XPS 15 9500 and U4320Q monitor - USB C Power Delivery

I just got an XPS 15 9500 (i7-10875H, GTX 1650 Ti) and a U2421E monitor and was similarly concerned about the charging functionality. My laptop came with a 130W power adapter and the monitor is rated for 90W power output via usb-c, but so far so good. I tested the charging rate of the monitor vs the laptop power adapter and they were the same in a certain context. My battery happened to be at 43%, I had minimal apps open, and I plugged in the power adapter and hovered over the battery icon; it read "1hr 16min to full charge". I unplugged the power adapter and connected the laptop to the monitor (usb-c) and after a minute it also said " 1hr 16min to full charge", despite a consistent yellow warning symbol on the battery icon that said "slow charger". So perhaps under light use the monitor will be sufficient to charge the laptop at the same rate as the power adapter can.

When connected via usb-c to the monitor, if you click on the battery icon it will show you a "power mode" slider, with one end being best performance, and the other being best battery life. I had it on "best performance" and didn't notice a difference under light use. that may all change with heavy use (photo/video editing, rendering, gaming, etc.) btw the video, ethernet and any usb peripheral worked great over usb-c. i tried daisy chaining the u2421e to a P2417H monitor but it didn't work, not sure if the p24 supports daisy chaining though.

@fatslice  90W may be fine for workloads that don't involve the NVIDIA GPU, in fact the XPS 15 9500 configurations that don't include an NVIDIA GPU come with 90W power supplies.  But if you start using that GPU, especially if you're also trying to charge the battery at the same time, you might run into the limitations of that 30% power shortfall.  In terms of daisy chaining, I would expect the P2417H to work just fine at the end of a daisy chain since the display at the end of the daisy chain doesn't have to support daisy chaining at all.  It only needs to support DisplayPort 1.1a, and even DisplayPort 1.2 was well established long before 2017, which is the "model year" of the P2417H.  Did you enable MST on the U2421E?  And are you using a regular DisplayPort cable to connect the two displays rather than something like DisplayPort to HDMI?

@Jenu24  Glad you've found my explanation useful.  In terms of further explanation, using a display that provides 90W to the attached system to drive a laptop designed for 130W won't damage anything.  But your battery might not charge as quickly as it otherwise would, and/or it might perform more slowly than it would if you had a 130W power source connected.  The latter is more likely if you're performing tasks that rely on the GPU, such as playing games, rendering video, mining cryptocurrency, or running any other applications that leverage the GPU's computational abilities.  But at the end of the day, the XPS 15 with NVIDIA GPU was designed for a 130W power budget, and you're planning to use it with a power source that only provides 70% of that power budget.  As in the financial world, if you have a budget that plans to spend/consume more resources than are actually available to be spent/consumed, then cuts may need to be made in order to operate within the confines of that reduced level of resources.  Whether those cuts in terms of battery charging speed and performance are acceptable to you in exchange for the convenience of a single cable solution without having to spend more on a full docking station (which would allow 130W power delivery and single cable connectivity) is up to you.

@jphughan 
Thanks for lightning fast response

Ok, when its safe i feel comfortable now to run some tests and benchmarks. I will test 90W vs 130W in real aplications and benchmarks. I work a lot with graphic design and animations. I use nvidia cuda acceleration in adobe engines for example.

I noticed the XPS 15 gets quite hot during rendering in media encoder (72 celsius on GPU). Maybe i am fine having less performance, until i dont see real lagging or significant drop in performance.

Dock is also a solution, but they are quite expensive, and i already bought an Ultrasharp monitor with USB-C Hub Monitor in the name

@Jenu24  Well temperatures are another consideration. The XPS 15 for multiple generations has been unable to sustain peak performance over a sustained period of time because its slim and light ultrabook-style chassis can’t fit a cooling system capable of cooling the mid-grade components packed into it. I guess it’s possible that this has improved with newer models, but I would be surprised. I had an XPS 15 9530 (launched in 2013) and I logged both temperature and running clock speed of the CPU and GPU, and it was clear as day what happened.  As soon as one of those components hit a certain temp, its maximum clock dropped pretty drastically until temps dropped to a certain lower temp, and that cycle would repeat. So if you do a lot of graphic design and CUDA work, that might become an annoyance, although at that point your only option would be to buy something with a heavier, chunkier chassis that can fit a more robust cooling solution, like an Alienware system or a Precision 7000 Series system.  But those have even higher power budgets.

@jphughan  Ok, thanks. So thats why i see 90W as a compromise for regular use. And when i render a video for example it will take 3 minutes instead of 2 minutes (on full 130W) iam fine with it. Considering that the machine will not overheat and throttle performacne anyway. But these all are just my speculations, when my Ultrasharp arives i will test it.

My knowledge in electric topics is very basic. Please can you enlighten me in this simple question?

XPS power variants:

charge 130W = 20V * 6.5A

charger 90W = 20V * 4.5A

batery ?W = 11.4V * ?A

I ask because, isee a little noticable difference in performance when the XPS is pluged in charger VS on battery.

@Jenu24  Unfortunately I can’t speak to that spec of the battery, but it is fairly common for laptop performance to be slightly lower on battery than AC power. Less common and not used on the XPS 15 (though used on the XPS 17) is a design whereby the battery is used as an auxiliary power source even while the laptop is connected to AC, meaning your battery can drain while connected to power under sustained heavy loads, or throttle if the battery is too low to allow this. Dell calls this “Dell Hybrid Power”. I call it shipping a system with an undersized power adapter.

@jphughan  Hello, my new UltraSharp U3223QE has arrived. My first quick tests: original 130W charger vs 90W power delivery from monitor.

CinebenchR20

130W: 5221 pts

90W: 5124 pts

3DMARK timespy:

90W: 5044 / graphics 4584 / CPU 11694

130W: 5043 / graphics 4581 / CPU 11804

I will try to use this XPS 15 (9520) only connected to the monitor with power delivery. I turned off warning messages in bios and windows 11.

Yes, it worked for me. Glad to find it here. I already book for a massage because of this ongoing issue LOL 

@Jenu24​ still good?