[turbo2ltr]

So I tested the ports in my 2018.

Each port can easily support over 2A. Seems the voltage start dropping off around 2.2A And hard cut around 2.4A

Both ports acted the same. I only have one variable load tester and I couldn't get my fixed load plugged in due to space limitations, but I plugged my phone into one, it was drawing 1.5A. Ran the test on the other port and it still was able to provide 2.2A. I suspect, knowing the specs of the chip, it could provide 2.2A to both ports simultaneously.

[ember1205]

Interesting info, but the voltage is below 5V on that readout. For powering devices, it would probably peak around 2A but for charging workloads the voltage needs to be higher (so the current will be lower - closer to 1A?).

[turbo2ltr]

Originally Posted by ember1205

Interesting info, but the voltage is below 5V on that readout. For powering devices, it would probably peak around 2A but for charging workloads the voltage needs to be higher (so the current will be lower - closer to 1A?).

Current is current. Lower voltage just means lower power (watts) delivered. You can expect to have that drop across most USB cables at that current level. Most USB meters are installed at the charger end of the cable, so you don't measure the voltage drop the phone actually sees. In this case the variable load is measuring at the load (phone) side of the cable.

Here are some pictures testing an Anker 2.4A charger. The variable load is at the end (where the phone would be) and obviously the little blue meter is plugged into the charger.

First is no load. Then near the limit. Notice the source does not drop voltage under load, but the current flowing causes the voltage to drop at the other end. This is normal. I used the same cable for the test in the car.

The charger has no reference to the voltage at the other end of the cable so it has no ability to compensate it's output voltage. It only knows what is on its output. Outside of USB, it is not uncommon for battery chargers for commercial systems to have a "sense" line in addition to the main high current charging wires. The sense line allows the charger to read the voltage at the batteries through a wire that isn't carrying a ton of current. This allows it to get an accurate reading right at the batteries, compensate for the voltage drop and charge the batteries to the proper voltage. Obviously phones don't have that , mostly because the voltage doesn't really matter (to a point) as internally, the phone has it's own switching boost power supply to generate the voltage it needs to charge the batteries. (batteries aren't 5V). As long as the power is available (voltage times current) then it will charge.

I will say that not all cables are created equal. Some will drop more than others under load (smaller wires).. If you've ever powered a raspberry pi with a crappy cable, you know what I'm talking about. hah.

[ember1205]

USB2.0 Spec has a strict limit of 500mA @ 5V for a total of 2.5W. Charging Ports (like in your Anker adapter) can go much higher. The fact that your test device shows what equates to be over 10W of power means that either something is off or the ports are capable of functioning as Charging Ports. And what could be off is that the ports are not actually built to proper USB2.0 spec.

Charging Ports achieve the high wattage by increasing the voltage along with a modest increase in current. 10W from a USB port at less than 5VDC seems like something is malfunctioning (or your test device is overdrawing the ports which have no limiter on them - this could be why many people are seeing their USB ports fail in their cars).

[turbo2ltr]

I think you might be confused two different things.

USB 2.0 spec (Table 7.7) says to meet the spec, it has to be able to provide "at least" 500mA. Meaning the voltage has to remain in spec for up to a 500mA draw. It also states devices must not draw more than 500mA. But having the ability to provide more current than the spec doesn't make it out of spec. Also the spec actually talks about voltage drop and states allowances for it.

Why would the ports in the car NOT be charging ports? That's one of the main reasons they are there for.


There are is only one USB port voltage that does not require some sort of advanced data handshake and that is 5V. And that's 5V nominal meaning it doesn't have to be exactly 5.00V. Some variance is expected, because physics.

I think you are confusing the Samsung fast charge port protocol which, after a data handshake, will raise the output voltage of the charger to 9V. This helps lower the current (and therefore the voltage drop across the cable) while actually increasing the delivered power. Only certain chargers are capable of delivering this, and only certain devices can take advantage of it.

5V * 2A = 10W
5V * 3A = 15W (USB 3.1 standard)
9V * 1.67A = 15W (Samsung fast charge)

There is even a USB-C PD spec that can deliver up to 20V @ 5A (100W!) after the device negotiates a "power delivery contract" with the charger.

Attached the standard 5V 2.4A Anker to my Samsung tablet, and the same tablet connected to a Samsung charger capable of their fast charge protocol.

[ember1205]

Originally Posted by turbo2ltr

I think you might be confused two different things.

USB 2.0 spec (Table 7.7) says to meet the spec, it has to be able to provide "at least" 500mA. Meaning the voltage has to remain in spec for up to a 500mA draw. It also states devices must not draw more than 500mA. But having the ability to provide more current than the spec doesn't make it out of spec. Also the spec actually talks about voltage drop and states allowances for it.

Why would the ports in the car NOT be charging ports? That's one of the main reasons they are there for.


There are is only one USB port voltage that does not require some sort of advanced data handshake and that is 5V. And that's 5V nominal meaning it doesn't have to be exactly 5.00V. Some variance is expected, because physics.

I think you are confusing the Samsung fast charge port protocol which, after a data handshake, will raise the output voltage of the charger to 9V. This helps lower the current (and therefore the voltage drop across the cable) while actually increasing the delivered power. Only certain chargers are capable of delivering this, and only certain devices can take advantage of it.

5V * 2A = 10W
5V * 3A = 15W (USB 3.1 standard)
9V * 1.67A = 15W (Samsung fast charge)

There is even a USB-C PD spec that can deliver up to 20V @ 5A (100W!) after the device negotiates a "power delivery contract" with the charger.

Attached the standard 5V 2.4A Anker to my Samsung tablet, and the same tablet connected to a Samsung charger capable of their fast charge protocol.

PD is an example of a "Charging Port" where a device will request elevated charging power from the charger. If the Charger is equally equipped with a chip to negotiate the higher power, they will both switch.

The ports in the cars are -not- there as Charging Ports, they are there as Data Ports. And, as such, devices connected to them will operate at 5VDC only.

[turbo2ltr]

Originally Posted by ember1205

The ports in the cars are -not- there as Charging Ports, they are there as Data Ports. And, as such, devices connected to them will operate at 5VDC only.

All USB devices will charge using 5V. So i'm unclear what exactly you are differentiating when you call them "Charging ports" vs "Data ports" since literally EVERY USB DEVICE WILL CHARGE when plugged into it. The owners manually literally says "The iPod/iPhone charges while it is connected to the vehicle..."

I think we've crapped on this thread enough. We'll have to agree to disagree.

[ember1205]

Originally Posted by turbo2ltr

All USB devices will charge using 5V. So i'm unclear what exactly you are differentiating when you call them "Charging ports" vs "Data ports" since literally EVERY USB DEVICE WILL CHARGE when plugged into it. The owners manually literally says "The iPod/iPhone charges while it is connected to the vehicle..."

I think we've crapped on this thread enough. We'll have to agree to disagree.

It's less about the "capability" and more about how to ID a particular kind of port - Charging Ports are designed to be able to allow higher-speed charging than what the standard USB specs designate. They "start out" as a standard USB port but can change their operating characteristics if there is a successful negotiation between the connected device and the port. In order for higher voltages to be used for charging purposes, the charger (source), the device (sink), and the cable must all support communications to negotiate the increase in voltage.

Standard USB ports do not contain the electronics necessary to change to higher voltage outputs, so they are not Charging Ports per se even though they -will- provide power to the connected device in a manner that should facilitate charging of that device.