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November 9th, 2019 15:00

Understanding Dell laptops and USB-C power sources

(UPDATE: Since writing the post below, it seems Dell may be changing its 65W max power draw limit from non-Dell USB-C power sources.  I've seen reports from owners of the XPS 15 9500 (released in 2020) indicating that it will draw at least 90W from non-Dell sources.  But what I wrote below would still be true for most of the Dell laptops in use as of this update in July 2020.  Original post below.)

I decided to write this post because there seems to be a fair amount of confusion around Dell laptops and USB-C power sources, particularly third-party USB-C power sources, including how to determine what wattage the system is drawing from them and why power sources are identified a certain way.  Hopefully this will help Dell laptop users understand how to learn more about how their setup is working and why it's working a certain way.

First off, most if not all recent Dell systems will display an AC adapter wattage readout in their BIOS Setup interface under the Battery Information section, specifically below the battery graphic.  You can access your BIOS Setup by pressing F2 during initial startup.  When using non-USB-C power sources, i.e. Dell-specific AC adapters that use a barrel-style connector, the wattage shown there will be the detected wattage of the AC adapter, even if it's more wattage than the system will actually use.  So for example if I plug a Dell 130W AC adapter into an XPS 13 9350 that's only designed for 45W, it will still identify the power source as 130W, even though it will never actually USE that much wattage.  Using a Dell adapter that can provide more wattage than the system needs will not damage the system in any way.  I've kept a Dell 130W AC adapter in my living room for years and have used it with Dell systems designed for anywhere from 45-130W and it's been fine.

With USB-C power sources, the wattage readout you see there is a bit more complicated.  The reported wattage will be the maximum wattage that particular system will actually draw from that particular power source.  That might sound simple enough, but it isn't quite so simple, partly because of a restriction around USB-C charging that I've found implemented on multiple Dell systems.  Basically, as of this writing, multiple Dell laptops I've tested will not draw more than 65W from a non-Dell USB-C power source, even if the power source can provide more wattage and the system is designed for more wattage and would therefore benefit from drawing it.  In addition, the USB-C cable you use can matter.  USB-C cables that support USB Power Delivery are available in two versions: up to 60W (sometimes written as 3A, or amps) and up to 100W (sometimes written as 5A).  The latter are typically thicker in order to carry the extra power safely.  The relationship between watts and amps here is based on the current 20V max of the USB PD spec.  Citing amps is technically more precise because the higher amperage requirement is what drives the need for thicker wiring, but most customers think in terms of wattage.  Anyhow, if you use an "up to 60W" cable, you will never get more than 60W, even if you have a USB-C power source that can provide more wattage and a system that would otherwise draw more.

So let's look at some examples.  All of these assume USB-C power sources (as opposed to the barrel-style Dell AC adapters) and that you're using an appropriate cable for the wattage involved.  They also assume that you're using a USB-C source that can supply 20 volts.  Some lower wattage sources only supply power up to 15V, and although some laptops will work with such sources, others will not.  I didn't test such chargers.

Case #1: An XPS 9350, which is designed for 45W.  If you connect a 30W power source, the system will show 30W since that's all that's being offered.  If you connect a 60W power source, it will show 45W because that's the most the system is designed to draw.

Case #2: A Latitude 7480, which is designed for 65W but will take advantage of 90W when available.  If you connect a 30W source, it will show 30W.  If you connect it to a 65W source, it will show 65W.  If you connect it to a Dell dock that can provide up to 90W, it will show 90W.  But if you connect it to a non-Dell 90W power source, it will show 65W, even though other non-Dell systems will correctly show that power source as 90W.

Case #3: An XPS 15 9570, which is designed for 130W.  That's actually more than the official 100W max of the USB Power Delivery spec, but Dell has done something proprietary on this and some other 130W systems and certain docks (like the WD19TB) to stretch that spec to allow carrying 130W over USB-C.  They also make a 130W USB-C power adapter.  If you connect this system to one of those devices, it will show 130W.  But if you connect it to a non-Dell 90W power source, it will still only show 65W.  This is frustrating because this particular system would actually perform better if it drew 90W rather than 65W and is still refusing to do so.  In addition, I believe (but have not confirmed independently) that the XPS 15 models will not work at all with any USB-C sources that supply less than 60W -- although even a 60W source would be inadvisable overall.  Battery charging will be slow to non-existent and CPU and GPU performance throttling would be significant as the system attempted to operate within the constraints of a power supply that offered less than half the wattage it the system was designed to use.  A 60W source would be fine to use purely for battery charging while the system was asleep or off, but would not be a great choice while actually using the system.

Hopefully this helps people understand how Dell systems identify and work with USB-C power sources!

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August 17th, 2023 21:29

Additional video that might help:

4 Operator

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April 23rd, 2020 15:00

@Broccoli Cobalt  Glad you found my post useful!

If your laptops are designed for a 65W power source, then you shouldn't be considering USB-C displays that only provide 45W unless you also plan to keep the laptop's AC adapter directly attached as well.  Otherwise, while you won't DAMAGE anything by giving your laptop an undersized power source, you will create a subpar experience for your users.  First, the laptop will display a warning about an undersized power source every time it boots while connected to one, which will be an annoyance.  But worse, if a laptop designed for a 65W power source is only fed 45W, the laptop will try to operate within that reduced power budget by doing things like reducing its battery charging speed and reducing its CPU and GPU performance.

There are several USB-C displays on the market now that provide 65W or even 90W (although as mentioned above, as of this writing you won't get more than 65W over USB-C to a Dell system unless it's from a Dell source).  I would recommend that you consider one of those options.  Also keep in mind the note above about the USB-C cable coming into play if you want to go above 60W.  If the displays you buy supply more than 60W and come with a USB-C cable, then it's a safe bet that the included cable will be rated for up to 100W.  But if you'll be buying USB-C cables separately, you'd want a USB-C cable that supported DisplayPort Alt Mode for video and USB PD up to 100W, like this one.

April 23rd, 2020 15:00

I'm considering purchasing a large quantity of non-Dell USB-C monitors for my organization; however, the power delivery is only 45W while our standard issue Latitude 7390 2-in-1 laptops draw 65W. Your article is super helpful but it's still unclear to me if the 45W over USB-C will charge our laptops or if the monitors are incompatible or, worse, potentially damaging to the laptops. Would you clarify?

4 Operator

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April 23rd, 2020 15:00

@Broccoli Cobalt  CORRECTION!  I initially linked to the wrong type of example cable in my post above.  I've edited that post to link to the correct product.

June 29th, 2020 05:00

Hi, thanks for your insight. I've bought a Dell Latitude 3400, but I don't really want the expense of a few hundred £'s on a Dell dock too. I want to try a few cheaper alternatives (https://www.amazon.co.uk/gp/product/B07F2561H1https://www.amazon.co.uk/gp/product/B07MKC5Z1D/) but I need a USB-C charger, can I get anything that will supply 65, 70, 90 watts? Something like this? https://www.amazon.co.uk/Adapter-Charger-Ponkor-MacBook-Laptops/dp/B07Q9LRHH9/

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June 29th, 2020 06:00

@Smeg Head  This thread is purely about how Dell laptops handle USB-C power sources, so I'm not sure why you're posting about docking stations and "mini-dock" products here.  If you want a "mini-dock" product recommendation for your needs, then I would suggest that you create a new thread of your own that describes what system model you have and what device(s) you want to be able to attach through this device.  You'll get more visibility for your question and you'll avoid taking other people's existing threads off-topic.

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June 29th, 2020 07:00

@Smeg Head  Actually I just re-read your post and realized the only part you were asking about was the power source.  In that case, it seems the Latitude 3400 is designed for a 65W power source.  But if you'll be connecting it through a mini-dock, make sure that it supports providing at least that much to the attached system.  Some only pass through at most 60W because you need different cabling to exceed 60W, and some mini-docks might not incorporate that for their connection to the system.  Also be aware that mini-docks tend to "skim" some power from the attached power source when one is available in order to run their internal electronics and provide power to USB peripherals that are attached to them.  When the mini-dock does NOT have a power source attached, it would draw from the system, but the dock can't provide power to the attached system and draw from it at the same time.  The end result is that plugging a 65W power source into a mini-dock does not necessarily mean that the system will see a 65W power source.  It might see a 45-55W source instead.  So if you want to minimize the chances of warnings about a "Slow USB charger", you might want to look at a 90W power source to make sure you have enough capacity to pass through 65W even after whatever the mini-dock skims from that source.

And then you'll need a USB-C cable rated for up to 100W Power Delivery because most USB-C cables are only rated for up to 60W, and if you use a 60W cable, then that's all you'll ever get even if the power source could otherwise provide more and the device you're trying to power would accept more.

June 29th, 2020 16:00

Well, I tell you what...I bought my system...and I bought an additional power cord/charger/etc. Neither worked well from day one. I kept getting messages that said I was using a charger that didn't have enough power and that my laptop would drain battery power faster than it could charge! I was using Dell chargers! The one that came with it and the same exact one they sold me. I've replaced both...twice!!!

Seems to be a Dell laptop and charger problem.

June 30th, 2020 00:00

@jphughan Thank you. The one device I linked to seems to be 100 watts and it lists the Mac book Pro and some 15" laptops, and Dell Inspiron and Latitude laptops. The second quotes 60 watts output with the reduction due to the what the dock uses. If I buy a charger which delivers something over say 70 watts, that should then supply the dock and the laptop whichever I use (maybe better to utilise the higher wattage and buy a 90 + charger?), my query was more will a generic charger work, and Dell laptops don't require a Dell dock, it's a standard they should all adhere to?

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June 30th, 2020 07:00

@Smeg Head  Dell laptops that support being charged over USB-C support that using the industry wide USB Power Delivery standard.  But it seems that they do place limits on third party USB-C power sources, for reasons that aren't clear.  But yes, they do work, at least up to 65W (or the max that the system uses if lower, such as the XPS 13 that only uses 45W anyway).  I personally have USB-C power sources from Anker, Nekteck, and Satechi with outputs ranging fro 60-90W, and my various Dell laptops work fine with all of them -- again, up to either 65W, the charger's max output, or the system's max draw, whichever is lowest.

As to the devices you linked, the one that only passes up to 60W might not be because it's account for skimming losses from a higher wattage source.  60W is a fairly common maximum limit to see with USB-C cables because it corresponds to 20V (current max of the USB PD spec) at 3 amps.  Currently, there are two "classes" of USB-C cables, namely those rated for up to 3 amps (60W) and those rated for up to 5 amps (100W).  Cables that support the latter need to include an "e-marker" chip to advertise that capability.  So I suspect that the 60W limit in the case of that adapter relates to its permanently attached cable.

As for a Dell dock, certain Dell systems like the XPS 15 are designed for 130W power sources, and Dell did something proprietary with systems like that as well as certain docks in order to send that over USB-C/TB3, stretching past the 100W max of the official USB PD spec.  So if you want that, you'd have to use a Dell dock.  And then Dell also has a WD19DC dock that plugs into two USB-C connectors on a system in order to provide up to 210W in order to properly support laptops that have even higher power requirements.

August 6th, 2020 21:00

Hi there,

A GREAT piece of information and well written – MANY THANKS.

I will be purchasing the new Dell XPS 13” clamshell later this year when Dell releases it with the new Intel 11th Gen CPU “Tiger Lake” assuming Dell go with Intel !!!

Like the current model Dell XPS, I am also assuming it will come with 2 x Type-C Thunderbolt ports and the device will be rated at 45 watts.

I am looking for two separate Hub/Docking solutions and one additional power supply.

Solution1 - An immediate hub purchase to go with the new XPS. This hub needs to connect all the peripherals listed below and would also be used as a travel solution. This solution would be a temporary solution until Thunderbolt 4 Hub/Docking Stations will hit the market place sometime later.

Solution 2 - Thunderbolt 4 Hub/Docking station when they become available. This is mostly likely to be the Dell WD19TB, but a Thunderbolt 4 version. This hub needs to connect all the peripherals listed below

Regarding Solution 1:  When writing this, what seems to best suit my requirements is an “Anker 8 in 1, 10Gbps Data Hub Model A8383”.   However its power specifications states:  “The USB-C port supports pass-through charging up to 100W (minus 15W for operation), allowing you to charge up your laptop at high-speed while retaining full function of the hub’s other ports.” 

Peripherals to be Connected: Other devices to be run through the “Anker 8 in 1, 10Gbps Data Hub Model A8383” that would be connected to the new XPS 13” “Tiger Lake” processor include:

  • Dell Monitor U2718Q – External screen connected full time via a DP1.4 or HDMI connector.
  • Samsung Galaxy S10 5G phone – Occasional syncing with Outlook on XPS. Use USB Type-C connector.
  • External hard drives for backup purposes – 3.0 Micro B connector. Might use “the other XPS TB4” port.
  • USB Memory sticks – USB Type-A connector
  • SD Card
  • Ethernet – RJ45 connector. Full time Ethernet cable connection to modem/router.
  • Dell Sound bar AC511M, CN-0XFDH2-71623-93B-2195 – USB Type-A. Full time connection

So based on the above power specification and your great article and wanting to buy an additional power supply to be used with the XPS 13” connected to the  “Anker 8 in 1”, what Dell power supply should I buy?

1) Dell USB-C Power Adapter Plus Slim – 45-Watt with USB port. Manufacturer Part Y91PF, Dell Part 492-BBWZ,    Dell Order Code P4516wsap

2) Dell Adapter 65-Watt Type-C with 1M Power Cord, Cus Kit Manufacturer Part 9FNYW,  Dell Part 492-BCBI,   Order Code 492-Bcbi | Dell

3) Dell USB-C Power Adapter Plus 90- Watt - PA901C,   Manufacturer Part 6WX94,   Dell Part 450-AJML

4) Some other Dell USB-C Power Adapter

I hope I have given you enough information. Please let me know if you require other details.

Very much looking forward to your recommendations and please do correct any of my incorrect understanding.

Mark Dent

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August 7th, 2020 13:00

@shiraz2many  Glad you found my post useful, and thanks for the kind words!

In terms of your travel solution, right off the bat if you plan to run a 4K 60 Hz display through a travel hub, you have to make sure the hub itself supports DisplayPort 1.3 or better over USB-C to get that signal out of the system. Most products on the market right now only support DP 1.2, which will limit you to 4K 30 Hz on displays attached through the hub, even if your system supports DP 1.4. The Dell DA300 adapter supports DP 1.3, but I don’t think it has enough other connectivity for your purposes. (Or you could connect the display directly to one of the other USB-C/TB3 ports on the system.)

In terms of power sources, the fact that you’ll be using a system that will likely only require 45W definitely simplifies things, since even if the hub “skims” 15W for itself, that means you still only need 60W total from the source. But since USB-C is only going to become more universal as a power delivery mechanism, I personally would go with the highest wattage power source you can find that is still an acceptable size and cost for you. And there’s no real reason to limit yourself to Dell here, since USB Power Delivery is an industry standard. If you needed 130W over USB-C, then you’d be stuck with Dell, but ironically their 130W adapter isn’t great as a universal option since it only supports 5V and 20V output, not 9V and 15V as are commonly used by some devices for fast charging.

I personally just bought a RAVPower 90W dual port USB-C charger here. It uses new GaN (gallium nitride) technology that allows it to be much smaller than traditional power sources of the same wattage, and it wasn’t very expensive. It can also split its 90W output across its two ports in multiple ways, namely 90/0, 60/30, and 45/45, so it’s a great all purpose charger.

And if you want a great multi-purpose charger for travel (when we can do that again...), look at the Satechi 75W Dual Type-C travel charger here or the 108W Pro version here. You get a 60 or 90W Type-C port, an 18W Type-C port (enough to fast charge an iPhone) and two USB-A ports with 10W total max output. That single charger covers me when I travel since I can charge my laptop, phone, watch, and one other thing all from that single device. And the “one other thing” is either a USB power bank or headphones, neither of which need to be charged every night like the other 3 devices. It is awesome.

August 8th, 2020 20:00

Hi there,

New to all this so not sure how to address people (sorry)

 Re Travel – Understand/agree with your comments but this is not an issue as for when I am travelling I use the XPS’s screen

  • Re Power Sources - Understand/agree with your comments – Thank you.

 Kind Regards 

Mark Dent

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September 14th, 2020 12:00

This is a great write up and addressed a number of my questions regarding dell's handling of USB-C charging. I am curious to know if you're aware of whether or not the 65w max pd with third party devices affects all of their laptops that are rated for higher pd or if there are only some. I just purchased an alienware laptop which now supports USB-C charging but dell makes no mention of its rated pd. Obviously if I can I'd like to get as close to 100w if possible but if it's going to be hampered by the same 65w limitation then there's no reason to spend extra money. Thanks for your help! 

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September 14th, 2020 13:00

@cshelt  Happy to help, glad you found it useful!  The only system I've seen reports of pulling higher wattage from third party USB-C sources has been the XPS 15 9500, where users have confirmed being able to use up to 90W.  I'm not sure if 100W would be possible since I don't remember seeing anybody test a 100W source.  I would also bet that the XPS 17 9700 would probably have the same charging limitations as the XPS 15 9500, but I can't know that for sure.  And I certainly hope that this is a sign of things to come with Dell laptops overall, since this 65W limit seems arbitrary and certainly aggravating.  As for your Alienware system, I'm actually surprised it supports charging via USB-C at all, given that all modern Alienware systems to my knowledge are designed for WELL more than 100W, or even the 130W that Dell stretched the spec to deliver over USB-C/TB3 with certain systems.  I know that at least the early Alienware systems that incorporated USB-C/TB3 didn't support charging from that port at all, I figured for this reason.  But even if that has changed, I wouldn't recommend using a USB-C power source while actively using the system.  If you have an Alienware system designed for 180W, 240W, 330W, or the Area-51M that's designed to have (I think?) both 330W and 180W power supplies connected simultaneously for max performance, then even at 100W you'll be giving your system far less power than it's designed to have available, so you'll likely see slower battery charging, reduced performance, and possibly continued battery drain.  If you'd only want to use that type of power source to charge the system overnight while it's asleep or powered off, then that would very likely be fine, but I wouldn't rely on it for anything beyond that.  Sorry I don't have more detailed information for you though!

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