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XPS 15 9570, loading power bank from USB Type-C PD at high rates
Hi,
as XPS 15 9570 can be loaded via USB-C using power bank at high rates eg. 45/60W, I have a question about using it for doing the opposite. If I have a power bank that can be loaded at rates 45/60W, could I connect it to a laptop that would be connected to a power source and have the power flow that way? Maybe you have some link to full specs of these ports as those which I found don't provide this sort of information.
TL;DR input on USB-C PD is 60W from what I know, yet what is the output?
Background: I would rather like to have just one power supply with me - the dell's 130W - and then whenever I am connected to the power supply I would like to charge the laptop as well as a power bank. Of course, there is a power bank that can be loaded using the typical dell charges, yet I think that USB-C is a better choice for the future.
DavidDavidDavid
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September 11th, 2019 04:00
I was thinking about maybe using some bothways USB-C powerbank, eg there is Xiaomi 3 PRO with USB-C 5V/3A ,9V/3A, 12V/3A, 15V/3A, 20V/2A (45W max) rather than Dell power companion that has output 1 x power DC jack - 19.5 V - 2.3 A 65W and dell cahrger input, as Xiaomi claims that it can use 45W both ways, yet I found that:
The Xiaomi Mi Power Bank 3 can charge in just 4.5 hours if you have a 45W charger. - https://www.xda-developers.com/xiaomis-20000mah-mi-power-bank-3-charges-devices-45w-usb-c-30/
But 45W * 4.5h = 202.5 Wh while the powerbank is 74Wh... that would mean that it actually takes just ~16.5W
That lead me to search for stats for Dell power companion
I was able to find that:
It takes approximately 3 hours to fully charge the power
companion. - http://www.manualsdir.com/manuals/623059/dell-portable-power-companion-12000mah-pw7015m.html?page=8
Funny enough that manual is for both 45Wh & 65Wh versions and while for the 45Wh dell powerbank that would mean it takes only 15W input, for 65Wh it is ~22W input.
To wrap things I was able to find:
4 Thunderbolt 3 (USB 3.1 Gen 2 Type-C) port with Power deliverySupports USB 3.1 Gen 2, DisplayPort 1.2, Thunderbolt 3 and also enables you to connect to an external display using a display adapter. Provides data transfer rates up to 10 Gbps for USB 3.1 Gen 2 and up to 40 Gbps for Thunderbolt 3. Supports Power Delivery that enables two-way power supply between devices. Provides up to 5V/3A power output that enables faster charging - https://topics-cdn.dell.com/pdf/xps-15-9570-laptop_specifications_en-us.pdf
5V * 3A = 15W, which is the answer to the question.
Coming back to previous site:
The Xiaomi Mi Power Bank 3 can charge in just 4.5 hours if you have a 45W charger. Using a regular 5V/2A charger will take about 11 hours to charge, while an 18W charger will take 6.5 hours. - https://www.xda-developers.com/xiaomis-20000mah-mi-power-bank-3-charges-devices-45w-usb-c-30/
Which leads me to conclusion that all powerbanks require way more power then they are using to charge at any reasonable time.
samos1111
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September 5th, 2019 06:00
The XPS 15 can feed other devices via USB-C, but I'm not sure how much power and if more than 5V. I recall in BIOS there is a setting whether you want to allow this while the laptop is off.
There's a Dell 130W USB-C PD charger that probably does the trick, but it is probably cheaper to get a separate 60W charger for the powerbank.
For travelling light, the XPS 15 can even survive runing on (most) USB-C PD 60W@20V chargers, but in a heavily throttled-down power profile.
jphughan
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September 5th, 2019 07:00
@DavidDavidDavid some Dell laptops have a BIOS setting that allows you to customize the USB PD output level. Typically the options are 7.5W or 15W. The fact that a system can accept a certain wattage level to charge itself does not mean it can provide that same level. Keep in mind that if you're trying to use the system, the system's "power budget" design needs to consider the amount of power required to run the system itself, which will of course limit power output options from its peripheral ports. I suppose in theory you could have a system that allowed high wattage output while the system was asleep or powered off, but I haven't seen that implemented on laptops.
Also, the 9570 may have changed things, but last I checked, the XPS 15 will not use a 45W power source; it requires a minimum of 60W. I believe it also requires a power source that supports 20V output. But even if you decide to use that type of power source, keep in mind that it's providing less than half the wattage level the system is designed for, so although that might be fine for charging the system while it's asleep, if you try to actually use the system while it's connected to a 60W source, it will likely throttle CPU and GPU performance to try to operate within the reduced power budget. As a last resort, it might continue draining the battery even while connected to that power source in order to make up the power shortfall, but it won't do this just to maintain optimal performance because that situation of course means that your system will eventually die even while connected to power.
jphughan
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September 5th, 2019 07:00
In addition to my earlier reply, if you can't find a BIOS option to set USB PD output, then unfortunately PD output specs are seldom published on laptops. However, one way you might be able to figure it out would be to use a USB-C multi-meter like this one. I own that one, and I like it because it's inexpensive, easy to use, and kind of fun to experiment with. I also have a similar one for USB-A ports.
DavidDavidDavid
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September 9th, 2019 13:00
Can you provide any source for that requirement of 60W@20V?
samos1111
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September 9th, 2019 14:00
Actually I think the minimum is 45W@20V, but most such 3rd-parties don't work. While at 60W@20V most were found to work, although USB PD debugging tools have shown unreliable PD negotiation.