Buying 2A micro USB charging cables - Page 1
Forum section: electronics / projects

author: splin
author_rank: Frequent Contributor
timestamp: September 27, 2015, 05:49:19 pm
content: I want to buy some micro USB charging cables that will fast charge ASUS Memopad and HUDL tablets, Moto G and Nokia Lumia phones. But how can you identify which cables will charge at 2A or more as I understand that there are various different ways of signalling to the device that a high power charger is connected including resistors biasing the data lines.Is this done in the charger or the cables? Are there universal cables/chargers or are some device specific?

author: Monkeh
author_rank: Super Contributor
timestamp: September 27, 2015, 05:54:17 pm
content: It's done at the charger, not the cable.Decent cables are easily found:http://www.amazon.co.uk/dp/B00QT2BLC4http://www.amazon.co.uk/dp/B00WMCIH90http://www.amazon.co.uk/dp/B00YAF14QK

author: splin
author_rank: Frequent Contributor
timestamp: September 27, 2015, 06:22:36 pm
content: Quote from: Monkeh on September 27, 2015, 05:54:17 pmThanks, I'll buy one of those. But I have some cables which will only charge at .5A when connected to the same charger. They work as data cables so it's not because the data lines aren't connected and I doubt its due to the voltage drop in small gauge wire. So what might be going on? I also have one thin but short (approx 300mm) cable which came with a cheap bluetooth keyboard, which won't charge some devices at all but will others - but only at a low rate.

author: mikerj
author_rank: Super Contributor
timestamp: September 27, 2015, 06:48:07 pm
content: Quote from: splin on September 27, 2015, 06:22:36 pmIt probably IS the voltage drop. A lot of phones/tablets have pretty intelligent charging system and will back off the charging current if they see excessive voltage drop (which could be due to a charger of inadequate current rating, or a cable with high resistance.

author: splin
author_rank: Frequent Contributor
timestamp: September 27, 2015, 06:55:49 pm
content: Hmm. This one:http://www.amazon.co.uk/dp/B00MN2B2MI?psc=1Says: "Ultra-compatible: The D+ and D- data pins in the micro USB plug are already shorted, making the cables compatible with 90% of devices with a micro USB port, including phones, tablets, external batteries, and more."Which suggest some 2A chargers leave it to the cable to provide the signalling. And also suggests there are some devices which are different and require specific cables or chargers. Silly me thinking the EU had mandated micro USB charging for mobiles to ensure compatibility.

author: Monkeh
author_rank: Super Contributor
timestamp: September 27, 2015, 06:59:42 pm
content: Quote from: splin on September 27, 2015, 06:55:49 pmNo, those are to fool devices into working with chargers they don't support. And then you have a bunch of cables which mysteriously won't work as data cables. Stupid idea.Some cables do not have a shield, or use the shield for the ground pin. Devices may well use that as a signal to avoid charging at a high rate.

author: HKJ
author_rank: Super Contributor
timestamp: September 27, 2015, 07:45:04 pm
content: Quote from: splin on September 27, 2015, 05:49:19 pmUsual it is done in the charger, but there are a few cables that implements coding and you can also get some adapters with coding.You have to watch out for "charge only" cables, they are missing the data connections that are used for the coding.You can find universal chargers, you can see test of many chargers here:http://lygte-info.dk/info/ChargerIndex%20UK.html

author: Kilrah
author_rank: Unknown
timestamp: September 27, 2015, 07:57:00 pm
content: The charger uses the shorting to signal its ability to supply more current, so having that in the cable is actually mistreating the charger if it can't. I wouldn't use one of those as what actually happen will depend on the charger/device combination and can't really be predicted.And yes some cables have ridiculously thin and lossy wiring, and it's impossible to know how good/bad they are without testing. I've had a nice, thick cable with ferrite beads that looked as "serious" as possible but that was only good for the trash when a 4mm thin and flimsy looking cable works perfectly well.