XPS 15 9550 130W USB-C Being Detected as 60W

@DaveKerk  I work in IT, so I've seen many more than my fair share of the "Unknown" adapter issues.  When they happen, the most likely culprit are, in descending order:

• The charger
• The DC jack (if it's a separate part)
• The motherboard

Obviously a motherboard replacement would be much trickier than what you've done thus far, and harder to source as a part especially if you want a "fresh" one that allows you to set a Service Tag as opposed to one that came out of a system that will have a fixed Service Tag, since that is a write-once field.  But based on what else you've already replaced, I don't think there's anything else that would get 130W charging from the barrel-style chargers working again.  And unfortunately if the 130W charger can't be fully utilized on that system and the system limits itself to 65W on non-Dell chargers, that significantly limits your options.  But I can think of two alternatives short of a motherboard replacement

• Get a Dell dock that supports providing 130W over USB-C/TB3, which will work even with the XPS 15 9550 because those docks were created specifically to support the XPS 15 9550 when it was introduced.  The latest docks that support that are the WD19 180W version (not the 130W version, which only passes 90W through to the system) or the WD19TB (comes standard with a 180W power source).  The main difference between the two is the display setups they can run and the fact that the WD19TB has a "downstream" TB3 peripheral port.  I can go into more about this if needed.  But of course a dock won't help you when you're away from the dock.  For that....
• ...short of a motherboard of a replacement, you might be able to split the difference between the non-Dell 65W cap and the 130W you can't achieve by trying Dell's own 90W USB-C charger here.  Obviously it's not 130W, but since it's a Dell charger, the system might actually draw 90W from it, which would be better than the 65W you'd be stuck with otherwise.  But full disclosure, I'm not actually certain the XPS 15 9550 will in fact draw 90W from that charger.  I just know the charger exists, so I thought I'd suggest it.

@jphughan I appreciate the input. While I have you, I might as well ask, the reason I am even going for a USB-C charger is because the normal barrel style of charger stopped working. I have replaced the charger, the battery, and the DC jack itself (all with genuine OEM parts) and the BIOS just says unknown whenever it's plugged in. Thoughts?

The USB-C charger is also a genuine OEM, so I would imagine that it would detect and charge at max (should this old of a system support it, which I cannot find any solid answer on).

The cable between block and port is sealed into the block. So there's no choice for which USB-C cable to use. It would be unfortunate that it would only use the 60W. It's an i3 system with no dGPU. Do you think it will suffer much impact from 60W? And if it will only accept a 60W, should I just purchase a 60W charger and return the 130W?

@DaveKerk I've only used XPS 15s that have an NVIDIA GPU, but my experience is that a 60W power source might be fine as a travel charger if you'll be using it primarily to charge the system overnight while it's powered off, but it's not a great solution as a power source for when you're actively using the system.  60W is less than half the amount of power the XPS 15 is designed to have available, so when that's all you give the XPS 15, it will respond by reducing it battery charging speeds and its CPU and GPU performance.  Under extreme loads it might continue to drain the internal battery even while connected to power in order to make up for the shortfall, but that's a last resort.  It will take steps to reduce its power consumption even at the cost of performance first in an attempt to operate "sustainably".

Even more annoyingly, Dell laptops in general as of this writing limit themselves to drawing no more than 65W from any non-Dell USB-C power source, even if the power source supports more and the system would benefit from more.  I have no idea why Dell has this seemingly unnecessarily and arbitrary limitation, and the impact is particularly significant on relatively high power systems like the XPS 15, but I've seen this behavior on multiple laptops with multiple third-party chargers.  I hope Dell rethinks having this limitation at some point.

But if all you can get is 60W, then yes I'd return the charger.  There are lots of less expensive and physically smaller 60W chargers available from solid companies like Anker and Aukey, among others -- especially now that GaN (gallium nitride) chargers have arrived on the market.  Another reason to consider switching is because I also remember reading that Dell's 130W charger only supports 5V and 20V output, which means that despite its high wattage output, it can't actually be used as a fast charger for devices that require 9V or 15V for fast charging, such as many recent smartphones and tablets.  Instead, if the device charges at all, it will only be at 5V "regular USB" speeds, not USB PD speeds.  Most USB-C power sources on the market support 5V, 9V, 15V, and 20V.

@jphughan Gotcha, that is very weird to me. I'll have to see the prices and see what they want to do.

I very much appreciate all the help you've given, definitely learned a lot!!

I think that will be the end of this thread then.

@jphughan So I'm a bit lost with one part, the USB C charger is not a non-Dell, it's an official Dell 130W USB-C. I would prefer not to do a motherboard replacement just since the part alone is between $400 and $600. And for a 6th gen i3, it's very not worth it. I will talk to the person I'm fixing this for and see if they want to spring for an expensive dock, but are sure you that it will charge the full 130W? 

@DaveKerk  Happy to help.  Just as one more data point if it bolsters your confidence or the confidence of the owner of this system, there's this PDF about dock compatibility with various systems.  But there is a catch.  Where the PDF says "XPS 9530", it's actually supposed to say "XPS 9550".  The XPS 9530, which is the immediate predecessor to the 9550 (there was never a 9540) doesn't have a USB-C/TB3 port at all, so it wouldn't be compatible with any of these docks -- and the 9550, which does have a USB-C/TB3 port, isn't listed at all.  I pointed this issue out to a Dell Support rep that has been helpful escalating issues internally in the past, and he replied that the Documentation team is aware of that error and will fix it in a new revision, but they have no ETA.  I had also previously pointed out other errors in that PDF around certain XPS 13 models incorrectly being indicated as incompatible with the WD19 130W even though they were in fact compatible, and they acknowledged those errors as well.  But if it helps reassure you, I figured I'd send it.