I have a few USB-C PD chargers with built-in Voltage and Amperage gauges. With these, the laptop would negotiate 20 V correctly but then constantly jump between 0.2 A, 1.2 A, 3 A and others. I also noticed generally slower charging. I see the same behavior in Windows. The port doesn’t appear to matter.
I got a universal USB-C PD meter today and have checked many different chargers and it’s been the same. The weird thing is, its only when loaded into an OS, if I just leave it at the BIOS it stays at a near constant 2.3A. I did test some other devices and they’re stable using the same chargers.
Wondering if anyone else has noticed the same behavior. I know there’s been a few posts with similar kernel errors on the Linux side, but haven’t seen anything talking about unstable/jumpy USB-C PD charging rates in general. I do expect there to be some small variation, but not constant large jumps – seems like it can’t properly decide what it should be/needs. If I stress test the upper bound and middle amperage will tend to be higher, but it still wont be stable.
I am fully up-to-date on Windows (including the driver bundle) and also up-to-date on Linux (Arch, kernel 6.14.4-arch1-2).
haven’t seen anything talking about unstable/jumpy USB-C PD charging rates in genera
There are reports for this already. It was first noticed on FW16 and fixed by firmware update. Probably will need firmware update on new boards as well…
For PD Charging, the Charger will tell the laptop which modes it can do.
There are some “fixed” modes, such as 5V, 20V etc. but there is an EPR, or Extended Power Range
The Linux kernel can report the “fixed” modes in “sensors”, but the Linux kernel does not support EPR, so will put things like 5V in the sensors output, when EPR is actually working at 36V or something like that.
In general, the PSU negotiates a Voltage to use, and advises the laptop what the current limit is, and then the laptop can draw anything it likes, up until that current limit.
So, seeing it jump around 0.2, 1.2, 3A is normal if the Laptop was told the current limit was 3A.
The voltage tends to stay fixed at the highest voltage both Laptop and PSU can do, and then it just adjusts the current draw as needed.
I understand that part of PD and expect some variation.
My concern is that even with some load, it oscillates and doesn’t even come close to stabilizing near the upper range. E.g. - say running a stress test, all my old mainboards and other PD capable systems will pull close to the max wattage of the adapter and stay there with some small fluctuation…but with this HX 370 it’ll just flipflop and tend to stay at lower wattages. This is consistent across all 60/65/100W adapters I’ve tested.
I am aware that at high load it will use the battery to supplement, but even with lower loads the battery doesn’t consistently charge and higher loads it seems to mostly ignore the AC adapter – battery discharging significantly and in-line meter reading ~10-20W on average.
I did put my 7840u back in the chassis and do similar tests and it does what I expect: Under load, it will use what the power adapter offers. There will be some fluctuation of course, but it stays at a high wattage. Similar behavior to both Windows and Linux and multiple adapters.
Anyway, I was hoping to find someone else testing with an in-line meter like mine and seeing the same or not since this is the only PD device I have with this behavior. I did see I missed a longer post in the Batch 1 thread where someone did mention using a meter and seeing it use the full wattage (unlike mine)…so now thinking it might actually be an issue with my board.