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Which micro USB cable here actually works?

  • Malvineous Saturday, November 8, 2014 11:09 AM Reply
    Hi all,

    I've bought a handful of different micro USB cables from DX, but they all use wires that are too thin and can't carry enough current, so they charge slowly and don't work at all with devices like the Raspberry Pi.

    There are hundreds of micro USB cables on the site, and it takes a very long time to go through each one and read all the reviews until you find one that finally says "does not work with Raspberry Pi" or "cannot deliver more than 20mA".

    So to speed things up, I thought I'd ask here. Does anyone know whether DX sell a USB to micro USB cable that is capable of delivering at least one amp (preferably two amps) with no voltage drop? The wires in the cable would have to be fairly thick to do this, so it wouldn't be cheap. But I am happy to pay 10 times the normal price for a cable that actually works with high-current devices!

    Any suggestions? Thanks!
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  • sheepish Top 10 Forum Poster Saturday, November 8, 2014 1:27 PM Reply
    with no voltage drop

    DX doesn't sell superconducting cables, sorry.
    Remembering 30 years.
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  • Malvineous Saturday, November 8, 2014 2:04 PM Reply
    Sorry, perhaps I was unclear. Typically in phone charging applications and powering of small electronic devices, superconductivity is rarely required. In these types of applications "no voltage drop" is widely understood short-hand for "minimal voltage drop with the given load, typically in the range of 0.1 volts or less." Since I mentioned my load was 1-2 amps, this would mean a cable with thick enough conductors to deliver 1-2 amps with a voltage drop of only 0.1 volts. Many of the cables here (based on my own experiences and reviews from others) have voltage drops on the order of 0.8 to 2.5 volts, as the load approaches merely one amp. This results in anything from insufficient charging to devices like the Raspberry Pi not even powering up, or giving brownout warnings.

    The problem is that even cables sold as "charging cables" exhibit this problem, with many customers complaining that the cable is not able to charge their phone, despite being sold as such. The matter is made even more difficult by the fact that none of the items list the size of their conductors, except a few which list the size of the cable (and again based on my own experience, this often means extra-thick insulation and still small conductors.)

    All this means it is nearly impossible to find a micro USB cable that works reliably and can deliver the required amount of power. Superconductivity is not required, but the alternatives I have found here so far seem much closer to no-conductivity instead.
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  • sheepish Top 10 Forum Poster Saturday, November 8, 2014 2:16 PM Reply
    The trouble with finding something like that on DX is that a typical generic cable here is made from the thinnest and cheapest wire that will still conduct after being bent a few times. It could be argued that China has not yet figured out that there is a market for quality, but it could also be argued that they know very well where the main market is. Anyway, good quality cables are sold elsewhere, and of course at a price to match.
    Remembering 30 years.
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  • MJdub Saturday, November 8, 2014 3:30 PM Reply
    I have not really done any testing on generic cables; I buy all my USB cables from a certain site that brands their own cables etc. They have good quality and low prices so I've never really shopped around for USB cables. Their USB cables use 24 AWG wire for power and 28 AWG wire for data.
    I tried searching DX for "Micro USB AWG," in an attempt to find micro USB cables that specify their wire gauge. Whether or not they are telling the truth is another story, but it's a start. Actually it looks like all but one is USB 3.0 so the only real result is sku.270111. The specs say "2824awg" which leads us to believe that the power conductors are 24 AWG which should be enough to carry a couple of amps. I've had no trouble with a Raspberry Pi on 6 ft of 24 AWG cable. Ten feet of 24 AWG wire should theoretically have ~0.25 ohms of resistance and cause less of a voltage drop than you've experienced with other cables.
    Disclaimer of course is that I have not bought the cable I linked to and I don't know if the specs are accurate. However as sheepish mentioned you are probably better off buying from somewhere with more reliable and consistent product specs when power handling is a concern as this is rarely/never a concern in the design of cheap cables.
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