OK, I'm loving having a laptop with USB C power supply. Most power banks won't *charge it*, at least not with power on, but they will run it in "not charging" state very well, with basically no drain on internal battery.
@dalias they do alright. But they won't charge a laptop that shutdown due to a fully drained battery. (He says, after a recent power outage...) The machine needs enough juice to negotiate with the USB-PD charger before the charger will send any power.
@hyc But then how does the AC adapter work when it also needs to negotiate USB-PD?
@dalias maybe it has a default fallback? I had to dig up my OEM charger to bring the thing back to life. (Lenovo Legion7). That has its own plug, separate from the USB PD port.
@hyc I would think it could charge, albeit very slowly, from the unnegotiated 5V present on the USB power lines, then switch once it has enough power to negotiate. As long as the charging circuit is capable of accepting 5V and boosting it to cell pack level.
@dalias hmmm, maybe. Well, my USB charger has a display for each output and it was showing zero, so I don't think waiting for a slow charge would've made any difference.
@hyc Some chargers (especially power banks) don't provide an unnegotiated 5V charge to avoid draining while idle. I don't know exactly how they work, but if you plug in a device that wants that (like some cheap toys), it'll only charge for a few seconds, then turn off.
@hyc A hack to get some of these to work is to plug something else into one of the other output ports. If they're single-output-voltage, having both plugged in will force everything to 5V, and the device that negotiated it will keep the other port live and charging.
@dalias yep. I've gone thru the aggravation of searching for dumb power banks. I wanted to power a motion sensing LED strip, but when the strip was idle the power banks would turn off. So annoying. Even some of the assemble-yourself power banks do that too.
@hyc In fact I've noticed various devices seem to behave this way when fully drained: taking hours to charge up enough to show that anything is happening. And I assume this is from just accepting the baseline low-current 5V USB because they're unable to power up enough to negotiate. Which seem stupid since they could let the negotiating circuit run off the 5V pulling <10mA.