Joined Nov 2007
L4: Apprentice
Forum Thread
Do you need a special USB cable for 2 amp charging?
September 11, 2013 at
07:05 AM
I have a question about the USB cables. Are all micro USB cables capable of carrying 2.1 amp at .5v or do you need one spec'd for that? My guess is that the wall charger, or cigarette lighter adapter is what dictates how much juice is supplied and how fast, but I just wanted to know if the USB cable can also be a limiting factor. Also, is there a difference between charging off the computer using a USB 3.0 port vs standard USB port?
I've got a bunch of AC/USB wall plugs (mini-bricks? not sure what they're called) from my old palm pre phones as well as from nooks and galaxy note 2, and was wondering if I can use any old cables with them and get the faster charging or if I have to be careful not to get the good cables mixed up with cheap ones from other devices?
Thanks
I've got a bunch of AC/USB wall plugs (mini-bricks? not sure what they're called) from my old palm pre phones as well as from nooks and galaxy note 2, and was wondering if I can use any old cables with them and get the faster charging or if I have to be careful not to get the good cables mixed up with cheap ones from other devices?
Thanks
About the OP
17 Comments
Your comment cannot be blank.
Sign up for a Slickdeals account to remove this ad.
The official power specifications for USB are as follows:
USB 2 - 500mA
USB 3.0 - 900mA
However, many implementations offer more power than that.
The official power specifications for USB are as follows:
USB 2 - 500mA
USB 3.0 - 900mA
However, many implementations offer more power than that.
OP, this app [google.com] may be able to help you out, if you have an android device which will report current information.
A Monoprice USB cable [monoprice.com]has 28 awg conductors in it. 28 awg is rated for 1.4/0.22 A (VAC) according to here [powerstream.com]. Those numbers are for chassis wiring and power supply (respectively).
I am not an electrical engineer, so the AC/DC question (does it matter if 120VAC or 5VDC?) I googled and apparently current is current [allaboutcircuits.com].
If we use the higher of the two numbers above, the minimum AWG acceptable for 2.1A is about 26 AWG (2.2/0.361). I'd have to believe we look at the left number as we don't get to 2.1 on the right number until 18 AWG and for USB that'd be one huge ass cable!
Looking at a USB 3.0 cable [monoprice.com], it's listed as 28/24 AWG - which is likely a difference between the number of required conductors in 3.0 (9 vs 5?).
At any rate, you can buy a heavier gauge USB2 wire (I couldn't find info on AWG in MP's "premium" cables), butthese are the ones [amazon.com] I use for all my devices.
Sign up for a Slickdeals account to remove this ad.
can someone show me a usb cable, that i can use for 2.1amp?
ebay link/amazon appreciated. (even if its from china thats ok).
-Current is current regardless of if it's AC or DC.
-Most reasonably high quality usb cables work fine at 2.1A
-If the cable specifies wire gauge, a smaller AWG number equates to a larger cable and larger current carrying capacity.
-consulting "electrician" tables isn't going to be particularly helpful or relevant. They generally don't go low enough in current to be relevant, are based on much longer runs of wire, and are fairly conservative.
-the shorter a cable of give wire gauge is, the more current it can carry.
-Don't expect wonders from a cable that costs $0.99
-If the cable feels warm, when charging you should replace it / replace it with a better cable. Cables that have developed breaks in some of the wires are more likely to get warm as a result of reduced current capacity. A poorly constructed or undersized cable could also get warm
-Newer rapid chargers use low voltage AC instead of lower voltage DC (5V) which allows similarly sized cables and connectors to carry more power. Eg. 5VDC*2A = 10W, 30VAC*1A = 30W
-Current is current regardless of if it's AC or DC.
-Most reasonably high quality usb cables work fine at 2.1A
-If the cable specifies wire gauge, a smaller AWG number equates to a larger cable and larger current carrying capacity.
-consulting "electrician" tables isn't going to be particularly helpful or relevant. They generally don't go low enough in current to be relevant, are based on much longer runs of wire, and are fairly conservative.
-the shorter a cable of give wire gauge is, the more current it can carry.
-Don't expect wonders from a cable that costs $0.99
-If the cable feels warm, when charging you should replace it / replace it with a better cable. Cables that have developed breaks in some of the wires are more likely to get warm as a result of reduced current capacity. A poorly constructed or undersized cable could also get warm
-Newer rapid chargers use low voltage AC instead of lower voltage DC (5V) which allows similarly sized cables and connectors to carry more power. Eg. 5VDC*2A = 10W, 30VAC*1A = 30W
I see I replied earlier but anecdotally, all my android stuff charges at 2.1A; I never pay attention to the cables used (meaning I don't only use certain cables for this); I've never had a problem with any of the cables and I've never had any of them even become warm. This includes the OEM cables (Samsung), the higher-rated Amazon cables (see my link, but I've bought 3-4 different ones) and the cheapo ones that come with some Chinese devices.
I really think this is getting way too analytical.
The usb-c / usb power delivery spec can deliver up to 100W of power. For this type of application you certainly want to be careful when selecting chargers and cables.
-Current is current regardless of if it's AC or DC.
-Most reasonably high quality usb cables work fine at 2.1A
-If the cable specifies wire gauge, a smaller AWG number equates to a larger cable and larger current carrying capacity.
-consulting "electrician" tables isn't going to be particularly helpful or relevant. They generally don't go low enough in current to be relevant, are based on much longer runs of wire, and are fairly conservative.
-the shorter a cable of give wire gauge is, the more current it can carry.
-Don't expect wonders from a cable that costs $0.99
-If the cable feels warm, when charging you should replace it / replace it with a better cable. Cables that have developed breaks in some of the wires are more likely to get warm as a result of reduced current capacity. A poorly constructed or undersized cable could also get warm
-Newer rapid chargers use low voltage AC instead of lower voltage DC (5V) which allows similarly sized cables and connectors to carry more power. Eg. 5VDC*2A = 10W, 30VAC*1A = 30W
They do sell 24/28 AWG micro USB cables, monoprice has some. http://www.monoprice.c
In this case the power wire is 24AWG and the data wire is 28AWG. I would not trust a cheap no brand china cable to have 24AWG power wires.
I really think this is getting way too analytical.
Gauge of the cable does matter. The 28/24 gauge cables are what you want. Especially if it's longer. The really cheap cables usually use a thinner gauge and are not able to carry as much current. Now this all kind of changes with the Qualcom quickcharge stuff. thinner gauge cables are ok, but your still best with a 28/24.