this post was submitted on 20 Jul 2024
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My laptop charges with USB C, so when the standard charger broke, I just used the USB out port from an EcoFlow battery. The display on the battery said the laptop pulled 25-30 watts while charging. So, why can't I use just any USB brick that can output more than 30 watts?

Is there something that is bound to go wrong that I don't know about?

Are laptop chargers really that special?

(Edited for clarity)

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[โ€“] [email protected] 3 points 3 months ago (1 children)

The OEM brick is rated for 65 watts, does that change things?

[โ€“] [email protected] 2 points 3 months ago

Yeah, you should be better off with more random stuff. I have taken apart several dozen power supplies like these for various projects in the past. The ones with power factor correction start as low as 80 watts, but don't become common until around 120 watts. In my experience, the supplies with power factor correction tend to also have a smoother output with far less noise overall. The lower power stuff can be like the wild west. Connect up some Arduino project and power supply noise can make you chase your tail.

The same basic thing applies here. The laptop was likely designed for a specific type of filtering on the supply side. There are always margins, and battery managing chips have gotten a good bit more sophisticated, but in the end doing outlier things to a circuit that was designed to a price is always an iffy proposition. The PD circuit is a known input randomness factor for the laptop engineers, but ultimately the engineered reliability factor of the OEM supply is going to have slightly more potential quality than some contract developed and contract manufactured venture capital driven USB-C PD power supply where a fraction of a penny is an absolute warzone.