee charged with updating the database failed to upload the new files by mistake abd nobody ever noticed. p. s.I did refer to this in the forum when Vantage advised ne to update BIOS.
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