Sorry I didn't have time this past weekend to make a video. I think I will be able to do it this weekend.
This is the circuit for 2A max current draw:
- The voltage at the USB connector should be 5.10 to 5.20 volts. Most power supplies have an internal trim pot to tweak the output voltage.
- Use the USB cable that came with the iPad. Don't use a generic cable or another Apple cable.
- The MAXIMUM current draw is 2 amps. It will usually be much less.
- The highest current draw will usually be when the battery is 20% to 70% charged. The charge rate slows as the battery reaches full charge. If the battery is 80% charged or more, there will not be much current draw.
- Use an amp meter (or bench supply with amp meter) to determine if this is working properly. Don't rely on the iPad's charging indicator.
Here is a picture of the resistors in an iPad 10 watt (2 amp) charger:
These are 1% resistors, so the markings are a code
, not the literal resistance.
The 'C' suffix means multiply by 100.
62 = 432, so 62C = 43.2k
68 = 499, so 68C = 49.9k
85 = 750, so 85C = 75.0k