Precision 5550 Docking Quesiton

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Hi:

I recently purchased a MDell Precision 5550 laptop and have a USB docking station from a previously owned Precision 5520.  The docking station does not have a USB C input, so I am unable to connect the 5550 to the docking station.  The 5550 was shipped with a 130W power source.  I have a 180W power source I have been using with the 5520 which will connect to the USB docking station.  Can I use the 180W power source in the USB docking station and connect the docking station to the 5550 using the USB C output from the docking station?

Thanks in advance for any help.

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Re: Precision 5550 Docking Quesiton

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@Assistance Appreciated  Ok, that helps.  But the WD15 is a USB-C dock, so its USB-C "input" would be the cable attached to the side of the dock with a USB-C connector on the end that's meant to connect to your laptop.  So I'm not clear what you mean when you say that the WD15 doesn't have a USB-C "input".  Do you mean a USB-C output in order to connect a USB-C display or something?

In any case, the WD15 180W w/ 130W passthrough you have will be fine with your Precision 5550.  The WD19TB 180W w/ 130W passthrough when paired with your 5550 would be able to tap into 4x more video bandwidth than the WD15 and therefore can run higher-end display setups than the WD15.  The WD19TB can run dual 4K 60 Hz displays or triple QHD, whereas the WD15 is limited to dual 1920x1200 displays or a single QHD 60 Hz display (or single 4K but only at 30 Hz).  But if that's not an issue for your setup, then the WD15 should still work completely fine because the 180W power supply you're using will allow it to pass up to 130W to attached systems, and that's what the Precision 5550 is designed to have.  Enjoy!

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Re: Precision 5550 Docking Question

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@Assistance Appreciated  Happy to help.  Yes, a 130W power supply connected directly to the system will work perfectly fine.  But the dock has to reserve some of the power supply's capacity to run its own internal electronics and also to power any USB peripherals you might decide to plug into the dock, so it can't pass through 100% of the power it's receiving.

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Re: Precision 5550 Docking Quesiton

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@Assistance Appreciated  What exact docking station model do you have?  The only docking stations that could have connected to your older 5520 would have been USB-C/TB3 docks that would plug into a USB-C port or a USB-A "regular USB" dock.  You say that this dock doesn't connect via USB-C/TB3.  But if it connects via USB-A, then it wouldn't make sense to have a 180W power supply plugged into it, because docking stations cannot provide power to systems over USB-A.  That's only possible with USB-C.  I'm also not sure what you're talking about in terms of USB-C inputs and outputs on the docking station.  You cannot plug a system into a USB-C peripheral port.  But if your dock has a USB-C peripheral port, then it likely has a way to connect to a system via USB-C as well.

Again, providing the dock model upfront would have been very useful.  As a general piece of advice, when asking for technical assistance, it helps to provide basic technical information so that the people here who are willing to help have something to work with.

Re: Precision 5550 Docking Quesiton

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Hi:

Thanks for your reply.  Sorry I didn't provide the dock model in my original message.  I have the Dell WD15 with 180W which I was using with a Dell Precision 5520.  I decided to connect the Precision 5550 to the WD15 this morning and did not get any compatibility warning and it just completed a full charge.  The WD15 meets my needs and I would like to use it, but didn't want to risk damaging the 5550.

Looks like Dell recommends the WD19TB with 130W power delivery for the 5550, but would prefer to not spend another $300 if not necessary.  Dell indicates the WD19-180W with 130 is also supported for the 5550.

Again, I appreciate your help and apologize for not being more clear in my earlier message.

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Re: Precision 5550 Docking Quesiton

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@Assistance Appreciated  Ok, that helps.  But the WD15 is a USB-C dock, so its USB-C "input" would be the cable attached to the side of the dock with a USB-C connector on the end that's meant to connect to your laptop.  So I'm not clear what you mean when you say that the WD15 doesn't have a USB-C "input".  Do you mean a USB-C output in order to connect a USB-C display or something?

In any case, the WD15 180W w/ 130W passthrough you have will be fine with your Precision 5550.  The WD19TB 180W w/ 130W passthrough when paired with your 5550 would be able to tap into 4x more video bandwidth than the WD15 and therefore can run higher-end display setups than the WD15.  The WD19TB can run dual 4K 60 Hz displays or triple QHD, whereas the WD15 is limited to dual 1920x1200 displays or a single QHD 60 Hz display (or single 4K but only at 30 Hz).  But if that's not an issue for your setup, then the WD15 should still work completely fine because the 180W power supply you're using will allow it to pass up to 130W to attached systems, and that's what the Precision 5550 is designed to have.  Enjoy!

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Re: Precision 5550 Docking Quesiton

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You are The Best!  Thank you so much for taking time to provide such a detailed, informative reply.  I was initially confused when trying to connect the 5550 power source to the WD15 because the 5550 power cord has a USB C connector.  As long as I can use the WD15 with 180 W and not risk damaging the 5550, I'm good.

Thank you again for your help and expertise.

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Re: Precision 5550 Docking Quesiton

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@Assistance Appreciated  Oh ok, now I get it.  You were talking about a USB-C power input.  That's correct, Dell docking stations as of this writing all still use the traditional 7.4mm barrel style connector, including the WD19 family models.  Some laptops still do as well, especially those with higher power requirements, although a smaller 4.5mm slim tip barrel and of course USB-C are gaining market share there.  But it's completely fine to use a 180W power adapter that has a barrel style connector for the dock and then connect the dock to a system that receives power over USB-C -- in fact that's the ONLY way it can work given the design of current docks.  I suspect the reason the WD15 isn't explicitly mentioned as compatible with the Precision 5550 is because by the time the 5550 had arrived, the WD15 had been replaced by the WD19 family models.  But that doesn't mean it won't work, as you've found.  In any case, you are completely fine.  And if it helps set your mind at ease any further, the USB PD spec has measures to prevent nasty outcomes.  The way it works is that the power source (the dock in this case) advertises the voltage and amperage levels it supports providing, and then the device receiving power is allowed to choose from among those options.  This prevents the source from providing power levels that the attached device can't handle and also prevents the device being charged from trying to draw more power than the source is designed to provide.  Very early on in the USB-C days, there were some chargers that were poorly designed and didn't comply with the USB PD spec, which could indeed cause damage to attached device and even pose a fire hazard, but that was years ago now.  Enjoy your setup!

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Re: Precision 5550 Docking Quesiton

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You were talking about a USB-C power input. Yes, exactly!  I will sleep better tonight after reading your posts.  Very helpful and much appreciated.  Thank you again for taking time to explain and educate.  Wish I had found this community a long time ago.  Keep up the good work!

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Re: Precision 5550 Docking Quesiton

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Hi:

I thought I'd try to pick your brain one more time while our conversation was still fresh.  I'm wondering if you'd be indifferent to using the 180W power adapter with the WD15 dock vs. a 130W power adapter?  I have both and was curious if both power adapters were viable options.

I am noticing the Precision 5550 fan is cycling on and off more often than the 5520 I had been using.  I use both the 5520 and 5550 with an external monitor and keep the lid closed, so I wasn't sure of that might be contributing to the fan cycling on.

Thank you again for your time and expertise.

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Re: Precision 5550 Docking Quesiton

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@Assistance Appreciated  If you run the WD15 (or WD19, for that matter) from a 130W power source, then it will only pass up to 90W to the attached system.  If your Precision 5550 has ONLY an Intel GPU and no NVIDIA GPU, that is fine.  But otherwise, that system will be designed for a 130W power source, so if you run it from a 90W source, you will likely see slower battery charging and reduced performance, especially under workloads that use the NVIDIA GPU.  So yes it will work and won't damage anything, but it certainly wouldn't be ideal.  You need the 180W power source in order to push 130W through to the attached system.

In terms of fan cycling, that could be down to different thermal designs and/or firmware tuning.  The Precision 5550 and its sister the XPS 15 9500 were the first major redesign of that chassis after four generations of essentially the same design, so I wouldn't be too surprised at different behavior.  The 5550 might be tuned to try to run silent more often but therefore will have to cycle fans on as temperatures rise, whereas the 5520 might be tuned to keep the fans running quietly more often.  That's purely a guess on my part, but I wouldn't consider fan cycling to be indicative of a problem. Hopefully this helps!

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Re: Precision 5550 Docking Question

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Another very helpful reply, thank you! All makes sense. I was asking about the 130W because that was the power adapter shipped with the 5550. I also received a 130W when I purchased the 5520. I'm guessing it's fine to use the 130W when I am using the laptop while traveling without the WD15 dock. I plan to continue using the 180W with the dock for the benefits you describe. I appreciate your thoughts on the fan cycling and am pleased to learn it's not indicative of any potential issues. Thank you again for your insight and responsiveness. Both are much appreciated.
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