According to its specs, the topmost port’s supported outputs are 5V==3A / 9V==3A / 15V==3A / 20V==5A / 28V==5A, with the port below that supporting 5V==3A / 9V==3A / 15V==3A / 20V==5A, dropping the 28V==5A tier.
I couldn’t find any specifications regarding supported charging modes aside from the “240W Charging” bit on the expansion card page linked above, so I’m flying blind here. To be fair, I also couldn’t find any such specifications for my MBP, but that charges off any of the chargers I have here just fine, no matter which of the two cables I use.
The problem I’m experiencing is that if I plug my FW16 into the 140W port using the 140W cable while the FW16 is turned on, it will refuse to charge, instead blinking the orange charging LED and making the OS switch between charging and not charging states in roughly 1-second intervals. Since this happens on both Windows and Fedora, I assume the choice of OS is irrelevant and the only important part is that the laptop is turned on and actively consuming power.
If I use the Apple cable instead, the FW16 happily charges at roughly 100 watts.
If the FW16 is turned off, both cables work just fine, but according to my USB-C power meter, it charges at a measly 20 watts, which is weird.
I assume this is a USB-PD thing, so why doesn’t the FW16 just charge at 100W over the 140W cable if it can’t handle the 140W mode? It can clearly charge at 100W if I use the 100W cable, even when connected to the 140W port so I don’t understand why this is happening.
Is there a comprehensive list of supported charging modes? Why does the FW16 charge at a massively reduced rate while turned off?
Are you able to check this cable with another device? The cable may be bad. High wattage USB-C cables have chips in them that are supposed to confirm that they can handle high wattages. If it’s sending bad or garbbled communication then the laptop might be retrying.
What was the battery percentage when this happened? Li-ion charging is not done at full tilt / maximum all the way through. At the low and high end it’s done at a lower rate.
What USB-C meter do you have? It might be interfering with PD communication or just not allow PD speeds.
When the laptop is powered on, USB-C PD is providing power to charge and power the system at the same time. When off, it’s just charging according to it’s li-ion charge profile.
Both cables charge my MBP just fine. It’s my understanding that it would complain if anything about the charger or cable was out of whack, rather than silently continue charging at a lower rate.
Above 90%. You’re probably right about this.
It’s some cheap gizmo from Amazon, but it hasn’t led me astray yet. I don’t think it interferes with PD communication.
Fair enough. A couple of months ago I was setting up a handheld linux thingy that only ever charges at 5 watts when turned off because the charging system wasn’t set up right by the manufacturer, so just kind of assumed the same thing here.
I’m afraid not. It seems the USB-PD spec doesn’t require general helpful information or even the specifics of errors to be provided to the user. The chip that handles PD knows, but the spec doesn’t say it has to pass that on, so they don’t.
Imo, it’s a significant oversight since it leads to poor user experience & frustration. You don’t have any idea why a device isn’t functioning as expected. Bad cable, bad power supply, malfunctioning device, just an accidental mismatch (one part not supporting the speed you want)? Who knows. I understand not providing detailed information for every device, but a laptop or cellphone with a color screen and an advanced OS? The PD spec should require at least error information to be provided if the device maker wants to claim USB-IF compliance. Devices can and do use USB without USB-IF compliance, they just can’t say they’re compliant. And big time manufacturers would like to claim compliance if possible, so it’s a little push towards what you’re supposed to do.
Also note that when the laptop is off, the numbers you’ll see on a wattage tester might not be what some expect. 140W? Never. Even at the fastest part of the li-ion charge profile, when the laptop is off.
Around 1C is the usual rate for normal li-ion batteries to charge at, if you want to be safe & also not wreck its lifespan. I believe I saw FW staff say 1C is what the FWL16 does. For the currently shipping battery, this would equal 85W. Depending on where your meter is connected, you might see a little higher, as you might also read conversion losses. Again, for others that might read this in isolation, do keep in mind that the 240W that the FWL16 supports is for powering the system, a potential high power GPU, devices connected to the USB ports, and then what’s left over to charge the battery.
True. The usb-pd chips in all laptops are terrible with no debug facility. If they could capture the CC1/CC2 messages together with volts/amps this would be far simpler to fix. As it stands, expensive external test equipment is needed instead which greatly limits the amount of users that can help providing useful debug logs.
That being said. I don’t think FW are particularly focused on improving usb port compatibility. I asked FW support for any test evidence they have against the usb spec, and they have none.
You’d be talking to customer service, they’re unlikely to have whatever engineering data you might ask for. Nor would they be likely to be authorized to judge what is ok to release. That’s not the same as “they have none” which to me sounds like suggesting FW did no testing, which is quite impossible.
The user in that thread shows a test against the usb pd spec failing.
So this would imply that FW did not carry out the tests against the usb pd specs.