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Charging Ports: USB Port Voltage in the 2015's

Scurvey

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Scurvey Enthusiast

Scurvey

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Does anyone on this forum have access to a USB voltage meter? I'd like to understand the Ma voltages that are provided with each of the ports in the 2015 Suburbans and Yukons. I believe standard specification for the USB is 500Ma maximum current, but I understand that sometimes they vary. If you find the results please post. Thanks.

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avgas Enthusiast

avgas

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I own a 2014 gmc crewcab so I'm not much help but see if you can find yourself a Charge doctor either on line or at a local shop. It's a small device with a LED display that shows voltage and current draw. It plugs into the USB port then you plug your device into it. I picked up a few on e bay for a couple of bucks each. They are very handy.

 

 

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Scurvey Enthusiast

Scurvey

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What are you trying to determine?

 

Voltage will be constant, the current will vary and will max out at 500mA depending on the load connected.

 

Just trying to determine how long I could expect to charge my iPhone using one of these ports vs connecting my standard iphone charger to the 110v port in the 2nd row and running the cable to the front. I have heard manufacturers don't always respect the 500mA limits.

 

I really wish they would provide a 110v in the front.

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ember1205 Senior Enthusiast

ember1205

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Got ya.

 

Battery charging is governed by the voltage difference between the charging source and the battery to be charged - the larger the difference, the more current that will be drawn to facilitate the charge. Your iPhone came with a charger that's capable of providing a max of 1A of current. Whether you actually draw that much depends on how "dead" the phone is when you start (that will be the highest draw rate) and the quality of the cable you're using.

 

My experience is that charging rate on the 12V or the USB plug in the truck is about the same, and it seems to compare closely with the charging rate on the OEM charger and cable as well.

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avgas Enthusiast

avgas

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I can verify that my 2014 crewcab charges 1amp 5 volts. with my iPhone at 26% battery as I type this out. I don't see why there would be any difference in your vehicle.

 

 

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Scurvey Enthusiast

Scurvey

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I can verify that my 2014 crewcab charges 1amp 5 volts. with my iPhone at 26% battery as I type this out. I don't see why there would be any difference in your vehicle.

 

 

Sent from my iPhone using Tapatalk

 

Cool, so its better to just use the USB charging. Thanks!

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ember1205 Senior Enthusiast

ember1205

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I can verify that my 2014 crewcab charges 1amp 5 volts. with my iPhone at 26% battery as I type this out. I don't see why there would be any difference in your vehicle.

 

 

Sent from my iPhone using Tapatalk

 

How do you "know" it's charging at 1A? You would need actual metering equipment, and not just an "app", to determine the current flow. The 1A charger that came with my phone never gets warm when charging my phone. But, when I plug the iPad into it, it gets warm and the iPad charges much more slowly than when I use the larger brick that came with it. So, you could infer that the iPad draws enough current to run the full 1A of capability of the charger while the phone does not.

 

 

In doing some additional digging, the ports -should- be limited to 500mA of output since they would be deemed as "Data Ports" and the standard current level on a data port is 500mA. Only dedicated charging ports (with no data connectors on the middle two pins) are able to output as much as 1500mA.

 

It's possible that the draw level of the device could overrun the spec of the port, but that's hard to know for absolute certain.

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avgas Enthusiast

avgas

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GMC USB

Here is proof.

I have a meter that plugs into the USB port that shows me the voltage and current draw so I can tell you 100% that my statement above is correct.


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ember1205 Senior Enthusiast

ember1205

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That's interesting...

 

I've been doing some testing of my own. I have a Kill-A-Watt meter and am using that to monitor the current draw. The Kill-A-Watt shows a variety of different measurements, but for this monitoring I opted to use the "VA" monitor as it would allow for the simplest math with the most accuracy. Keep in mind that a Watt is exactly the same as a VA since the formula is W=VxA.

 

The factory iPhone 6 charger is 5W, or 5VA. Plugging in the iPhone 6 with under 20% charge remaining, the Kill-A-Watt shows a VA draw of between 10.2 and 10.4. That's DOUBLE the rating of the OEM charger at 2.08A!

 

Since your meter is showing a solid 1A, it would appear that the USB ports in the truck are actually capable of double the wattage that they are rated for. What I would be interested in knowing is this:

 

If you hit the Media button on the radio so that the phone is now connected via USB as a data device, does the amperage drop to .5 or stay at 1.0?

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avgas Enthusiast

avgas

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The current draw remains at 1A DC while the radio is on key out of the ignition. In media mode it goes to 0.99A.

 

The USB ports are not powered when the truck is off. They do come alive when a door is opened but don't stay powered on for long. During this power up they only output 0.51A DC.

 

If I plug my iPhone charger into my kill a watt meter it shows a current draw of 0.05A AC

 

The iPhone 5 chargers are rated at 1A DC output

 

The iPad 2 charger is rated at 2A DC output

 

I went to the truck and verified this just now so the USB ports appear to have a 1A DC output.

 

I also tried my iPad in the truck and the meter showed 1 Amp. If I bring it in the house and plug it into the 2 Amp charger it does charge at 2 Amps. This would tell me that the meter is pretty accurate.

 

 

Sent from my iPhone using Tapatalk

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ember1205 Senior Enthusiast

ember1205

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1A DC output is 5W (it's a 5VDC output at 1A). That same 5VDC on the USB port in your truck is running the same 5W (1A) of output even though it is considered a Data Port and is supposed to only supply a maximum of 2.5W of power (500mA).

 

Even a USB 3.0 plus is only rated to supply 4.5W of power.

 

Now, if these are "CDP" (charging downstream ports), supporting higher capacity charging AND data transfers, then supplying a full 5W of power is reasonable. It would be interesting to see if the amperage drops to .90A when accessing data on the phone as that's what the standard says is supposed to happen.

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Scurvey Enthusiast

Scurvey

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Very interesting stuff. I think the iPad chargers are rated for 5V and 2.1AMPS. Evidence is supporting what I had hoped for, that there is some intelligence behind these port chargers.

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ember1205 Senior Enthusiast

ember1205

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Actually, read the USB spec.. Intelligence to understand what USB spec is in use by the powered device is necessary and the charger won't supply more than 100mA until digitally negotiating the proper configuration with the powered device. Or, something like that. lol

 

It's late.. I'm tired.

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