So I did a quick test of different USB-C Chargers on my Slate AX:
Interesting - so tried powering it up with:
Scosche vs Stock GL-iNet adapter in photo
You can use any GaN power brick as long as you use a USB-A to USB-C cable. The router does not have true USB-C, its basically out of spec 5V (aka doesn’t have a PD chip, nor the resistors to tell USB-C to output 5V that are required). If your adapter only has USB-C ports, you could use an OTG adapter + the cable to get it to work.
The reason the GL routers are not using true USB-C with PD for example is every time you plug something into another USB-C port, the router would reboot. If this happens while you are changing configuration on the router, files will be corrupt and you would need to unbrick the device.
Also, the router only really needs 2A. The extra 2A are for external harddisks and other things you might connect to USB. Users in the past have had to use powered usb hubs to use external disks, which was a pain.
Thanks - some helpful info there! Weird that the Scosche device works. I really wish GL-iNet had spent a bit more money on a compact power adapter for us given it has an unusual spec.
Might be the Scosche is not fully complaint. The USB-C spec says that no power should be output from the adapter if the resistors are not detected on the other end (connected device) or the USB-C handshake.
So that it works with the router is good, but also bad since it shouldn’t as the others.
Hmm @alzhao can we get GL-iNet to specify what is safe to use and not safe to use as replacement/alternative adapters for the Slate AX? IE are USB-C bricks ok, or should we only use USB-A bricks, what size/output. You mention 3A but @Johnex mentions 2A.
Thanks
Usage with Adguard Home + Wireguard server.
It hovers around 1A, max 1.2A and lowest 0.9A.
2A is enough for just the router.
I think as long as it works, it is safe to use.
TypeC chargers has safe regulations. If they cannot detect PD protocol, they should output nothing or just 5V. 5V is good to go.
Thanks - good to know on different chargers reacting differently. Likely the explanation for why some worked and some don’t.
I think it would be great for GL-iNet to either release a compact travel charger for the AX, or to find one they recommend we can use safely.
For now I think I will try to find the highest output reasonably sized USB-A charger and use a USB-A to C cable
Can you try it with a USB Stick or Hard drive plugged in? Would be neat to see how that impacts the current draw. 2 amps of overhead seems like a lot as far as the stock power brick is concerned.
In my day job my customers keep asking me the same question, over and over again. But it is not possible to answer.
If I sell an electronic device with a suitable power supply, I have to guarantee, it will work in the given specs. If a customer don’t like the PS, he/she/it is free to change it, but it should met the given specs.
If I, as seller, recommend another device, 80% of my customers can be happy. But if the vendor is changing the internals in exact this device, I am responsible for any damages. Only because I recommended it.
It is the same with WLAN cards. I remember the Orinoco gold (802.11b). One batch was excellent for use with Linux 2.2, the next was crap. The same later with the Netgear WG111 (802.11b/g), even if they used v2 and v3 to make it a little easier.
And if you’d think this is quite the past, look up the amazon reviews of the recommended Kali Linux cards…
And in my case, I will prepare my RV with a DC/DC converter. I’m glad I don’t have to pay more for a PS, I won’t use after the testing.
Sorry for the long reply, didn’t have an external disk to test on. Here is a small laptop harddisk running off USB:
Still well under 2A with a small disk.
Thats all well and good but, try saving a 4k video file to the hard-drive then stream it it to a device and see what the drawl is. Plus its a good reason to watch movies on company time. 
On modern drives you can see what the max amp draw will be from the label (at least on branded ones) like this:
Mine is a smaller laptop drive, and i know it does not pull more than 300mA at any load.
The image above i posted is a frame from a video i made while the disk was doing random read, and i took the frame that has highest current draw.
Larger disks can use much more power, so it will depend on your use case. A 3A adapter is more than enough for a full size spinning hdd. 2A is more than enough for a small laptop drive, sdd or usb stick.
Also keep in mind when using a smaller power adapter. The lower rating it has, and the more amps you pull, the hotter and more stressed it will be. If you are using a cheap china brick it might even be overspeced, and you come a gutser.
If you decide to go with a 2A adapter and you are running it at 1.9A constantly, it will be super hot and might die very fast. I like to always add 1A or so headroom when it comes to power conversion (even DC to DC).
If you will be running the router at home, use the included adapter.
If you decide to use another adapter and something happens or you have data loss or something else, it was at your own risk 
Also, there has been a big effort to bring the little externals within the 500ma spec of USB2 so you don’t have to have the Y plug anymore. The bigger capacity 2.5/1.8 drives are usually USB3, so you can’t tell, but if you have a USB2 drive without a Y cable, you should be in good shape.
Ravpower PD Pioneer 65W, works from USB-A ports on the charger while my laptop is hooked on USB-C output
Does it stay on if you plug/unplug other devices from the charger? Or does it reboot if you do that. (ie device being plugged in or out of the RAVPower charger. Thanks!
router didn’t restart upon connecting/disconnecting laptop from the USB-C port
I would suggest Glinet to use USB-PD for future models.
I would love PD. With how much space there is in these mini routers now it shouldn’t be too hard to solder one in place. They’re very tiny.
