What's the min voltage to trigger the "charging" message on the iPad?

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sigmet Author

Level 1

5 points

What's the min voltage to trigger the "charging" message on the iPad?

Hi,

I know the provided voltage is 5v from the power adapter.

I know the [iphone] battery requires about 3.7 to get the job done. Not sure about the iPad.

Is there a point on the iPad prior to (iPhone 3.7) where the voltage triggers the "charging" message on the screen?

I ask because I fly several aircraft that have an onboard approved USB charging port that is both approved by the FAA and stamped with "made for iPad" on it.

However, they act differently.

Some will show "charging" but the battery percentage will not increase--even if all apps are closed--and just remain at the same state of charge.

Some will show "charging" but the battery percentage will actually decrease--regardless of the number of apps open.

So, this makes me think there is a voltage that triggers the charging message, but it's not quite to the (3.7 in the case of iPhone) necessary voltage needed to actually draw the current.

Finally,

What, if any, amps will the iPad draw if the voltage isn't proper?

Posted on Sep 6, 2018 11:00 AM

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Answer 1

Top-ranking reply

rockmyplimsoul

Level 6

11,161 points

Sep 6, 2018 5:40 PM in response to sigmet

It is not the voltage, it is the current capacity of the source. A USB source is always right around 5 Volts, even under rated load.

The problem is certainly insufficient current -- an iPad requires more current than an iPhone, which is why it is sold with a 10 Watt adapter (which can source up to 2A ... the iPad will pull whatever it needs up to 2A) and an iPhone comes with a 5 Watt adapter.

Despite the "Made for iPad" label, I suspect that the aircraft's USB source is limited to 1A (or even less), which is fine for an iPhone but not quite enough for an iPad. An iPad will charge at 1A, but slowly (and the battery will actually deplete if the iPad's screen is on). To test this, you can get an inexpensive inline USB multi-meter, for example:

Amazon.com: X-DRAGON USB 2.0 Digital Multimeter Power Meter Tester Current and Voltage Monitor, Test Speed of Chargers, …

The other possibility is a defective Lightning cable (or a non-Apple branded one which is not "Made for iPhone" rated).

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Answer 2

jh.3

Level 1

65 points

Sep 6, 2018 11:07 AM in response to sigmet

Hi sigmet,

Although I do not know much about this topic or charging and electricity, I have an idea. My guess would be the minimum required wattage of the power adapter/source should be greater than or equal to the adapter that came with your iPad. This depends on the iPad, as different models come with different adapters.

I am sorry if this was of no use, but I thought it may be worth giving my guess regardless!

Hope this helped in some way!

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What's the min voltage to trigger the "charging" message on the iPad?

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