RT-BE86U USB ports - how much power do they provide?

[Qbcd]

Hello, I'm wondering if it would be possible to power an ONT and a DSL modem using the USB ports on the back of the RT-BE86U router. They are both 12V devices, so I would be using those 5V to 12V step-up USB to barrel plug cables. Neither device uses more than 5W, so if the ports can provide 1A, it would work. But I can't find the power rating of the ports anywhere.

I know you'll say not to do it, but I'm wondering if anyone has tried it and if has worked, and/or what the actual spec of the USB ports is. I remember years ago reading about someone powering an ONT from an Asus router, but I can't find it now.

 

[Richard1864]

Hello, I'm wondering if it would be possible to power an ONT and a DSL modem using the USB ports on the back of the RT-BE86U router. They are both 12V devices, so I would be using those 5V to 12V step-up USB to barrel plug cables. Neither device uses more than 5W, so if the ports can provide 1A, it would work. But I can't find the power rating of the ports anywhere.

I know you'll say not to do it, but I'm wondering if anyone has tried it and if has worked, and/or what the actual spec of the USB ports is. I remember years ago reading about someone powering an ONT from an Asus router, but I can't find it now.

1. The USB ports on routers aren't designed to power ONT's or modems.

2. The ONT and modems have to be plugged into the wall because they can easily use more than 5 watts under load.

3. If they're powered by the router then you'll never get online; ONT and modem have to already be fully powered BEFORE the router is turned on for the router to get online. That can't happen if they're powered by the router.

The USB ports can't even charge a cell phone, so they don't definitely can't power a modem or ONT. Tried it myself.

 

[Qbcd]

1. The USB ports on routers aren't designed to power ONT's or modems.

2. The ONT and modems have to be plugged into the wall because they can easily use more than 5 watts under load.

3. If they're powered by the router then you'll never get online; ONT and modem have to already be fully powered BEFORE the router is turned on for the router to get online. That can't happen if they're powered by the router.

The USB ports can't even charge a cell phone, so they don't definitely can't power a modem or ONT. Tried it myself.

Actually, this reminded me that my phone charged pretty quickly when I tested dual WAN with it, and then I remembered that I had a USB meter. So I tested the ports and both output 1.5A or about 7.4W! So it should be enough for the modem and ONT. But I couldn't test both simultaneously. I'll just try it and see if it works and report back.

My DSL modem (Draytek Vigor 130) never draws more than 5W, I've tested it under full load. And my ONT is the Adtran SDX621i, which has a max rated power draw of 6W. And no, they don't have to be turned on before the router turns on. Maybe the router you tested had low-power ports, but the BE86U seems to be ok in that department.

 

[degrub]

Try it and report back. Worst that can happen is it overheats and damages the USB controller.

Was that testing both ports simultaneously ?

 

[Qbcd]

Try it and report back. Worst that can happen is it overheats and damages the USB controller.

I thought about this, whether it would be putting a strain on the router's VRM. The router runs on 12V, so it would be stepping down 12V 0.8-1A to 5V constantly. That should generate at most 1W of heat. It probably has a heatsink on the VRM and overheat protection. If the ports are designed to deliver that much power, it should be fine. I've never heard of VRM or USB controller wearing out or breaking because 1.0-1.5A was drawn from USB ports. So overall, I think it's a very low probability of anything breaking. Even if the ports die, it's worth a shot, I'd never use them for anything else.