iPhone Questions

Factual Questions
1

I have a new recent model phone which comes with a lightning cable. I had my previous phone for many years which was charged using a 5V magnetic disc and a USB cable plugging into a 1A or 2.1A adaptor. I presume the power to the phone is the product of the output current and the disc voltage. (If you think not, then what?).

  1. Is this basically linear? Would the phone charge six times faster using a 15W disc and an adaptor with twice the output current?

  2. What are the maxima? What do you use?

  3. Could you use both the lightning cable and the disc? Would this further increase speeds? To what limiting factors?

  4. Since house voltage is higher, is it true a 5V and 15V disc essentially cost the same to make and are being deliberately slowed to allow for a range of products (5V, 10V, 15V) at different price points? Or is this not so?

2

Apologize if these questions are too basic? Surprisingly, my Google-fu is weak today.

3

I think this is the best article for you:

I assume at least when you mention charging via a 5V disc you’re referring to a wireless charger, and should make sure it’s compatible with your iPhone model (since we have no details on either the charger or the model).

But the short answer is that if you use both, most models go with the wired charging only, and the phone will not sustain max charging due to internal heat management. To know more, we’d need more details. :slight_smile:

4

That answers the third question nicely. Thanks for the article.

5

Also, what is the fastest an IPhone could theoretically go from zero to 100%? 50%?

(An article I looked at quoted values for both these points for a specific product, implying that the process is non-linear, as one would expect.)

6

Any other insightful posters? (Bump.)

7

All of the thing you ask have complicated answers, and will depend a great deal on the exact model of phone you’re talking about.

Modern phone charge times are not linear. They will be slow at the very low end and the very top end, and may be very fast in the middle of the battery’s charge. Charging speed will also be limited by temperature, with the battery being very cold or very hot also slowing down charging. This is all done to protect the battery. That is assuming a charger that can charge the phone at its highest speed. If the charger is low power, then the phone might be below its “safe” charging rate across the entire charge range.

Many phones will advertise something like “30 minutes to charge from 20-80%,” and it might take another 30 minutes to go from 80% to full. If you have a kill-a-watt or a USB power meter attached to the charger you can see the voltage and amperage move up and down during the charging cycle.

There are also lots of different ways that USB chargers and devices communicate how much power to provide. Default USB maxes out at 5 volts and 0.5 amps (500 mA). To get more power than that, the charger and the device have to discuss it. Sometimes the discussion is as simple as putting a voltage on one of the USB data lines, or a resistance between some of the lines. So that leads to things like Apples 2 amp charging, Qualcom’s Quickcharge system, and USB-PD (power delivery).

I believe modern Apple devices can speak the old 2 amp language, and USB-PD. The fastest charger I have for my ipad is an 18W USB-C PD charger that came with my Google Pixel phone. It is much faster than the 10 watt (or whatever it is) charger that came with my iPad.

Quickcharge and USB-PD adjust both the voltage and amperage to provide more power than default USB.

Wireless charging is similarly complex, with a variety of different standards used to deliver more power. Both the wireless charging pad, the charging adapter it is plugged into, and the device being charged all have to agree on how much power will be sent.

So, there is a real difference between a 5 volt and a 15 volt charging pad. The electronics in the pad need to support the higher voltage, and have the right smarts to negotiate with the device and charger to get the extra power. There may also be licensing fees to use some of the higher power charging methods.

So, it is far more complex than plugging a 9 watt lightbulb or a 1500 watt space heater into the same wall receptacle, and getting whatever amperage is necessary, relying only on Ohm’s law (or whatever electrical thing makes electricity flow at the right amperage).

8

Or you can use an app.

(There are probably iPhone versions, too.)