Overthinking USB charging

iljitsch · 2026-04-08T15:15:36+00:00

I don't like perpetual threads, but this one may become a long-lived one. Please add as appropriate. In the past year, I got both a 100 W USB-C PD charger and a big USB-C power bank that can also deliver 100 W. The charger has four USB-C ports and one USB-A, the power bank two USB-C (one of which may be used to charge the power bank rather than discharge) and one USB-A. The interesting thing here is that these need to distribute the available 100 W over the ports in use. Which requires a notion of "in use". As the charger is hidden behind the couch and thus doesn't allow for easy plugging/unplugging USB-C cables, I like to have cables connected and then simply plug them into devices to charge them. For USB-C cables/devices this works great, as when those are not plugged in, they are ignored for the purpose of distributing power. This is not true for cables plugging into the USB-C ports but having a ~ USB-A destination. Here, just having the cable plugged it registers as in use, so they get their portion of the power, even if nothing plugged in. This also applies to the Apple USB-C to MagSafe 3 cable included with my recently acquired MacBook Air. This is otherwise a completely perfect innovation, giving me the USB-C PD benefits but also the MagSafe benefits. My last computer before MagSafe was a PowerBook which was once flung across a room as someone stepped on the power cable. My first computer after MagSafe was a 2016 MacBook Pro with only USB-C ports where a USB-C cable was destroyed (but fortunately no damage to the computer) after someone stepped on the power cable. The Apple power cable is also thinner than equivalently rated USB-C power cables and of course doesn't take up a 40 Gbps port for just delivering power. But there's also tons of stuff that only takes single digit Watts to charge. Like AirPods or other headphones. Or aTV remotes. Plugging those into a high capacity charger removes up to 60 W from the other ports, so that's pretty bad. But... what if you still have an old school USB-A multiport charger? I found one of those back in a closet not too long ago and it's now working nicely in my bedroom with an Apple lightning cable that can deliver 5 V 12 W as well as my Apple Watch magnetic connector and a 5 W iQ charger. With USB-A there are different rules for what counts as "in use" and a 60 W 5-port charger has fewer issues distributing the power. So this type of charger is really useful in certain circumstances. What makes everything more complex is that I'm on a dynamic electricity pricing contract, where electricity prices are often very low during the afternoon when there is a lot of sun. When that happens, you want to charge power hungry devices quickly to take advantage. Slow charging stuff is then less interesting. So: make sure your big USB-C PD chargers can do their thing quickly, and have slow-charging stuff on more modest USB-A multiport chargers.

Thread starter iljitsch
Start date Apr 8, 2026

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continuum

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Apr 8, 2026

Apr 8, 2026

Paladin said:
Generally, the better models tell you how each port works under which conditions.

++;

But yeah, as said, doesn't hurt to verify. I find you can generally trust UGreen, Anker, Aukey, etc... aka the major brands.

Smaller brands are a different story. Been burned a few times, usually by random brands on Temu or Amazon or whatever that had good reviews-- one dual port USB-C car charger I picked up claimed 90W total, 45W + 45W each port... yeah no, neither port could deliver even 45W. -_-

Last edited: Apr 8, 2026

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