Amperage and Voltage Limits of the Regular USB-A Lightning Cable?

A standard USB Type-A Power Adapter will always charge at 5V. Most Apple devices charging from a USB Type-A power source are limited to ~12W (i.e., 2.4A @5V).

Many recent models of iPhone that use a Lightning connection can fast-charge when connected via a suitable cable to a USB-C power source that supports USB PD (Power Delivery). These devices typically limit charging to ~20W. When using a USB PD compliant power source, it is the Power Delivery protocol that determines the charging voltage supplied by the power source to the load. USB PD actively negotiates a the highest mutually supported power profile of the power source, connected device(s) and cable - and hence the bus voltage used by the Power Adapter and connected device(s).

A power cable's power handling is principally determined by the cross-sectional area of the individual wire conductors within the cable, the larger the wires, the more current the wire can carry before burning-out like a fuse. Power is calculated by multiplying current by voltage (i.e., V x A = W). As such, increasing the voltage allows the same power to be transferred at a lower current.

USB-C cables are rated by their power-transfer capabilities - not by voltage - as the charging current and voltage may differ. As such, while a changing cable rated to carry high power will be perfectly usable with devices that do require much power, the increased cost of these cables are uneconomic unless also being used with other devices that can benefit from greater power capacity of the cable.

Also consider that certified USB-C cables are "active" - as they themselves include electronic components within the USB-C connectors. As well as managing USB-C data communication, the active electronics within the cable also safely limits power transfer for that cable.

Hopefully you now have a better understanding of the differences between USB interfaces and their potential impact upon device charging.

Apple has never publicly documented the voltage and amperage ratings associated with Lightning.

For details, you’ll likely need to join MFi: MFi Program - Apple Developer

MFi-certified Lightning cables are all intended to be interchangeable.

For non-MFi certified cables, who knows?

For information on the USB-A or USB-C supply connection, check the associated hardware documentation.

Here is how to: Fast charge your iPhone - Apple Support (requires iPhone 8 or newer)

Alvin777 wrote:

I guess I can use the regular Apple made Lightning cables on the 2.4A USB charge only port (no data, I wish it did though). Does this make Apple's cables since the iPhone 1 fast charging cables since it can do 5v at 2.4A or this only started with Lightning?

Some terminology: USB is a family of standards, both communications protocols (USB 2.0, USB 3.x, USB4, etc.), and connectors including USB-A, USB-B, and USB-C.

USB-C connectors in particular can be used with very different protocols, including but not limited to USB communications protocols, with USB power delivery protocols, and with Thunderbolt, DisplayPort and other protocols. All USB protocol connections have some power available, but the details will vary.

For USB power delivery, the USB power source and the device negotiate the best available choice for power.

Barring any cable damage or other such cases, any Apple or MFi-certified Lightning cable is utterly irrelevant to iPhone or iPad power negotiations, whether the Lightning cable uses a USB-A or USB-C connector. They all work the same.

This as differentiated from Lightning-related cables, USB-C USB cables (USB-C to USB-C) are available with 60 watts, 5 amps / 100 watts, or 240 watts capacity. The cable capacity is factored into the USB-C power delivery negotiations.

USB-C ports with Thunderbolt capabilities can also deliver power and communications to USB-C Thunderbolt devices, though that requires a USB-C to USB-C Thunderbolt cable.

By the way how about Apple rare, black, braided USB-C to Lightning, what's the amperage of that and how many watts can it take without being damaged?

As much as an iPhone can appropriately consume, based on the available power supply on the other end of the cable.

TL;DR: cables work, or they don’t. It is exceedingly rare to encounter any issues with a cable, absent some sort of mechanical damage, or some cheap junk-grade (uncertified) cables. Cables for different protocols can use the same USB-C connectors, but different cables can permit connections to work, or (with the wrong cable) can block communications. Not working here means not working, and not smoke- or flame- or other excitement-producing effects.