Hi all, got a question about provided voltages.

I have this:

https://www.amazon.com/gp/product/B00ORNOWZK/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

I plugged it into an iPhone charging adapter and got 5.08V.
I then applied the load of an iPhone to which the voltage dropped to 4.65 and the amps hovered somewhere around .7 (around 90% charged).

Shouldn't the iPhone power adapter work to keep 5V constant inside the cube there? I thought that is what the purpose for it.
I also went from 5V to 4.5 on a random USB charging port that was designed for iPhone use.

I've never noticed this before to ask, but why is it I don't see voltage drops in my house's outlets with all those consumers, but a single phone can make it appear to drop by about 5%?

 

ok, I haven't any where I am right now. Would that have an impact?

 

On second thought, a drop of that much may be the result of internal circuitry. Regrettably, ... not familiar enough to advise.

 

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(Some text removed for clarity)

I've never noticed this before to ask, but why is it I don't see voltage drops in my house's outlets with all those consumers, but a single phone can make it appear to drop by about 5%?

Yes if there is a cable between the port and the load. As I recall this voltage drop (of something like 10%) was discussed in the USB 1.0 standard.

 

Is it a genuine iPhone charger? Some of the copies are absolutely horrible - very crude design that would result in poor regulation and unsafe to boot. It is normal to see some voltage drop with load, but what you are seeing seems excessive, provided that the meter is plugged directly into the charger.

These meters are useful for evaluating the voltage drop in a cable if you have suitable adapters (which can also introduce some drop). If you first plug the meter directly into the power source and the cable (with load) into the meter, then move the cable to being between the meter and the power source you can determine the voltage drop in the cable.

 

Is it a genuine iPhone charger? Some of the copies are absolutely horrible - very crude design that would result in poor regulation and unsafe to boot. It is normal to see some voltage drop with load, but what you are seeing seems excessive, provided that the meter is plugged directly into the charger.

These meters are useful for evaluating the voltage drop in a cable if you have suitable adapters (which can also introduce some drop). If you first plug the meter directly into the power source and the cable (with load) into the meter, then move the cable to being between the meter and the power source you can determine the voltage drop in the cable.

Hi. It’s MFI by an aerospace company. Even if i plugged the usb meter into the iPhone cube adapter, then put the iPhone into the meter’s USB ports I see the voltage drop.

The operating current of the meter is 20ma if I recall.

The Apple little cube puts out 5 but the batter only need 3.7.

 

Some cheap USB cables use really small wire. A quality cable uses larger wire and, so, will have lower resistance and less voltage drop.

A friend found that some cables were not good enough to supply power to his Raspberry Pi and its display at the same time.

 

Interesting. Makes sense, but I'm using OEM cables here.

I think there might be an issue with the usb meter. it will allow an iPhone to charge using the 5W cube, but it won't allow an iPad using the 12W adapter.