USB Cables: Charge-only?

[epiphani]

I realize part of the reason LTT is interested in doing USB cables is the quality of data connections, but I'd love a high-quality, high-power charge-only cable that I could feel confident using in public places.  Is it possible and/or in the list of options that will be coming with the USB cables?  My biggest concern by far using public charging options (planes, hotels, etc) is the fact that I effectively have to trust that the plug is safe.

 

Edit:  I've seen comments elsewhere that mention that data is required by the USB spec, but given how much USB-C is taking over the low-voltage power space, I'd really like to have cables that can be clearly trusted to only do power delivery.

[Timme]

Get a power bank, like this one, and a brick for when you have an outlet. Then you'll never have to worry about charging.

[Blue4130]

13 minutes ago, epiphani said:

I realize part of the reason LTT is interested in doing USB cables is the quality of data connections, but I'd love a high-quality, high-power charge-only cable that I could feel confident using in public places.  Is it possible and/or in the list of options that will be coming with the USB cables?  My biggest concern by far using public charging options (planes, hotels, etc) is the fact that I effectively have to trust that the plug is safe.

 

Edit:  I've seen comments elsewhere that mention that data is required by the USB spec, but given how much USB-C is taking over the low-voltage power space, I'd really like to have cables that can be clearly trusted to only do power delivery.

You need the data for the PD handshake. Without it, best you will do is slow charging. 

 

Plus, I can't think of any place that has fast charging ports unless you plug in your own brick. 

[epiphani]

25 minutes ago, Blue4130 said:

You need the data for the PD handshake. Without it, best you will do is slow charging. 

 

Plus, I can't think of any place that has fast charging ports unless you plug in your own brick. 

I can think of interesting ways one might be able to solve the handshake problem... (ie, inline chip to handle the handshake from both sides).  Yeah, I realize this is probably outside of the scope of what LTT could do.

 

And re fast charging in public - I've seen it in hotels.  It's going to be more common as USB-C becomes the default for charging any low voltage device.  USB-C ports will likely become more globally accepted than any other power plug.

[OhioYJ]

29 minutes ago, epiphani said:

inline chip to handle the handshake from both sides

This seems like a great way to fry something.  Imagine someone grabbing a laptop cord, or it gets designed wrong: 

 

Chip 1 - Send 240 watts.

Chip 2 - Send 240 watts.

End User: Why is the power brick and my phone getting so hot and smokey? 

 

Honestly I'd still prefer to slow charge my device anyways, it's better for the batteries*.  (*still my opinion and I'm sticking to it)

[Poinkachu]

55 minutes ago, epiphani said:

And re fast charging in public - I've seen it in hotels.  It's going to be more common as USB-C becomes the default for charging any low voltage device.  USB-C ports will likely become more globally accepted than any other power plug

I wouldn't even trust a partially obscure brand of a PD/QC power brick for sensitive/expensive devices, especially if it's a shit ton of watts.

[saintlouisbagels]

7 hours ago, Timme said:

Get a power bank, like this one, and a brick for when you have an outlet. Then you'll never have to worry about charging.

Going to have to agree with this answer.

Why go through the hassle of finding a fancy power-only USB cable when you can just charge literally anywhere you go with a good power bank.

 

I cannot imagine a situation where I'm out in public with a USB cable and NOT a charger/power bank.

And especially in what public setting would I be in where there are only USB ports available and no outlets??

[Blue4130]

43 minutes ago, saintlouisbagels said:

Going to have to agree with this answer.

Why go through the hassle of finding a fancy power-only USB cable when you can just charge literally anywhere you go with a good power bank.

 

I cannot imagine a situation where I'm out in public with a USB cable and NOT a charger/power bank.

And especially in what public setting would I be in where there are only USB ports available and no outlets??

Not a public place, but airplanes. In most of asia, powerbanks are not allowed anymore an in flight outlets are few and far between.

[saintlouisbagels]

9 hours ago, Blue4130 said:

Not a public place, but airplanes. In most of asia, powerbanks are not allowed anymore an in flight outlets are few and far between.

Ah, thanks for the info.

I've traveled to Vietnam 5x times in the past few years using Singapore, Korean, and Japan airlines and none of them mentioned anything about a power bank ban.

[Blue4130]

16 minutes ago, saintlouisbagels said:

Ah, thanks for the info.

I've traveled to Vietnam 5x times in the past few years using Singapore, Korean, and Japan airlines and none of them mentioned anything about a power bank ban.

It's new as of about 4 months ago. The list of airlines keeps growing.

 

[LogicalDrm]

1 hour ago, Blue4130 said:

It's new as of about 4 months ago. The list of airlines keeps growing.

 

I'm pretty sure that limits (100Wh / 20k mAh) has been in place in European airlines for longer. At least couple of years since I remember checking on regulations when shopping for my summer 2023 Europe trip. Its not massive thing either. For example M4 Macbook has 72Wh battery. So you can have fully charged laptop and enough battery to fully recharge it. 

 

Reading on national airline, Finnair, regulations. Limit in terms of numbers is 15 devices and 20 powerbanks that are under that 100Wh limit. Or with special approval, max 2 devices that go over that limit. 

 

***

 

I don't think this will happen. You are essentially asking for features you can achieve already just by bringing your own charger. And protection against using data connection without your permission is done anytime you connect new USB device to power source where more than power is detected.

[Blue4130]

33 minutes ago, LogicalDrm said:

I'm pretty sure that limits (100Wh / 20k mAh) has been in place in European airlines for longer. At least couple of years since I remember checking on regulations when shopping for my summer 2023 Europe trip. Its not massive thing either. For example M4 Macbook has 72Wh battery. So you can have fully charged laptop and enough battery to fully recharge it. 

 

 

 

The new ban isn't a size issue. That was in place for years. This is a complete ban on using battery banks on planes. You can have fully charged banks, but you *can't* use them on many airlines.

[LogicalDrm]

58 minutes ago, Blue4130 said:

The new ban isn't a size issue. That was in place for years. This is a complete ban on using battery banks on planes. You can have fully charged banks, but you *can't* use them on many airlines.

Thanks for clarification. I didn't read up properly. From another look, national airline allows use on flight, not during takeoff or landing. Norwegian, one of the biggest "cheap" airlines doesn't allow use at all.

 

It will be interesting to see whether aircraft manufacturers, mainly Airbus, will adjust to this. While new trend has been to allow USB-A/C ports on planes, the previous generation had proper power outlets between seats. I remember charging my laptop when flying from Japan back to Europe in 2013.

[OhYou_]

On 8/4/2025 at 3:55 AM, OhioYJ said:

This seems like a great way to fry something.  Imagine someone grabbing a laptop cord, or it gets designed wrong: 

 

Chip 1 - Send 240 watts.

Chip 2 - Send 240 watts.

End User: Why is the power brick and my phone getting so hot and smokey? 

 

Honestly I'd still prefer to slow charge my device anyways, it's better for the batteries*.  (*still my opinion and I'm sticking to it)

that's not how any of this works
the cable doesnt just consume power at 240w, the phone will still only pull as much as it wants. 

forcing the cable to decide the voltage (wattage) for you will just result in you plugging in the cable, the cable requests 240w mode, the charger switches to 48v 5A mode,  you plug in the phone, it dies. 

the most you can do with a no data cable setup is request 5v 3A 15w mode, then the phone if it can do 15w on 5v, it will, if it cant, it wont, it will self regulate. 

[tkitch]

devices like these exist:
https://securitybase.com.au/products/usb-c-data-blocker

 

you can use any usb C cable, and stay safe

[helgehelge123]

Please don't attack me, I'm already carrying my own powerbank.
But is there a real risk of something happening? My iPhone is doing nothing without me confirming the "Trust this device" button.

[OhioYJ]

6 hours ago, OhYou_ said:

that's not how any of this works
the cable doesnt just consume power at 240w, the phone will still only pull as much as it wants. 

I know it's not how it works, I was just pointing out you can't have a dumb chip on each side. PD will require data transfer. You can have both sides just blindly saying feed 15V without knowing if the otherside supports it. 

 

If the two chips can communicate, then the cable might as well be a regular USB cable, as it can clearly transfer data, and is once again a security concern. 

[LogicalDrm]

12 hours ago, helgehelge123 said:

Please don't attack me, I'm already carrying my own powerbank.
But is there a real risk of something happening? My iPhone is doing nothing without me confirming the "Trust this device" button.

There's some risk always. Just like there's always risk when you use credit card. Which is why I personally don't support using just phones own security as guardian to my whole life. 

[OhYou_]

17 hours ago, OhioYJ said:

I know it's not how it works, I was just pointing out you can't have a dumb chip on each side. PD will require data transfer. You can have both sides just blindly saying feed 15V without knowing if the otherside supports it. 

 

If the two chips can communicate, then the cable might as well be a regular USB cable, as it can clearly transfer data, and is once again a security concern. 

ic. 
i disagree tho if the cable itself only talks to the phone for PD data and then relays that to the charger, and nothing else. then that is reasonable security so long as the cable is from a reputable brand/source. 
huh this is actually a decently marketable idea I think, either a cable or a usb "condom". 

like you're not going to like pop a 0day on a tiny microcontroller that is literally just doing pd negotiations, there is no way for the charger to break through that unless its implemented with a very costly solution on purpose to be insecure. 

I actually have something like this i could use, it is a usbc to thinkpad slim tip 20v adaptor and then i have the literal opposite to go back to usb-c. 
since there is only raw 20v going between the two, there is no chance of a data leak. 
the one end simply tells the charger to give it 20v always, and then the other end is a standalone charger itself designed to take in that 20v and give the device whatever. 

[apoyusiken]

On 8/4/2025 at 1:55 PM, OhioYJ said:

Honestly I'd still prefer to slow charge my device anyways, it's better for the batteries*.  (*still my opinion and I'm sticking to it)

youre right and thats my opinion too, (I dont fast charge unless i need to) however some recent tests show that fast charging is better for batteries (mostly about the margin of error of the tests and more cycles when you charge faster). Obviously doesn't mean fast charging is better but at this point if you are reluctant to do it because of your batteries, it is probably safe to use and you don't need to worry. However I also don't like that it heats up the devices.

[OhioYJ]

5 hours ago, OhYou_ said:

like you're not going to like pop a 0day on a tiny microcontroller that is literally just doing pd negotiations, there is no way for the charger to break through that unless its implemented with a very costly solution on purpose to be insecure. 

While I agree it could be a great idea, it's still a security risk. As soon as you say it's secure, some security researcher (or worse) will take it as a challenge to find some way to exploit it.