I recently bought a 3m (meter) Apple charging cable and found that it was charging my iPad slower than usual.

I plugged it to a USB tester and found that it charged at ~5v 1A. By comparison, my 1m cable charged at around 5v 2A.

Is it this normal, should there be that much of a difference?

I'm testing by charging an iPad. The wall adapter is the genuine 12W iPad wall outlet rated at 5.2v at 2.4A. I have a genuine Apple 1m cable and I also bought a 3m and 1m cable third party cable off eBay. They are unbranded.

  • Both genuine and non-genuine 1m cables charged my iPad at around 5v 2A.
  • The non-genuine third party 3m, cable charged the same iPad at a bit less than 5v 1A.

The cable nor USB tester gets warms up enough to feel, but the wall plug does, so I don't think it will be (hope it won't be) a fire hazard.

Here are some pictures of the USB tester, maybe that will help. First one is a with the 3m cable

3m charging cable

This one for the 1m cable 1m charging cable

  • There's a lot missing here. Are these charging cables USB-C or something else? Are they genuine Apple or 3rd party? If the latter, what's the make/model (a link would be helpful)? What do you have plugged into the USB tester? Is it the same device or the tester by itself? Make/model of the tester?
    – Allan
    Mar 22, 2019 at 1:28
  • 1
    Also, for wire (assuming 18/20 AWG) the resistance drop is about 42Ω per Km. It can't drop that much from 1m to 3m
    – Allan
    Mar 22, 2019 at 1:31
  • Wouldn’t the tester be more suspect than an Apple cable or might you have gotten a counterfeit cable? Not sure what sort of answer you’re looking for without putting a little more specifics on how you are testing or measuring things. High current charging involved signaling and not just a full on pipe of energy.
    – bmike
    Mar 22, 2019 at 2:04
  • The 3m is a third party cable unbranded, I don't think the tester is culprit as the reason I pulled out the tester was because it was charging slower than usual, which reminded me that I had a tester.
    – Jack
    Mar 22, 2019 at 12:27
  • Is the iPad fully or close to being fully charged when you test? In other words, are you testing both scenarios with the same battery level?
    – Allan
    Mar 22, 2019 at 13:16

2 Answers 2


The 3m (meter) 3rd party cable is the problem here. There are two possibilities:

  • it's for an older iDevice that didn't have or support quick charging (iPods, iPhones, etc.)

  • it's a cheap knockoff where the manufacturer didn't supply the correct chip to request higher power delivery

When selecting a 3rd party (non-genuine) Apple accessory, it's always good to go with known brands - I myself prefer Anker or even Amazon basics.

Understanding power adapters and cables

There's a lot of misunderstanding in the question about the role cables play in the charging process. Let's clear some of that up...

  • The cable itself, doesn't dictate how much power drawn. Two cables of similar AWG (gauge or diameter of the wire) isn't going to draw vastly different amounts of power. For the inherent resistance of the cable to become a factor in dropping power, we start looking at distances in the kilometer range (a thousand times longer than what you're working with).

  • A typical 20 AWG copper cable can support from 4A (multi-core like braided wire) and up to 6A (solid core) of current. At 2A, you are well within the tolerances and "getting warm to the touch" is perfectly normal.

  • There are many differences for the amount of current draw on a device:

    • Load - an idle computer draws less power than one crunching away displaying video
    • Charging state - a fully charged battery draws less power to charge than a depleted one. Also intelligent chargers go from "rapid charge" to "trickle charge" once a threshold has been reached.
    • Power Negotiation - intelligent devices like quality Apple cables or USB 3.1 chargers negotiate the amount of power delivered.

The issue specific to your situation is the last point - power negotiation. In Apple cables - both Apple branded and high quality 3rd party - there is a chip that negotiates with the power brick how much power to deliver

enter image description here Photo courtesy Chipworks

If the chip in the cable only requests 1A of power, the power brick will only deliver 1A of power.

  • Just to make sure, it is likely that my 3m cable chip, only negotiates 1A of current, instead of 2?
    – Jack
    Mar 23, 2019 at 0:05
  • That’s correct. It’s probably for an older iDevice that didn’t support quick charging
    – Allan
    Mar 23, 2019 at 1:25
  • I contacted the seller, and they told me the supplier said that there where 3 types of lightning cables that come from China, 3 pin which is not good ,5 pin which is good enough for sale and 8 pin which is original quality. They told me the one I got was probably the 5 pin which resulted in lower current draw. That doesn't sound right to me, I thought that lightning cables had to be 8 pin. What do you think?
    – Jack
    Mar 25, 2019 at 1:33

If the cable/cord is built into the pronged outlet plug (i.e. the cable cannot be separated from the outlet plug), the difference could be because the device produces a different output current. If this is the case, check the plug end of the cable and look for printed text (it may be small) on the casing. Reading this text should confirm the output voltage/amperage.

However, if your cables are not directly built into the plug end, then your cord that is producing fewer amps is probably dangerous and a fire hazard!

Why? -- If it is not transmitting close to the same current as your other cable/cord, that means the energy that would have been given to your device's battery is instead being dissipated/lost in the cable, probably as heat. In this case, don't use the cable - it could cause a fire and/or damage your electronic device.

Does the cable heat up? Does the cable have any damaged/exposed/frayed wires?

  • 1
    So, basically you're saying, nobody should use USB-A/C chargers because the cable is not built into the transformer portion of the adapter? That's a ton of iPhones, iPods, and iPads that you're claiming all have "fire hazard" chargers included with them.
    – Allan
    Mar 22, 2019 at 1:39
  • 1
    Allan : No and I see why you thought that. I have edited my comment to make it more clear. Mar 22, 2019 at 1:54
  • The 3m cable I bought was a USB to lightning cable, and the USB plug side does not have a rating in it.
    – Jack
    Mar 22, 2019 at 12:34
  • I'm puzzled what you mean by "cord that is producing fewer amps"?
    – bot47
    Mar 22, 2019 at 16:02

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