iPad Pro Yes, the iPad Pro charges SLOWLY. Here’s why.

[rkuo]

It is an educated guess. Things like voltage are messy. Variable voltage needs to be managed well, which means more complexity to something that is already complex. USB PD requires a negotiation handshake and circuitry to handle the variable voltage. Neither of these reside in the cable, and so you tend to need cables built for whatever current this might wind up entailing.

But here's the thing, let's assume I am 100% wrong and Apple can push 12V on the pin in a similar way. Hooking up more voltage to a 3.3V battery does nothing for your charge speed. Charge speed is entirely determined by current. So if you've upped the voltage, but still can't move more than 2.4A across the wire because the wire is too thin to carry more, you've fiddled with things for zero gain. Input voltage is determined by the battery voltage you want to charge. 12V on USB C is important because laptop batteries tend to be ~8-11V to run the 5V circuitry. ARM gets away with 3.3V which is more flexible in mobile devices.

The other problem is that yes you do need more pins for USB3 (and the iPad Pro has them). Data speed is a mix of a couple things:
1) How many pins you have for data (each pin transmits one bit per clock cycle)
2) How fast your clock is

And contrary to what a lot of non-engineers tend to believe, you can't just push the clock speed over the wire higher and higher. You get more and more noise that screws up your signal, crosstalk, and other fun things because fast moving electrons generate magnetic fields that then mess up how other fast moving electrons travel. So to get the sort of data USB3 pushes, they had to add more pins to carry data. That reversible USB C connector? USB 3 uses both sides. And if lightning wants to carry USB3 over it, it is going to need to do one of two things:
1) Use both sides of the plug to double the pin count.
2) Use an expensive active cable where it converts USB 3 into something proprietary, running at a higher clock speed with fewer pins to talk with the iPad itself.

And if you look inside the lightning port on the iPad Pro, and compare it to the Air 2, the Pro has connections for both sides of the lightning cable, while the Air 2 only has connections for one side. So it's pretty clear Apple went with #1.

A USB 3.0 connector has 9 pins to maintain *wire to wire* compatibility with usb 2.0 and still support usb 3.0 on the same connector. If you are not trying to maintain that (and it is absolutely not necessary for a lightning connector to do so) then Apple can just use two signal pairs to get usb 3.0 speeds, ignore the usb 2.0 pair, and possibly perform some extra translation in whatever adapter they end up making, coming in under the 9 pin count.

Coincidentally I just ran across this blog which in fact discusses exactly what I just said above. http://brockerhoff.net/blog/

Regarding voltage, your language is confusing and seems to indicate some unfamiliarity with the basics. Ultimately the PMIC (power management ic) in the phone will control the charge rate to the battery, and it is absolutely possible for a PMIC to benefit from a higher input voltage at the same current, which fundamentally increases the power sent over the same wire and can be transformed to the correct voltage and amps for optimal charging. Higher voltages are expressly used for transmitting more power over a "thinner" wire while still maintaining the same current. This is how power is transmitted all over the world and, indeed, into your own home.

 

[LunaC]

I was pointing out that upping wattage by upping voltage while leaving current constant buys you nothing when trying to charge a battery, as the poster suggested that I was responding to (9/12V with 2.4A).

There are multiple ways to accomplish it but you will find a lot of the DC-DC converters used in electronics can do it. It already has to drop the 5v in to ~4.2v and with it comes an increase in current. High speed switching allows for smaller on chip ability with the old-timer monster transformers. since wattage=amperage*voltage, you can easily solve for possible current. Double the voltage in with the same input current and DC-DC can almost double the current (almost because of losses)

Whether or not apple designed it such, no telling but the iPP uses the FDMC 668. I think it has a 30v max in offhand.

 

[garyleecn]

So, it doesn't really work this way. Wattage is a measure of power, sure, but it is current that charges a battery. Not voltage. 5V is fine for charging the 3.3V batteries that are used in the iPad. Upping it to 9V doesn't change anything so long as you can only draw 2.4A. You can have fun with transformers, where 9V @ 2.4A flows over the cable, and then you down step the voltage which gives you more current to play with, but then you are talking about needing two power transformers (which aren't small). One at the wall, and one in the iPad itself on the other side of the lightning cable.

And again, this is all somewhat moot as lightning as a spec assumes 5V on the bus voltage pin(s), and I'm not sure how well protected existing devices would be from over voltage to avoid drawing more current than anticipated. I would hope they are, but usually you don't write a spec for voltage and then violate it later. It is a bit like crossing the streams.

What is hopeful though is that the Pro does have more pins in its lightning port than the iPad Air 2 (i just took a look at both). The Air only has pins on one side of the port, while the Pro has them on both. This is probably what enables the future USB3 support. And it may also enable faster charging by being able to pull more current across multiple pins. That is part of the secret to USB3's faster charging. But even that needs a new cable. Yay.

I don't know the technology behind this, but Qualcomm quick charge uses 9v 2amp to speed up the charging, why can't apple just increase the voltage?

 

[nfl46]

Yeah, the slow charging on Apple devices is annoying. I use an iPad charger for my iPhone but it still doesn't charge nearly as fast as my Android phones. Quick/turbo charging is really nice to have on Android devices.

 

[Newtons Apple]

Does not matter to most as they would charge overnight.

I do not think I have used a full battery on my Pro in a single day.

 

[magbarn]

So, it doesn't really work this way. Wattage is a measure of power, sure, but it is current that charges a battery. Not voltage. 5V is fine for charging the 3.3V batteries that are used in the iPad. Upping it to 9V doesn't change anything so long as you can only draw 2.4A. You can have fun with transformers, where 9V @ 2.4A flows over the cable, and then you down step the voltage which gives you more current to play with, but then you are talking about needing two power transformers (which aren't small). One at the wall, and one in the iPad itself on the other side of the lightning cable.

And again, this is all somewhat moot as lightning as a spec assumes 5V on the bus voltage pin(s), and I'm not sure how well protected existing devices would be from over voltage to avoid drawing more current than anticipated. I would hope they are, but usually you don't write a spec for voltage and then violate it later. It is a bit like crossing the streams.

What is hopeful though is that the Pro does have more pins in its lightning port than the iPad Air 2 (i just took a look at both). The Air only has pins on one side of the port, while the Pro has them on both. This is probably what enables the future USB3 support. And it may also enable faster charging by being able to pull more current across multiple pins. That is part of the secret to USB3's faster charging. But even that needs a new cable. Yay.

I think you need to read up on electricity again. The vast majority of devices that support higher USB charge speeds with higher voltage like Qualcomm's quick charge use a higher voltage to faster charge a 3.3V single cell lipo battery. 5Vx2.4A=12 watts, 9Vx2.4=21.6 watts. The circuitry on the phone steps down the voltage internally to the battery's charge voltage. The advantage of the higher voltage is the ability to carry more watts through a thinner wire/connector. I see the same effect all the time when I charge my RC helicopter batteries. My charger can charge at 1300 watts. If I feed it only 12 volts, the 10 gauge cables I use get very hot along with the connectors. When I connect the charger to a 24 volt power supply, the wires are barely above room temperature. Mind you, I'm still charging 3.3 volt lipo batteries to 4.2 volts at 1300 watts and at 4C which charges them in 15 minutes in either case wether I'm feeding the charger 12 or 24 volts. It's just that I'm drawing double the amperage through the wires to get the same amount of watts.

 

[Cordorb]

Thanks for starting the thread.

I use a Whats-up device ( DC Inline Watt Meter and Power Analyzer) and was wondering why it seemed all the Apple charger adapters ( 5 W - 10 W and 12 watts ) were all powering the Ipad Pro at a 1 amp rate.

I forgot about the sense lines Apple puts in devices ( on the data lines ) to give the computer device data on the max power to expect. ( I do solar powered charging and and if you leave out the data lines no need to be a hardware developer)

The Apple Lightning cable interface is adaptive but I thought the power lines just passed in and out ?

The charger chips inside the Ipad have complete control of how much power the device will take from the external power unit and in the past the chips/logic will even NOT allow any battery charging depending on the sense lines.

 

[jamesarm97]

FYI, I think the charger that comes with the new iPad maybe slightly higher than 5v. I remember looking on mine to see what wattage it is to see if it would charge faster than others I had. Twice now I noticed that if I use my iPhone charger or my built in Ac USB outlet charger that the iPad only charges to 94/95% even when left on overnight. If I use the iPad pro charger it charges to 100%. I don't have it in front of me but I that I noted mentally that it said 5.27v on the charger. Could it by the iPad pro won't charge fully from a standard charger or is it just a fluke? I'll check my charger again tomorrow.

 

[echo1877]

FYI, I think the charger that comes with the new iPad maybe slightly higher than 5v. I remember looking on mine to see what wattage it is to see if it would charge faster than others I had. Twice now I noticed that if I use my iPhone charger or my built in Ac USB outlet charger that the iPad only charges to 94/95% even when left on overnight. If I use the iPad pro charger it charges to 100%. I don't have it in front of me but I that I noted mentally that it said 5.27v on the charger. Could it by the iPad pro won't charge fully from a standard charger or is it just a fluke? I'll check my charger again tomorrow.

Happy to give you a free coupon to my app to compare the differences and post them. My app will show you actual charging performance for any charger you use.

 

[masotime]

Happy to give you a free coupon to my app to compare the differences and post them. My app will show you actual charging performance for any charger you use.

Huh! I didn't know you had an actual app. Just bought it....

EDIT: Pretty useful. I thought only Android allowed access to all the system information internals. I assume this is accurate? It's good to have an accurate way to determine exactly how fast my iOS device is charging...

EDIT 2: Lol I must have skimmed past the first line of your original post. Nevermind.

 

[jamesarm97]

Happy to give you a free coupon to my app to compare the differences and post them. My app will show you actual charging performance for any charger you use.

Sure. PM the code if you want and I will check the differences in the Chargers. Does it see the voltage also or just current / charge time?

 

[rkuo]

FYI, I think the charger that comes with the new iPad maybe slightly higher than 5v. I remember looking on mine to see what wattage it is to see if it would charge faster than others I had. Twice now I noticed that if I use my iPhone charger or my built in Ac USB outlet charger that the iPad only charges to 94/95% even when left on overnight. If I use the iPad pro charger it charges to 100%. I don't have it in front of me but I that I noted mentally that it said 5.27v on the charger. Could it by the iPad pro won't charge fully from a standard charger or is it just a fluke? I'll check my charger again tomorrow.

The 12W charger has always been 5.2V. That's how it manages to stay in spec. USB has a range of tolerance around 5V and the trick was to simply go to the upper range of that tolerance to squeeze out 12W instead of just 10W like the older charger.

 

[Krevnik]

There are multiple ways to accomplish it but you will find a lot of the DC-DC converters used in electronics can do it. It already has to drop the 5v in to ~4.2v and with it comes an increase in current. High speed switching allows for smaller on chip ability with the old-timer monster transformers.

Yup, you've got me here. Admittedly my electronics knowledge is from a ways back (sadly), and apparently the state of the art when dealing in this space has moved on quite a bit from what I was actively doing work on the hardware side of things. Sad that these papers that have lead to this are still quite old (around the time I moved away from the really old embedded world).

I think you need to read up on electricity again. The vast majority of devices that support higher USB charge speeds with higher voltage like Qualcomm's quick charge use a higher voltage to faster charge a 3.3V single cell lipo battery. 5Vx2.4A=12 watts, 9Vx2.4=21.6 watts. The circuitry on the phone steps down the voltage internally to the battery's charge voltage.

Although this argument is kinda terrible, because it's basically telling me: "You can use a transformer!" (using the RC charger as an example which is not exactly a new concept) when I said as much in my own post. The missing bit was these newer converters were actually preserving the wattage correctly in the DC->DC conversion. Some of the simpler DC->DC linear regulators produce waste heat instead of higher current. Wattage is technically preserved, but waste heat isn't exactly something you can do work with.

 

[newellj]

Well, I don't know for sure obviously. But I can tell you that there are two separate parameters in the power management unit. One is for the DESIRED charging speed (which is 5560mA), and one is for the maximum allowed input current on the Lightning port (which is 2400mA). I don't think this version of the iPP can handle anything beyond 2400mA.

To be clear, I am not suggesting that this is a reason to not get an iPP. I for one love mine. It just doesn't charge very quickly...

Possibly UL/CE approvals, which could be difficult/time-consuming/costly to get changed? That's a pure guess.

 

[echo1877]

EDIT: Pretty useful. I thought only Android allowed access to all the system information internals. I assume this is accurate? It's good to have an accurate way to determine exactly how fast my iOS device is charging...

Thanks! It's very accurate. The data is coming straight from the horse's mouth if you will...

I've measured and verified pretty much every data point in there with various external tests, and none of the data is made up/estimated by the app. It is all coming from the system.

 

[echo1877]

I have a quick update on my original post. Basically, I've detected one new data point in the iPad Pro that I hadn't noticed before. For some reason the software is set up to track TWO external power adapter signals, whereas every other iOS device until the iPP was configured for one.

When you plug-in the 12W adapter, it shows one adapter as 12W, and another as disconnected...

The only theory I can come up with is that this is related to those extra 8 pins on the Lightning connector (which are unique to the iPP AFAIK). It is possible that Apple is planning to release a proprietary adapter and cable that will run two parallel signals in one cable, utilizing all 16-pins on the Lightning connector, thereby doubling the power to around 24W. Such a theoretical cable would likely have no compatibility/safety issues as it would only be able to deliver the 2nd signal to the iPad Pro, whereas other iOS devices would only utilize 8 of the pins.

The combination of the software changes and the 16 pins on the Lightning connector make me feel that this is a likely possibility. Guess we'll find out...

 

[masotime]

By the way, it would be great if you could make your app universal... There's plenty of space on the iPad pro to show all 4 panels simultaneously

 

[echo1877]

Anyone care to guess what the 24W iPad Pro adapter with 2 signal Lightning cable is going to cost? I say $49.

 

[dyt1983]

EDIT 2: Lol I must have skimmed past the first line of your original post. Nevermind.

It wasn't stated originally, and it seemed kinda sketchy to me that he was referencing it without that disclosure.

 

[echo1877]

It wasn't stated originally, and it seemed kinda sketchy to me that he was referencing it without that disclosure.

It was disclosed on the first paragraph of my original post since I first started this thread (check the edit history, if the forums have that). Not sure what you find sketchy exactly.

 

[Cordorb]

Apple indicates the charger type through a proprietary technique of resistances on the USB D+ and D- pins.

To read more see

http://www.righto.com/2012/05/apple-iphone-charger-teardown-quality.html


If the computer gets it wrong and you try to pull too many amps for a charger the ( 5 v) voltage will drop too low and other circuits will come into play.

I have only played around with charging using third party Apple 30 pin USB cable where the resistors were in the 30 pin side.

 

[echo1877]

Apple indicates the charger type through a proprietary technique of resistances on the USB D+ and D- pins.

To read more see

http://www.righto.com/2012/05/apple-iphone-charger-teardown-quality.html


If the computer gets it wrong and you try to pull too many amps for a charger the ( 5 v) voltage will drop too low and other circuits will come into play.

I have only played around with charging using third party Apple 30 pin USB cable where the resistors were in the 30 pin side.

That is correct. This article is the closest I've seen to actually figuring out what they do, but it's pretty obvious when you look at the charger device driver. They use specific voltages on the USB data lines (D+ and D-) for identification. 3rd party MFi power supplies do the exact same thing by the way.

The voltages are as follows:

D+=2.0V,D-=2.0V -> Apple 5W (1000mA) brick, like the one that ships with iPhones
D+=2.7V,D-=2.0V -> Apple 10W (2100mA) brick, like the ones that ship with older iPads
D+=2.7V,D-=2.7V -> Apple 12W (2400mA) brick, like the ones that ship with recent iPads, including iPad Pro

 

[mgipe]

I have a quick update on my original post. Basically, I've detected one new data point in the iPad Pro that I hadn't noticed before. For some reason the software is set up to track TWO external power adapter signals, whereas every other iOS device until the iPP was configured for one.

When you plug-in the 12W adapter, it shows one adapter as 12W, and another as disconnected...

The only theory I can come up with is that this is related to those extra 8 pins on the Lightning connector (which are unique to the iPP AFAIK). It is possible that Apple is planning to release a proprietary adapter and cable that will run two parallel signals in one cable, utilizing all 16-pins on the Lightning connector, thereby doubling the power to around 24W. Such a theoretical cable would likely have no compatibility/safety issues as it would only be able to deliver the 2nd signal to the iPad Pro, whereas other iOS devices would only utilize 8 of the pins.

The combination of the software changes and the 16 pins on the Lightning connector make me feel that this is a likely possibility. Guess we'll find out...

Another possibility is that they are set up to permit charging through the smart keyboard connector.

 

[echo1877]

Another possibility is that they are set up to permit charging through the smart keyboard connector.

There's only one way to find out. Anyone out there with enough electronics/DIY skills to set up a Lightning connector where each side goes to a separate USB cable (plus the willingness to slightly jeopardize your iPP)? That way you could confirm whether two simultaneous 12W feeds are actually supported.

 

[Trickhot3102]

So we’ve all heard that the iPad Pro is slow to charge, but I’ve been doing some research on the actual numbers and have had some interesting findings. I’m the developer of a battery/charging information app on the App Store called Battery Health and so I am often looking at the innards of iOS devices in terms of batteries and power management. This research is based on live stats reported by the internal charger device driver on the iPad Pro.

iOS devices ship with an internal charger chip (that's inside the device, NOT the power adapter that ships with it) that is configured to charge the battery at certain rates, depending on several factors. Battery charging speeds are typically measured by a unit called C, which is basically a fraction of the total capacity of the battery. For example, a 1000mAh battery that charges at 0.5C indicates that we’re charging it with a 500mA current, or half of its capacity. The higher the charging current, the faster the battery gets charged. For most iOS devices, the base charging rate for the constant current stage (the early, fast stage in the charging process) is around 0.55-0.65C.

For example, The iPhone 6 Plus has a 2855mAh battery and it charges at a maximum current of 1730mA, or about 0.60C. The iPhone 6S Plus has a slightly smaller 2725mAh battery, and its maximum charging current is 1790mA, or about 0.65C, so it charges a bit faster than the 6 Plus. Some Android phones will go much faster, up to .80C or even 1C. The catch is that faster charging shortens the overall life of the battery, so quite honestly Apple is playing it very safe with these kind of numbers, which is why their batteries tend to last so long.

Now, the iPad Pro has a gigantic 10,088mAh (38.3W) battery, but its maximum input current at the USB port is only 2400mA (12W, same as all other recent iPads). When you charge an iPad Pro, its charger is configured at 0.55C, same as many other iOS devices. The problem is that with a 10,088mAh battery, that comes to 5560mA, or 28W.

This means that the iPad Pro technically needs a 28W charger to charge at optimal speed — at the INTENDED speed. The 12W charger it ships with is only supplying 40% of the current required to charge it at maximum speed.

What’s more alarming is the fact that if you push the Pro hard (full screen brightness, LTE video streaming, etc.), its current draw sometimes actually reaches 2400mA! This means that you could be plugged in with the 12W Apple brick while using it, and the battery won’t actually get charged.

Note that as best as I can tell, the device is configured for a maximum input current of 2400mA at the Lightening port (again, that’s what the device is reporting), so be wary of any 3rd party chargers that claim to charge it faster than the stock charger. I’ve not seen anything like that, but it seems like a likely scam…

For now, the bottom line is, make sure to charge your iPad Pro while it is in standby with the screen turned off. It will barely charge while being used, even with the 12W charger.

Hello and good afternoon sir! Great in depth look at the charging of an iPad pro! I must say I use your app on my iPhone and iPad and love it!!! keep up the great work!