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October 8th, 2020 14:00
Precision 7520, TB16 dock, undersized power adapter warning
Much like a handful of others in this community, I too have a question about the "undersized power adapter" warning. My situation -- TB16 connected to Precision 7520. Currently use the old school ePort II replicators, but the TB16 and TB19 (preferably) are cleaner/nicer. So, what's truly the big deal with using an undersized adapter (240w) through a TB dock (max 130w)? I'm not questioning why/not, I'm just curious if there are known repercussions in doing so (without also connecting supplemental power along with the TB connector. In the end, if all this means is it takes longer to charge the battery, that's no big thing -- I tend to run the system connected more than disconnected (in terms of power) anyway. Lastly, I'm not looking for "guesses" or "assumptions" -- hoping someone here has true/real experience in doing this (and is alive to tell me, and others, about it). :0)
DELL-Cares
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October 9th, 2020 05:00
Thank you! We have received the required details. We will work towards a resolution. You may receive assistance or suggestions from the community members as well.
Dell would not know the "known repercussions" because we do not support or test using undersized power adapters. A guess would be that this would result in the battery taking a longer time to charge and you will experience performance drops on the system.
The recommendation is to use the 240W AC power adapter for the TB16 dock when used with any of the Precision Mobile Workstation laptops. In addition, the Precision 7510/7520/7710/7720 require AC power adapters be connected to BOTH the laptops and the TB16 dock.
hcna_its
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October 14th, 2020 07:00
For clarification purposes (for anyone considering the same):
A) I am using a 240W AC adapter with the TB16 dock. It is the dock/technology that is limiting anything more than 130W through the Thunderbolt connector (hence the "warning" of an undersized adapter).
B) Against Dell's requirement, I am operating a 7520 without the "extra" power adapter connected directly to the laptop and am not seeing/experiencing any obvious performance-related issues other than the battery taking longer to charge (it is, in fact, charging).
C) Connected to the dock includes dual Dell U2719H displays (via daisy-chained DP cables), one display with integrated USB hub connected, one external 3.5" HDD, wireless mouse/keyboard set, sound system (speakers/sub), UPS and wireless smartphone charging cradle...all of which work, without issue(s).
jphughan
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October 14th, 2020 08:00
@hcna_its The TB16 is limited to 130W over USB-C/TB3, which is already above the 100W max of the official USB PD spec. Dell did something to stretch that to 130W to support systems like the XPS 15 and Precision 5500 series, but there's a limit to how much power can safely be carried over that cable. As you found, Dell's guidance for these earlier Precision 7000 Series systems is to keep the AC adapter connected separately, otherwise in addition to slower battery charging you may see throttled CPU and/or GPU performance, especially in workloads that use both heavily. To address this, Dell later created the TB18DC, which has since been replaced by the WD19DC. Those docks connect to TWO ports on the system and can therefore supply up to 210W, without needing a separate AC adapter. But the 7520 doesn't have two USB-C/TB3 ports and thus can't use those docks in that mode. I guess that didn't arrive until the 7x30 models.