Why are some USB cables better than others at charging?
June 27, 2016 11:53 AM   Subscribe

Exactly as it says above - can someone explain what makes some USB cables better than others?

I'm confused as to why some USB cables perform better than others. They're all electronically identical, right? But just now I unplugged one generic cable (albeit a multiplug one) with another generic (single) cable and the charge time on my phone changed from 4h54m to 1h20m. I also regularly find that my devices (android phone, tablet) aren't recognised when plugged in to a PC with certain cables; although they will charge, there's no data connection. So what should I look for to ensure fast charging and data connectivity?
posted by srednivashtar to Computers & Internet (11 answers total) 13 users marked this as a favorite
 
Some generic cables are just real garbagey. I have one that is weirdly temperamental, in particular.

Also, could USB 2.0 vs. 3.0 be a factor here? There are DEFINITELY speed differences with different types of USB cables. In my experience this is more about data transmission speeds, but could it maybe affect charging as well?
posted by Sara C. at 11:57 AM on June 27, 2016


They're all electronically identical, right?

No. You can tell they're not by the fact that some perform better than others.

It used to be that charging and data cables were separate things. The data pins were shorted on the phone end so that it could detect that the cable was a charging cable, and thus draw more power. But you wouldn't get data. Sometimes the data pins would (also/instead) be shorted in the charger, so that the phone could detect whether it was connected to a charger or to a computer and draw power accordingly when using a true data cable.

But. There's this new thing called QuickCharge that Qualcomm introduced. Most newer Android devices based on current Qualcomm SOCs support it. It requires that the phone actually talk to the charger as a USB device, and tell it how much juice to send. So the cable needs to be the same as any data cable for best charging. So, the ones you have that don't give you data when hooked up to a computer are obsolete in today's QC world.

On top of that, there's now USB-C ("the USB connector that it doesn't matter which way you plug in") and there was a big deal about a lot of these being made wrong such that they could cause a fire, to the extent that Amazon pulled all USB-C cables until they could be verified safe.
posted by kindall at 12:06 PM on June 27, 2016 [6 favorites]


You might want to look into what Benson Leung has been up to for the last bit.
posted by RolandOfEld at 12:12 PM on June 27, 2016 [2 favorites]


It has to do with the gauge of the internal wires. Cheaper cables, have thinner wires (less material), and therefore the cables have a higher impedance.

Devices that have some kind of "smart charging" capability can detect the impedance on the cable, and if it is too high, will charge more slowly for various reasons.

Length is also a factor in impedance, so cheap short cables will work, but cheap long cables (from the same source, so all things remain equal except length) might not. (ask me how I found out and went on the journey that taught me these things).

So what should I look for to ensure fast charging and data connectivity?

Stay under 3ft, or look for a cable that advertises as being 24g (as opposed to 28g), or buy an Anker like The Wirecutter says.

Lifehacker explainer.
posted by sparklemotion at 12:12 PM on June 27, 2016 [7 favorites]


I find that the Amazon basic cables aren't too bad.
posted by k8t at 12:23 PM on June 27, 2016


Also, could USB 2.0 vs. 3.0 be a factor here?

Yes. USB 2 is usually limited to half an ampere. USB 3 usually permits 1.5 ampere. (but you don't get 1.5 amps if you plug a USB3 cable into a USB host port)
posted by Chocolate Pickle at 12:41 PM on June 27, 2016


That should be "USB 2 host port". Sorry.
posted by Chocolate Pickle at 1:07 PM on June 27, 2016


Yes. USB 2 is usually limited to half an ampere.

Technically true, but many many many USB2.0 phones have out-of-standard ways to ask for more juice. My phone charges at just under 1A with the right charger, and it's USB2.0.
posted by BungaDunga at 1:44 PM on June 27, 2016


Yeah, the cheaper cables just don't have the "high-speed charging" capability so they're restricted to 500 mA (which isn't much for charging).

I'm not sure if using a USB3 cable would actually work for high-speed charging if the device itself doesn't support USB3. It might fallback to standard slow-charging USB2.

For cheap but good cables, I always go for Monoprice (especially their iPhone cables). Amazon Basics and Anker are decent too, in my experience. Like lots of electronics stuff, it's mainly a matter of avoiding the bottom of the barrel.
posted by neckro23 at 3:00 PM on June 27, 2016


For cheap but good cables, I always go for Monoprice (especially their iPhone cables).

Monoprice's 10ft 28/28 AWG cables are what sent me down the line of doing research about why some cables worked and some didn't.

The 6ft 28/24 replacements have worked better for me though.
posted by sparklemotion at 3:57 PM on June 27, 2016


Thanks all - some very helpful information here and I feel considerably more informed.
posted by srednivashtar at 1:32 AM on June 28, 2016 [1 favorite]


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