I had P1 Turbo with 5000mah battery. It's SC-13 could 0-100 in under a hour even with wifi enabled.

The charger is broken but I keep the cable. I use a third party 2.1A charger with dual ports. The weird thing is. My G7102 and Note 3 N9000 gets charged slowly with that cable compared to the original cable of Ace 2. Ampere says Samsung cable gives more than 2 times amperage.

Why is that? I don't know electronics can someone explain it to me why is that?

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    i can confirm this behaviour. i have noticed that Samsung phones charges only with Samsung cables, but i don't know the reason. and i am talking about "normal" microUSB <-> USB type A data cable (not the charger) maybe there is a tiny difference in length of contacts? on the other hand the samsung cables works fine for other devices
    – alecxs
    Commented Jul 23, 2019 at 22:37
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    @Turkeyphant i believe this is more related to USB Charging Protocol than resistivity laws. the resistance does control the charging mode electronics.stackexchange.com/questions/177788 but this doesn't explain why Samsung isn't charging at all with non-samsung cables
    – alecxs
    Commented Jul 24, 2019 at 0:08
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    @alecxs the only difference I saw was the three pin design. 2 Power pins and a third pin probably for quick charge communication. So I believe its an internals thing. Commented Jul 24, 2019 at 8:17

1 Answer 1

  1. Because some cables do not meet USB spec and are unable to negotiate faster charging protocols. Faster charging protocols such as USB-PD allow higher voltages and currents which provide a greater charging power to the device and increase charging speeds.

  2. In addition, all cables have a resistance. This is affected by the length and cross sectional area supplying the power pins.

The formula is:

R = ρ L / A

(Where R is resistance, ρ is resistivity, L is length and A is cross sectional area).

Other factors are the plug itself and the amount of power it can draw. Also, factors like QC 3.0 compatibility allow the phone to pull more current at a higher voltage. Phones intelligently decide how much power to draw as well based upon their own tables, the temperature and charge and other properties of the battery.

But, in general, a cable with higher resistance or unable to pull as much power will charge more slowly. Just because a cable is rated for 2A doesn't mean it will achieve this.

To see more detail, I suggest you get a meter that will allow you to measure the precise current and voltage using the same USB plug and different cables.

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