Precision 5550 Docking Quesiton

@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.

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.

@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!

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!

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.

@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!

It all makes sense perfect when you explain it!  I think you've answered every power adapter/dock question I could imagine.

You are a terrific resource and I can't thank you enough for all your help and responsiveness. 

Take care, be well and thank you again.

@Assistance Appreciated  Happy to help, and glad you're feeling better about your setup!