Why do PD charging ports sometimes only support 65 watts and above devices (but not devices with less than 65 watts)?

Question

E.g., this laptop's specifications state (mirror) (MSI GS76 laptop):

PD charging port only supports 65W watts and above devices (e.g. adapter, powerbank).

I'd guess they expect that less beefy power supply won't keep up with charging the system under full load. They would rather not charge at all than slowly discharge the laptop despite it being plugged in (in certain conditions). — gronostaj, Jul 24 '22 at 05:43
@gronostaj thanks, why would they rather not charge at all than slowly discharge the laptop? Wouldn't slowly discharging make the battery last longer? — Franck Dernoncourt, Jul 24 '22 at 05:44
I'm just guessing here, but I think they don't want the laptop to behave in unexpected ways. Average user assumes that laptop plugged in = laptop charging. Realizing that battery is partially discharged or even empty after an intense gaming session is an unexpected surprise that are trying to avoid. — gronostaj, Jul 24 '22 at 05:50

score 1 · Answer 1 · answered Jul 24 '22 at 07:54

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USB Power Delivery (USB-PD) specifications have evolved over the years, and not all specifications are backward-compatible.

You may read about the different specifications in Wikipedia USB Power Delivery.

Below is the table that is found in this article, which can show the differences between specifications:

answered Jul 24 '22 at 07:54

harrymc

Thanks, interesting I don't see any threshold at 65 watts. – Franck Dernoncourt Jul 24 '22 at 08:07
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It's probably in the 60-100 segment. The port may be unreliable for less than 65W, or they wanted to play it safe. – harrymc Jul 24 '22 at 11:12

1 Answers1