Can an iPhone fast charge? Channel 7 GadgetGuy Val Quinn put four iPhone XS Max and different genuine Apple chargers to the test. The answer is yes, and no!

Short answer – an iPhone can fast charge if it is an 8 or later (X, XR, XS), but not with the 5W (5V/1A) charger supplied in the box.

an iPhone fast charge

You can view the news article here.

What is Apple iPhone fast charge?

The iPhone 8 or later accepts up to 7.5W (5V/1.5A) to charge its internal 3.8V battery. The battery mAh capacity (how many milliamps it can supply for an hour) is

  • 8                     1812
  • 8 Plus            2691
  • X                     2716
  • XR                  2942
  • XS                   2658
  • XS Max         3174     

In theory, if your phone uses around 200mA per hour, you divide the mAh capacity (think of a battery as a bucket of energy) by the energy use (mA) to give you the total usable time.

Using the bucket analogy, you can charge (pour in energy) as fast as the bucket’s ‘mouth’ accepts it without spilling everywhere. Apple limits the iPhone 8 or later to 7.5W (5V/1.5A). It does that for safety reasons – 7.5W charging does not overstress the battery, but other brands are very happy to fast charge at double or treble that wattage with no apparent issues.

Apple iPhone 8 or later support faster charging using an implementation of the USB Power Delivery (USB-PD) standard that is a subset of Qualcomm quick charge 4/+ and used by Samsung 15W, Huawei Turbo Charge, OPPO VOOC et al. USB-PD is only for USB-C devices.

Chargers

Apple supplies a 5V/1A (5W) charger in the box. It costs $29 as an accessory. This is clearly under capacity, and it’s disappointing that such an expensive device has an inadequate charger. It also uses a USB-A to Lightning proprietary connector cable.

This charger can take up to eight hours to go from 0-100% on an iPhone XS Max – it is faster if the phone is switched off. It is unable to keep up with the power draw for heavy users.

There are other Apple chargers that come as accessories or with various devices. The catch 22 is that these may require an expensive USB-C to Lightning cable which is currently $29 for 1 metre and $55 for two metres.

  • 12W USB-A to Lightning 5V/2.4A – $29 (non-USB-PD but delivers more wattage to charge faster)
  • 18W USB-C power adaptor – $49 (also available in the box with latest 11 and 12.9in iPad Pros)
  • 30W USB-C power adaptor – $69 (also available with MacBook and MacBook Air laptops)
  • 61W USB-C power adaptor – $99 (also available with 13in MacBook Pro laptops)
  • 87W USB-C power adaptor – $119 (also available with 15in MacBook Pro laptops) NOT TESTED
an iPhone fast charge

What effect do these have?

We discharged four Apple iPhone XS Max (supplied by Apple) to 0% and started the charging process using the 5/18/30/61W adapters.

The results were surprising – well actually not to a techie, but we will explain why later.

CHARGER 5W (5V/1A)
Non-USB-PD
18W
USB-PD
30W
USB-PD
61W
USB-PD
15 min 8% 26% 29% 23%
30 min 17% 50% 53% 52%
45 min 25% 72% 73% 70%
60 min 33% 81% 82% 81%
90 min 50% 95% 96% 95%

Back to the bucket analogy.

The 5W charger really struggles to fill the bucket faster than the iPhone uses energy. If you use this charger make sure you switch off the iPhone while charging.

With USB-PD standards, the battery charges in stages to prevent overheating. Initially, it pushes up to 20V, then tapers down to lower voltages and at about 80% tops up with 5V. The charger and phone have a circuit to ensure delivery of just the right mix of volts/amps to avoid battery stress.

So due to the 5V/1.5A limit (7.5W), a 12W (not tested) or the 18W (tested) is all you need to achieve faster charging – a full battery in under two hours. Larger wattage chargers make no difference so don’t waste money on them if you are just using it on an iPhone!