So if you have the Lenovo power supply and you have a docking station, why not just connect it up and ask the Librem 5 what it is getting? With the supplied charger, the Librem 5 reports PD negotiation of 5V 3A max.
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So I should run
sudo cat /sys/class/power_supply/max170xx_battery/uevent
?
First, thank you @Hristo for asking very qualified/related question (as made my older brain awake) and as second (and equally very important) thank you @irvinewade for getting/posting here your qualified/related answer:
As third I’m already very tired for today but needed to post at least above screenshot (×2):
- SB-AC16-TCUS, USB-PD Type-C 5.0V/3.0A, 15W, DCP based power supply, directly charging L5;
- Anker A2029, USB-PD Type-C, 60W, DCP based power supply, directly charging L5;
- PD-014, USB-PD Type-C, 18W, distributed power supply, directly charging L5;
- AENZR AZ2406, getting power from SB-AC16-TCUS (15W) power pass-through toward L5, all good (post #15 in this thread);
- AENZR AZ2406, getting power from Anker A2029 (60W), power pass-through toward L5 is not usable 0.4790A (not good at all);
- AENZR AZ2406, getting power from PD-014 (18W), power pass-through toward L5 is not usable 0.4790A (not good at all).
Yes, 5. and 6. are having red LED light on but in terms of L5 battery actually meaningless (IMO). Yet, I do think that this is a great finding anyway. Therefore thanks on both of you repeatedly! @Hristo, now is your turn again, please explain what you actually discovered for all of us here (relating to your recent posts). My hint would be: 1500000 (marked green within second screenshot above):
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I just did the measurements. Here the results:
- I tried 3 different phone chargers capable of delivering 5V 3A (Purism, Sony, and Samsung). All 3 negotiated 5V 3A.
- I tried the 65W charger of the Lenovo notebook which is designated as 5V 2A, 9V 2A, 15V 3A, 20V 3,25A.
Surprise. The command returned negotiated 5V 3A even though the power supply states 5V 2A. It would be interesting to measure real consumption under max load to see if it really goes above 5V 2A. I don’t have instruments to do the measure.
- Then I used the following docking station:
https://www.amazon.de/dp/B09Q5SRZTD/
I tried all 4 power supplies from above through this dock and Librem 5 showed in all 4 cases just 5V 0,5A
- Then I tried the Lenovo Thinkpad Hybrid USB-C with USB-A dock Type: 40AF. This dock has its own non USB-C power supply 20V 6,25A.
Librem 5 showed negotiated 5V 3A but unfortunately display signal is not working. Maybe it is due to the sticker “Display Link”. Really a pity because this docking station would have been perfect if displays were working as it has plenty of USB ports and both HDMI and DP ports so it would have been really convenient.
Conclusion:
The huge Lenovo docking station with 20V input can indeed negotiate 5V output. But it is also much larger than the pocket docks we discuss in most of the cases and I am not sure if they also have the possibility to convert the voltage from 20V to 5V.
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In short (while someone already waiting for me), please try the following combo with your Librem 5 (only 5V/2.4A or only 5V/3A power supplies should, as I’m expecting, charge Librem 5 connected to the compliant docking station up to more than enough/adequate 5V/1.5A , while no other voltage negotiated, as only 5V present):
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Another observation.
I have a display that accepts either HDMI or USB-C as video input.
When I connect Librem 5 directly to this display via USB-C to USB-C, the display works. 
When I use any of the 2 docks in between, the video does not work.
(Librem 5 - USB C USB C - Dock - USB C USB C - Display)
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I think that might be expected. If the dock has HDMI out then I think it will forward the video to HDMI when the input USB-C is in DisplayPort altmode. Of course I could be wrong. You could find a dock that has enough functionality to forward the video via a USB-C output. However it is not only about the dock’s handling of video, it is also about how the dock reports things to the host.
If you want to investigate then you will need to use lsusb with a non-working dock and with a working dock - and for us you will need to clarify whether the docks have HDMI out.
As I understand it, with the present charging settings, you will struggle to draw much more than 2A anyway. While a USB-C power meter would be the right equipment to measure for sure, you may not need it.
If the negotiation is for 3A max but in reality it is limited to 2A and you can force the draw to exceed 2A then I guess something will be observable on the Librem 5 i.e. either something bad happens due to insufficient power (shutdown? crash?) or battery charging will be limited (which you should be able to see with the right cat /sys/... incantation).
Check POWER_SUPPLY_USB_TYPE to see whether you got PD or C (or something else).
500 mA, as the standard USB 2.0 maximum, is what you will get when connected to a vanilla USB port that does not have PD (or does have PD but negotiation failed).
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Regarding overheating while charging: can you help to mitigate this issue by limiting the amount of current during charging? IE: 5v @ 500 mA? What is the lowest amperage that the phone needs to successfully charge?
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For me this makes no sense because Librem 5 can work without battery if it gets enough power. So for me the goal is that it runs without using the battery when in convergence mode. If the battery is kept charged and bypassed then the battery will heat less than if it constantly discharges/charges, or am I wrong?
This is also my motivation why I want to get as much as possible power through the dock to Librem 5. So that it gets enough without having to suck from the battery.
I think you might have misunderstood. I am asking about the lowest possible voltage to charge and still use the device.
Charging with high voltages and amps directly correlates to heat. That is how power regulation, etc. works.
I would rather trickle charge overnight, and not overheat doing it, than overheat during a more rapid charge.
I’m asking if such a thing is feasible.
I am definitely curious to learn about the consumption of Librem 5 if you want to run it without any limitations and without a battery. But honestly I doubt that it consumes so little energy.
Raspberry Pi 4 requires a 5V 3A power supply and when using less power you get a warning message, that the system gets too little power and this could cause data loss.
Do you believe that Librem 5 with LTE modem and WiFi is going to consume 6 times less or even twice less? I doubt it. But this would be very very very interesting to find out.
I have no idea how much the SoC and additional components consume, hence why I am asking here.
It is also why my question is still a legit one. Hope that makes sense.
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Take the battery out? 
I think if you want to prioritise running the device and not charging and the battery level is low enough that it would charge if the Librem 5 is receiving power from the USB-C port then you would have to override the default behaviour with magic incantations.
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Let us say I take the battery out and use a dock set-up that delivers 5V 1,5A like the maximum achieved in the tests of Quarnero. Will Librem 5 warn me that it does not get enough before some damage / data loss occurs?
I don’t want to damage the device.
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I don’t know but I doubt that any damage would occur. 1.5 A should be more than enough to run the device anyway.
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How do you judge that 5V 1,5A would be enough?
I compare it with Raspberry Pi 4 in my head.
Librem 5 has a display while RPi doesn’t.
Librem 5 has an LTE modem while RPi doesn’t.
Librem 5 has a WiFi module that is not part of the SoC and is more capable than the built in WiFi of the RPi which does not necessarily means that it needs more power, but I GUESS it needs.
At least because of these 3 factors I would GUESS that Librem 5 needs more juice under average load and under full load compared to average load and full load of RPi4.
It would be nice if we had an official statement on what is sufficient for running Librem 5 without a battery and for example for a hot swap of the battery.
On the other hand, the raspberry pi has a bunch of ports and pins it has to provide power to that the L5 doesn’t. It isn’t out of the question that it would require more power.
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You are having right as, IMHO, having lower voltage and lower amperage during charging keeps overheating down (actually there is none). 4.8V/1400mA might serve as some orientation, especially when battery already above 50% (anything negotiated above 5.00V I actually and simply do not use), therefore I’d recommend using power supply (or power bank) providing 5.00V/1700mA, at least (actually cannot confirm or have no evidence that more than 5.00V/1900mA needed with the Librem 5, for any usage, although I recall seeing bursts with over 2.1A). With screen off (please note that Wi-Fi is not on, not consuming any power, therefore it is already achievable to have Librem 5 on standby with under 5.00V/0.2A, another guess of mine as just do not have time to proof this, but things are already looking good to me anyway):
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