Review on 🔌 20W USB C Charger Fast Wall Charger Block Plug with 3FT USB C to Lightning Cable for iPhone 13/13Pro/13Mini/13Pro Max/12/12 Mini/12 Pro/12 Pro Max/11/11 Pro/XS/XS Max/ XR/X - iPhone 12 Charger by Shelley Nims

I have a degree in computer electronics and these are simple step-down transformers. When you run electricity through a wire, a magnetic field is created. Conversely, if you run a magnetic field through a wire, you move the electrons in a way that makes step-up and step-down transformers work, or you can make a 1:1 ratio for an isolation transformer. You take a wire and cover it with a material to prevent current from flowing through the wire, so you have a very long wire, but it's wound tightly and this coating prevents the wire from shorting out. Without the coating, the wire would just be a piece of copper. The windings of a coil plugged into an outlet have electrons moving through the wire, creating the magnetic field mentioned. This expanding and contracting magnetic field travels through the second copper coil, and this expanding and contracting field moves electrons in the second coil of wire, which is connected to the USB port that you plug the charger into. Why, if I don't think it worked out - We bought a pair to try and I was so impressed we ended up with 6 of them. 3 failed. I had one that when new charged my 10 inch tablet and my wife's 10 inch tablet while they were both in use which was impressive. Over time, the amount of charge seems to have dropped to the point that even charging a tablet while in use is more than it can handle and the charger doesn't output enough to charge the device and over time the device drains faster than it can charge. . My guess is that the coating that keeps the coiled copper wire from shorting was cheaply made and sections of the wire are no longer properly insulated and due to some sort of short circuit, rather than winding 100 feet of coated copper wire, the short section bypasses part of the Winding, and you get (for example) 50 feet of copper wire, which creates a smaller and weaker magnetic field, allowing the charger to run on less current. Box but not made in a way that I thought would last more than 6 months or so.