I Googled this and could never find a definitive answer, so I decided to try it out using the USB-C TurboPower 30 charger that came with my 1st gen Moto Z Force. The specs on the charger are 5V at (up to) 5.7A for a total of 28.5W (I don't believe the laptop pulls anywhere near this, just saying it's what the charger is rated for). The OEM charger (with barrel connector) is rated for 19.5V@2.31A, for a total of 45W.
Per the specs sheet, the battery is a 3-cell, 38WHr rated at 11.4V, giving us a total capacity of around 3300mA (3.3Ah) and an approximate charge time of 4 hours while the laptop is off (and assuming 0-100%). The USB-C port is USB 3.1 Gen 1 (aka regular ol' USB 3.0), which doesn't really tell us much, since the Power Delivery (USB-PD) spec is independent of the type-C connector (ie. having a type-C connector does not inherently mean it can accept power input for charging purposes). Since Dell doesn't advertise the USB-C port as supporting PD - and yet it does charge via the port - we can assume it at least meets the USB Type-C 1.2 spec of 5V@3A (15W). If it were true USB-PD, it would have to support a minimum of 20V and 3A (not necessarily at the same time, which is why 15V@3A and 20V@2A chargers are pretty common).
As for the actual test, the laptop did not appear to charge via USB-C when it was on. The white light on the front came on when the laptop was off and plugged in, however. Since I don't have a different USB-C charger to test it with, I don't know if that is a limitation dictated by the low output (eg. it could not successfully charge and operate at such a low wattage, so it never even tried) or one imposed by the hardware/firmware (eg. it doesn't officially support charging through the USB-C port, so all draw is disabled while the computer is on) or a combination of the two (eg. it only supports the type-C spec, not USB-PD, and so is therefore limited to 15W which isn't enough to both power and charge simultaneously).
It took right around 3 hours and 15 minutes to charge the laptop from 10% to 100%, so to make things clean, lets assume it was down by 3Ah (the amount we need to charge). I realize that Li-ion and LiPo battery chemistry is more complex than this, but let's also assume a continuous charge rate and overall efficiency of 90%. This gives us draw of around 1A by the laptop (using the formula: 3Ah / (0.9x) = 3.25 hours).
At this rate, it would take approximately 3.7 hours to charge the battery from 0-100%. This is in line with the specs sheet, which claims an approximate charge time of 4 hours (again, I'm assuming 0-100%). My knowledge of the engineering involved is minimal (and clearly oversimplistic), but I do wonder if this indicates that the charge controller is tied to both the barrel and USB-C ports. Clearly the laptop can charge while on using the OEM charger and barrel connector, so if the charge controller is the same, I'm wondering if a proper USB-PD charger (15V@3A or 20V@2A) would work, as well. It should be a relatively safe thing to check, as a PD charger would need to negotiate the charge rate and circuitry on both ends would have to agree. Failing that, it should do nothing.
Given the similarity of the 7373 to the XPS 9360, I would not be the least bit surprised to find out that the 7373 supports USB-PD charging via the USB-C port just like the 9360.
Not relevant to your laptop I general, but I also tested things with my Inspiron 15 7570. I first tried to use a standard 5V 1A USB-C phone charger and nothing registered. Then I pumped it up a notch by using the 45W USB-C charger of the Razer Stealth. Surprisingly my laptop actually registered it. However a warning popped up on screen telling me that the power source was 45W, and that it recommended me to use a 65W charger instead. Else the laptop would charge slowly. My battery icon on the taskbar actually showed the charging icon as well.
Hello to everybody,
I hope to be helpful giving this information. I have tested with full success the Aukey charger https://www.aukey.com/products/amp-usb-c-wall-charger-with-power-delivery-3-0-pa-y10.
This charger is recognized correctly from Inspiron 7373 and can charge without warning and in fast way.
Just wanted to point out that the Intel 7th generation processor version of this laptop (Inspiron 13 7378) is also able to charge via USB-C. I am using a Nekteck USB Type C Wall Charger with Power Delivery (PD) purchased from Amazon: https://www.amazon.com/dp/B0719KV9PH
I have updated the BIOS to the latest 1.25 version available before testing. Dell Diagnostics detects it as a 45W adapter. Pretty nice to have a charger that works with my Pixel 2 XL phone and laptop as well. 😃
The system BIOS is for multiply models could that mean all model should support charging via USB-C?
Dell Inspiron 7370/7570/7373/7573 System BIOS