Charging Edge 1040 with USB-C PD chargers ... is it OK?

IDK for a fact, but I'd have to assume it's OK.  The USB charger spec is such that the device being charge decides and controls the charge current and voltage within the capability of the charger.  This spec permits optimal charging and prevents damage.

The recommended charging-setup will give you charging at 0.5A (original cable on a combatible Garmin USB-charger or using an USB-A computer port).

If 1.4A or 1A where OK, why isn't Garmin charging with higher current on their own 2.4A charger or on USB3-ports?

I stick with 0.5A charging until Garim clarifies the supported charging-methods. 

Ok. I think we need to clear things up here as this is a subject people always get confused over.  The ability of the charger should not make a difference.  You could connect a 20A supply up and the device will only take what it needs. The charging capability is the maximum rating, not what it will always put out. The current draw is determined by the device connected.  Now there is an issue which is mostly legacy that people are still thinking applies.  Some devices didn’t have very good charging circuits and could have issues if high capacity chargers were connected. Modern devices should have fixed this now. 

So the device will only take up to what it’s been designed for. I have connected the 1040 up to a PD charger and it charges fine. It doesn’t get hot and charges quicker than the 1030 and 1000. I should stress only use quality PD chargers. Not cheap brands. 

Now the bigger question is should you do this all the time. I’d say yes, but the real problem is constantly charging to 100% and worse leaving it connected at 100%. If you really want to get the most out of your battery only really charge it to 80% unless you need to for a long ride. With the 1040 at 30+ hours - that’s a very long ride. 

I’ll tell you now you will do more damage to your battery leaving it connected for a long time at 100% on a 1.4A battery than you will fast charging it to 80% with a 3A charger. 

I noticed the edge 1040 charging at different wattages depending if it was powered off or not. (Using an anker 543 usb-c -> usb-c cable I saw 4.6w with it powered on and 1.9w with it powered off.

The original garmin usb-a to usb-c cable would only charge at 1w for me.

iheathcock said:

Ok. I think we need to clear things up here as this is a subject people always get confused over.  The ability of the charger should not make a difference

yeah unfortunately garmin has replaced 1040s already from over charging. I've seen a couple of threads on it and also, it has happened to me more than once from my GaN wall charger.

Over USB-C, the 1040 gets too hot to touch at the USB-C port and it stinks like burning electronics.

My GaN charger puts out 80w but the 1040 should not ask for it of course.

I'm certain if the 1040 was plugged in for even a minute or two more, it would have died.

But I can charge it over USB-C using the same cable, to a MacBook Pro, or my Anker 737 power bank.

Since it really doesn't take a long time to charge, I personally only charge over USB-A to USB-C. 

The cable connector (USB-A or USB-C) shouldn't make a difference. The problem most likely lies with the used charger itself or the cable. Do both work correctly on different devices (and not only the one they came with)? Because one or both might be out of spec (like a OnePlus/Oppo Dash/VOOC charger for instance).

There are severe problems with USB-C charging, see: (+) Usb-c charger overheat when I plug my Garmin edge 1040 solar why? - Edge 1040 Series - Cycling - Garmin Forums

Users report that Garmin advises to use only the original USB-A/USB-C cable for charging (so charging with USB-C PD is NOT recommended, would need another cable).

In that case, it seems like Garmin itself isn't adhering to the USB specifications, which should not be expected from a respected and established manufacturer.

That's like saying the new 4-lane highway goes faster than the old 2-lane one. The highway doesn't go faster, the car does. As long as you don't provide more throttle to your car, the 4-lane highway goes at the same speed as the 2-lane one.

The throttle is the Garmin signalling how fast it wants to go. The car is the charger: it responds to your input, but within its limits. It only goes fast if you provide it with full throttle, and if you keep giving full throttle at its max speed, it doesn't accelerate any further.
The highway is the cable and connector: it imposes speed limits, and a wider highway can allow for faster speeds without accidents. However, drive a tractor (charger) on the 4-lane highway or give 10% throttle (Garmin), and you won't go at or near the max allowed speeds.

Connecting the same charger to the same device via a different connector doesn't automatically increase charging speed. If it did, my 5 watt e-reader would be fried within seconds by the 65 watt PD charger I use for everything from wireless earbuds to laptops. However, all these devices adhere to USB specs. They communicate the desired charging voltage and amperage to the charger via the methods defined by USB specs, like all USB compliant devices do.

If the Garmin overheats when charged via a USB compliant charger and cable, the Garmin doesn't adhere to USB specs, which is, in my opinion, dangerous and unforgivable. It's like connecting your 110 watt TV with a 110/220 volt mains connector and having it explode, because the wall outlet has a max output of 3600 watts. The maximum power of the outlet (charger) should be and usually is irrelevant as long as it can provide the output required by the connected device.

If this whole story doesn't make it clear to you why the USB-C connector shouldn't be a problem (as long as all devices adhere to USB specs!), I'm afraid I can't make it any clearer to you.

Finally, nearly all portable electronic devices are slowly but steadily transitioning towards USB-C. Some modern laptops, like MacBooks, don't even provide USB-A connectors any more. If Garmin, after all these years of customers complaining about micro-USB, intentionally released a device that only works on a USB-A connection, that would be a very strange, unnecessary and unwise choice.

This doesn't mean that the advice to use the supplied cable is unusual: nearly all manufacturers give this advice, because they can stand behind the quality and compatibility of things they supply. This prevents liability when someone blows up their device and burns down their house, because they ordered a 200 watt non-compliant 'USB' charger from AliExpress. This doesn't mean the device shouldn't be able to be safely used with other compliant, quality chargers and cables.