Maximum current in USB 2.0 and USB 3.2G1 cables

Thread Starter

MalcolmPM

Joined Jul 22, 2022
1
Hello,

I am looking for a USB A-C and C-C cable with a length of 5 meters to charge my device. I found a USB cable with AWG26/22 standard and unfortunately the voltage drop for USB 2.0 is significant, i.e. for 4.75V lower limit the maximum load is only 1A, although the manufacturer declares 5A and 100W and compatibility with PowerDelivery.

Do I understand correctly that in the PD standard, the power is supplied via dedicated USB 3.2Gen1 lines i.e. 4xAWG26 where the total cross-section will be the equivalent of AWG14 and the permissible current of 5.9A?
I wonder how it is possible that such thin USB-C cables can transfer as much as 100W of power.

Link to a sample product:
https://www.alibaba.com/product-det...?spm=a2700.shop_plser.41413.12.671f2021DAMReM

I will be grateful if any of you share your opinion on this matter.

Malcolm
 

MrAl

Joined Jun 17, 2014
9,633
Hi,

The way i understand it is that the cable manufacturer makes the cable to fit a particular power level. If they lie about it, they lie about it, but if they also give the wire size then you know they lied about it if things dont add up.
Check some other cables and compare wires sizes and ratings.

4 wires of AWG 26 will not be the same as AWG 14 no way. 40 Ohms per 1000 feet vs 2.5 Ohms per 1000 feet, so 4 AWG 26 wires will present 10 Ohms per 1000 feet which is still not close really. Try 16 wires of AWG 26 to equal a single AWG 14 wire.
Now 4 wires of AWG 20 will be about equal to a single AWG 14 wire.

The max current for a USB 2.0 port is 500ma i think.

Partial wire table...
Code:
 12     6528.6      1.588      0.0808    2.0523     10.9        5.208
 13     5184.0      2.003      0.0720    1.8288      8.6        6.569
 14     4108.8      2.525      0.0641    1.6281      6.8        8.282
 15     3260.4      3.184      0.0571    1.4503      5.43       10.44
 16     2580.6      4.016      0.0508    1.2903      4.30       13.17
 17     2052.1      5.064      0.0453    1.1506      3.42       16.60
 18     1624.1      6.385      0.0403    1.0236      2.71       20.94
 19     1288.8      8.051      0.0359    0.9119      2.15       26.40

 AWG   cmils    Ohms/1000ft   DiaInches  DiaMM   I(600cm/A)    Ohms/KM
 20     1024.0     10.150      0.0320    0.8128      1.71       33.29
 21      812.3     12.800      0.0285    0.7239      1.35       41.98
 22      645.2     16.140      0.0254    0.6452      1.08       52.93
 23      510.8     20.360      0.0226    0.5740      0.85       66.78
 24      404.0     25.670      0.0201    0.5105      0.67       84.19
 25      320.4     32.370      0.0179    0.4547      0.53       106.1
 26      252.8     40.810      0.0159    0.4039      0.42       133.8
 

MisterBill2

Joined Jan 23, 2018
13,808
Consider that the USB arrangement was never intended for use as a power connection, the number 26 conductors will have quite a bit of voltage drop, which is totally reasonable for a high speed data link. To have a high power charging cable you could buy the connectors and build it yourself.
No matter how much people want a #24 wire to carry 5 amps with no voltage drop, it will not happen. Even 2 amps is a stretch.
 

MrAl

Joined Jun 17, 2014
9,633
Consider that the USB arrangement was never intended for use as a power connection, the number 26 conductors will have quite a bit of voltage drop, which is totally reasonable for a high speed data link. To have a high power charging cable you could buy the connectors and build it yourself.
No matter how much people want a #24 wire to carry 5 amps with no voltage drop, it will not happen. Even 2 amps is a stretch.
Hi,

Well consider the length too. A 10 foot cable may be a problem in some areas but a 3 foot cable or even a 1 foot cable may not. For 3 feet of #24 AWG the resistance is about 0.150 Ohms for a two conductor run. At 2 amps that's about 0.300 volts not that great but maybe still works.
However, there is another side to this. With normal charging voltage of 5 volts that limits the power transfer to about 10 watts, but with QC3.0 it's only limited to about 24 watts. Many cell phones are limited to about 15 watts.
So some cables may work in short runs, but i do believe the better cables use heavier wire too.

I know this isnt the point but i found that charging at lower currents is actually much better for the battery. Samsung has a setting (maybe only Android 12 not sure but maybe UI4.0 not sure) that limits charging current and also can limit the top end voltage to 85 percent charged. Those ideas help to promote longer battery life. Not the main point i know but worth mentioning.
 

MisterBill2

Joined Jan 23, 2018
13,808
Consider also how believable many of those claims actually are. That is always true.
And certainly the faster the charge the greater the stress on the battery, no matter what the type is.
 

MrAl

Joined Jun 17, 2014
9,633
Consider also how believable many of those claims actually are. That is always true.
And certainly the faster the charge the greater the stress on the battery, no matter what the type is.
Hi again,

Sorry but i dont quite understand your point. Are you saying that all cable ads are somewhat made up?
 

Ya’akov

Joined Jan 27, 2019
6,857
Hello,

I am looking for a USB A-C and C-C cable with a length of 5 meters to charge my device. I found a USB cable with AWG26/22 standard and unfortunately the voltage drop for USB 2.0 is significant, i.e. for 4.75V lower limit the maximum load is only 1A, although the manufacturer declares 5A and 100W and compatibility with PowerDelivery.

Do I understand correctly that in the PD standard, the power is supplied via dedicated USB 3.2Gen1 lines i.e. 4xAWG26 where the total cross-section will be the equivalent of AWG14 and the permissible current of 5.9A?
I wonder how it is possible that such thin USB-C cables can transfer as much as 100W of power.

Link to a sample product:
https://www.alibaba.com/product-det...?spm=a2700.shop_plser.41413.12.671f2021DAMReM

I will be grateful if any of you share your opinion on this matter.

Malcolm
The PD standard requires a cable length of ≤1m (CC3G2 cable type) to use 5A. Beyond that, you would have to talk to the manufacturer about their choices. The C connector is rated at 5A and of the various standard cable types CC3G2 is the longest—still nowhere near 5m.

Why do you need such a long cable? Can’t you locate the power supply closer?
 

MisterBill2

Joined Jan 23, 2018
13,808
My claim is that much of the advertising writing is done by those with at best no technical background, and at worst a mastery of fiction. So any portion that may be accurate, beyond the price, is incidental.
Also, "Y" makes a good point about the intended maximum cable length. 5 M (15 feet+) is far above the standard.
 

MrAl

Joined Jun 17, 2014
9,633
The PD standard requires a cable length of ≤1m (CC3G2 cable type) to use 5A. Beyond that, you would have to talk to the manufacturer about their choices. The C connector is rated at 5A and of the various standard cable types CC3G2 is the longest—still nowhere near 5m.

Why do you need such a long cable? Can’t you locate the power supply closer?
Hi,

Yeah that is pretty long for a charging cable. Max i have needed in the past was 6 feet and could probably get away with 4 feet if they made them.
 
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