Hi maeffjus,
We may actually agree more than you think. I (wrongly!) assumed you might not know much about electronics. We both know how assumptions sometimes turn out, hopefully this one wasn't catastrophic ;-) I'm sorry. I won't oversimplify anything in this post, my point should be clearer.
First, I apologize for the confusing "we". I've often been on the receiving end of such conversations, and I sometimes (often?) forget that's not the case on this forum. No, I don't and haven't worked for Lenovo and never had an affiliation with them, but I did work in other computer shops. I will try not to do it again, and I did edit the previous post earlier because I had used "we" again.
For the next part, I'm going with some known facts:
- I agree that lugging around a big 170W adapter (~1.25" x 3" x 6", 21.5"³, 1.32lb) is annoying for a mobile device,
- That's 1/5th the weight of the P52 (or less),
- It's over the average power use of the laptop in most cases,
- The P52 must run fully loaded with it, but sometimes it cannot (170W not enough for all ports when loaded),
- The Slim Tip adapter power availability is known by the machine (ID pin with resistor),
- It's even worse with the newer models, some are using 230W adapter (~1" x 4" x 8", 29.5"³, 1.71lb),
Possibly facts (from memory, I read so many posts, I could have mixed a few):
P5x models previous to the P52 could:
- Use airplane power, (P52+ just ignores external power and runs on battery),
- Be powered from USB-C, even in a limited way,
And I thought that the P52 could run with a smaller PSU on Slim-tip, compensating with the battery. If it doesn't, well, that's sad! Anyway, Specs of smaller power adapters:
- 135W, ~1.25" x 2.5" x 5.75", 17.25"³, 1.1lb
- 90W, ~1.25" x 2" x 5", 11.53"³, 0.79lb (roughly half the size and 0.5lb less than the 170W one)
Now, I agree the electronic limitations are not unsurmountable. I think the CPU can be reconfigured (I know about TDP btw ;-) ), and likely the dGPU too. The EC should be capable to manage all this. Why Lenovo does not do so, yes, that's speculation. Call it an educated guess, but a guess. I'd like to know for sure. Certainly not easy to explain to someone not familiar with electronics.
One possibility is software: Microsoft has trouble delivering good Windows 10 updates, and their PC business is a mess. Combined with the 2-versions-a-year cycle, it causes much hair loss in IT departments. They keep moving the target for the sake of it. Just think about their power slider idea! Lenovo had something better, but not any more! Of course, that does not explain why the new Lenovo Vantage has so many missing features. At least, they made the old v3 available as the v20 "Enterprise" version!
Now, my understanding of USB-C PD is that it's primarily to power accessories. The P52 simply cannot feed 100W/port with the 170W adapter, but then, few will need to do so. As for why the P52 cannot take power IN, again, there is only speculation. I don't mind much as I don't have any USB-C devices anyway, but one day I will! My opinion might change then. Still, I chose to get the P52 instead of the P53 because of USB-C (I need USB3-A right now).
BTW, I'm sure you know Intel can strong-arm manufacturers, and they have made mistakes they tried to hide in the past. Up to recently, the P52 memory ran at 2400MHz instead of 2666MHZ, "Intel limitation" (now fixed in BIOS). There was this: Critical Intel Thunderbolt Software and Firmware Updates - ThinkPad , "These symptoms may occur after 6 to 12 months of typical usage". There was the "secret" recall of the Intel Atom C2000 processors with faulty clock outputs, used in network devices, which was under some kind of NDA. There was the flawed cable modem processor that caused huge latency spikes, as well as many others. How this ties in the P52? Maybe the missing PD-in is another "Intel limitation". But that is only speculation too!
I hope you can find a power source appropriate for your use case! You have the skills to jerry-rig an USB-C PD-in adapter board (quick search: https://www.electronics-lab.com/usb-pd-stand-alone-adapter-board-oxplot/) to Slim Tip. I'd try that, and you can test with the various resistor IDs to find one the P52 likes. Hopefully it will work with the 90W ID!
Good success!
Martin