One of the problems I encountered with the PinePhone Pro (PPP) when I tried using it as a daily driver [1] was the charge speed, both slow charging and a bad ratio of charge speed to discharge speed. I also tried using a One Plus 6 (OP6) which had a better charge speed and battery life but I never got VoLTE to work [2] and VoLTE is a requirement for use in Australia and an increasing number of other countries. In my tests with the Librem 5 from Purism I had similar issues with charge speed [3].
What I want to do is get an acceptable ratio of charge time to use time for a free software phone. I don’t necessarily object to a phone that can’t last an 8 hour day on a charge, but I can’t use a phone that needs to be on charge for 4 hours during the day. For this part I’m testing the charge speed and will test the discharge speed when I have solved some issues with excessive CPU use.
I tested with a cheap USB power monitoring device that is inline between the power cable and the phone. The device has no method of export so I just watched it and when the numbers fluctuated I tried to estimate the average. I only give the results to two significant digits which is about all the accuracy that is available, as I copied the numbers separately the V*A might not exactly equal the W. I idly considered rounding off Voltages to the nearest Volt and current to the half amp but the way the PC USB ports have voltage drop at higher currents is interesting.
This post should be useful for people who want to try out FOSS phones but don’t want to buy the range of phones and chargers that I have bought.
Table of Contents
Phones Tested
I have seen claims about improvements with charging speed on the Librem 5 with recent updates so I decided to compare a number of phones running Debian/Trixie as well as some Android phones. I’m comparing an old Samsung phone (which I tried running Droidian on but is now on Android) and a couple of Pixel phones with the three phones that I currently have running Debian for charging.
Chargers Tested
HP Z640
The Librem 5 had problems with charging on a port on the HP ML110 Gen9 I was using as a workstation. I have sold the ML110 and can’t repeat that exact test but I tested on the HP z640 that I use now. The z640 is a much better workstation (quieter and better support for audio and other desktop features) and is also sold as a workstation.
The z640 documentation says that of the front USB ports the top one can do “fast charge (up to 1.5A)” with “USB Battery Charging Specification 1.2”. The only phone that would draw 1.5A on that port was the Librem 5 but the computer would only supply 4.4V at that current which is poor. For every phone I tested the bottom port on the front (which apparently doesn’t have USB-BC or USB-PD) charged at least as fast as the top port and every phone other than the OP6 charged faster on the bottom port. The Librem 5 also had the fastest charge rate on the bottom port. So the rumours about the Librem 5 being updated to address the charge speed on PC ports seem to be correct.
The Wikipedia page about USB Hardware says that the only way to get more than 1.5A from a USB port while operating within specifications is via USB-PD so as USB 3.0 ports the bottom 3 ports should be limited to 5V at 0.9A for 4.5W. The Librem 5 takes 2.0A and the voltage drops to 4.6V so that gives 9.2W. This shows that the z640 doesn’t correctly limit power output and the Librem 5 will also take considerably more power than the specs allow. It would be really interesting to get a powerful PSU and see how much power a Librem 5 will take without negotiating USB-PD and it would also be interesting to see what happens when you short circuit a USB port in a HP z640. But I recommend not doing such tests on hardware you plan to keep using!
Of the phones I tested the only one that was within specifications on the bottom port of the z640 was the OP6. I think that is more about it just charging slowly in every test than conforming to specs.
Monitor
The next test target is my 5120*2160 Kogan monitor with a USB-C port [4]. This worked quite well and apart from being a few percent slower on the PPP it outperformed the PC ports for every device due to using USB-PD (the only way to get more than 5V) and due to just having a more powerful PSU that doesn’t have a voltage drop when more than 1A is drawn.
Ali Charger
The Ali Charger is a device that I bought from AliExpress is a 240W GaN charger supporting multiple USB-PD devices. I tested with the top USB-C port that can supply 100W to laptops.
The Librem 5 has charging going off repeatedly on the Ali charger and doesn’t charge properly. It’s also the only charger for which the Librem 5 requests a higher voltage than 5V, so it seems that the Librem 5 has some issues with USB-PD. It would be interesting to know why this problem happens, but I expect that a USB signal debugger is needed to find that out. On AliExpress USB 2.0 sniffers go for about $50 each and with a quick search I couldn’t see a USB 3.x or USB-C sniffer. So I’m not going to spend my own money on a sniffer, but if anyone in Melbourne Australia owns a sniffer and wants to visit me and try it out then let me know. I’ll also bring it to Everything Open 2026.
Generally the Ali charger was about the best charger from my collection apart from the case of the Librem 5.
Dell Dock
I got a number of free Dell WD15 (aka K17A) USB-C powered docks as they are obsolete. They have VGA ports among other connections and for the HDMI and DisplayPort ports it doesn’t support resolutions higher than FullHD if both ports are in use or 4K if a single port is in use. The resolutions aren’t directly relevant to the charging but it does indicate the age of the design.
The Dell dock seems to not support any voltages other than 5V for phones and 19V (20V requested) for laptops. Certainly not the 9V requested by the Pixel 7 Pro and Pixel 8 phones. I wonder if not supporting most fast charging speeds for phones was part of the reason why other people didn’t want those docks and I got some for free. I hope that the newer Dell docks support 9V, a phone running Samsung Dex will display 4K output on a Dell dock and can productively use a keyboard and mouse. Getting equivalent functionality to Dex working properly on Debian phones is something I’m interested in.
Battery
The “Battery” I tested with is a Chinese battery for charging phones and laptops, it’s allegedly capable of 67W USB-PD supply but so far all I’ve seen it supply is 20V 2.5A for my laptop. I bought the 67W battery just in case I need it for other laptops in future, the Thinkpad X1 Carbon I’m using now will charge from a 30W battery.
There seems to be an overall trend of the most shonky devices giving the best charging speeds. Dell and HP make quality gear although my tests show that some HP ports exceed specs. Kogan doesn’t make monitors, they just put their brand on something cheap. Buying one of the cheapest chargers from AliExpress and one of the cheaper batteries from China I don’t expect the highest quality and I am slightly relieved to have done enough tests with both of those that a fire now seems extremely unlikely. But it seems that the battery is one of the fastest charging devices I own and with the exception of the Librem 5 (which charges slowly on all ports and unreliably on several ports) the Ali charger is also one of the fastest ones. The Kogan monitor isn’t far behind.
Conclusion
Volage and Age
The Samsung Galaxy Note 9 was released in 2018 as was the OP6. The PPP was first released in 2022 and the Librem 5 was first released in 2020, but I think they are both at a similar technology level to the Note 9 and OP6 as the companies that specialise in phones have a pipeline for bringing new features to market.
The Pixel phones are newer and support USB-PD voltage selection while the other phones either don’t support USB-PD or support it but only want 5V. Apart from the Librem 5 which wants a higher voltage but runs it at a low current and repeatedly disconnects.
Idle Power
One of the major problems I had in the past which prevented me from using a Debian phone as my daily driver is the ratio of idle power use to charging power. Now that the phones seem to charge faster if I can get the idle power use under control then it will be usable.
Currently the Librem 5 running Trixie is using 6% CPU time (24% of a core) while idle and the screen is off (but “Caffeine” mode is enabled so no deep sleep). On the PPP the CPU use varies from about 2% and 20% (12% to 120% of one core), this was mainly plasmashell and kwin_wayland. The OP6 has idle CPU use a bit under 1% CPU time which means a bit under 8% of one core.
The Librem 5 and PPP seem to have configuration issues with KDE Mobile and Pipewire that result in needless CPU use. With those issues addressed I might be able to make a Librem 5 or PPP a usable phone if I have a battery to charge it.
The OP6 is an interesting point of comparison as a Debian phone but is not a viable option as a daily driver due to problems with VoLTE and also some instability – it sometimes crashes or drops off Wifi.
The Librem 5 charges at 9.2W from a a PC that doesn’t obey specs and 10W from a battery. That’s a reasonable charge rate and the fact that it can request 12V (unsuccessfully) opens the possibility to potential higher charge rates in future. That could allow a reasonable ratio of charge time to use time.
The PPP has lower charging speeds then the Librem 5 but works more consistently as there was no charger I found that wouldn’t work well with it. This is useful for the common case of charging from a random device in the office. But the fact that the Librem 5 takes 10W from the battery while the PPP only takes 6.3W would be an issue if using the phone while charging.
Now I know the charge rates for different scenarios I can work on getting the phones to use significantly less power than that on average.
Specifics for a Usable Phone
The 57W battery or something equivalent is something I think I will always need to have around when using a PPP or Librem 5 as a daily driver.
The ability to charge fast while at a desk is also an important criteria. The charge speed of my home PC is good in that regard and the charge speed of my monitor is even better. Getting something equivalent at a desktop of an office I work in is a possibility.
Improving the Debian distribution for phones is necessary. That’s something I plan to work on although the code is complex and in many cases I’ll have to just file upstream bug reports.
I have also ordered a FuriLabs FLX1s [5] which I believe will be better in some ways. I will blog about it when it arrives.
| Phone | Top z640 | Bottom Z640 | Monitor | Ali Charger | Dell Dock | Battery | Best | Worst |
|---|---|---|---|---|---|---|---|---|
| Note9 | 4.8V 1.0A 5.2W | 4.8V 1.6A 7.5W | 4.9V 2.0A 9.5W | 5.1V 1.9A 9.7W | 4.8V 2.1A 10W | 5.1V 2.1A 10W | 5.1V 2.1A 10W | 4.8V 1.0A 5.2W |
| Pixel 7 pro | 4.9V 0.80A 4.2W | 4.8V 1.2A 5.9W | 9.1V 1.3A 12W | 9.1V 1.2A 11W | 4.9V 1.8A 8.7W | 9.0V 1.3A 12W | 9.1V 1.3A 12W | 4.9V 0.80A 4.2W |
| Pixel 8 | 4.7V 1.2A 5.4W | 4.7V 1.5A 7.2W | 8.9V 2.1A 19W | 9.1V 2.7A 24W | 4.8V 2.3A 11.0W | 9.1V 2.6A 24W | 9.1V 2.7A 24W | 4.7V 1.2A 5.4W |
| PPP | 4.7V 1.2A 6.0W | 4.8V 1.3A 6.8W | 4.9V 1.4A 6.6W | 5.0V 1.2A 5.8W | 4.9V 1.4A 5.9W | 5.1V 1.2A 6.3W | 4.8V 1.3A 6.8W | 5.0V 1.2A 5.8W |
| Librem 5 | 4.4V 1.5A 6.7W | 4.6V 2.0A 9.2W | 4.8V 2.4A 11.2W | 12V 0.48A 5.8W | 5.0V 0.56A 2.7W | 5.1V 2.0A 10W | 4.8V 2.4A 11.2W | 5.0V 0.56A 2.7W |
| OnePlus6 | 5.0V 0.51A 2.5W | 5.0V 0.50A 2.5W | 5.0V 0.81A 4.0W | 5.0V 0.75A 3.7W | 5.0V 0.77A 3.7W | 5.0V 0.77A 3.9W | 5.0V 0.81A 4.0W | 5.0V 0.50A 2.5W |
| Best | 4.4V 1.5A 6.7W | 4.6V 2.0A 9.2W | 8.9V 2.1A 19W | 9.1V 2.7A 24W | 4.8V 2.3A 11.0W | 9.1V 2.6A 24W |
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