The “charger bricks” for some of your electronics convert AC to DC for you, but trying to bypass them “for efficiency” has a high probability of ending poorly.
Like plugging your charging cable into a USB port instead of a wall outlet? There’s no danger there.
There is still a charger brick there…now cut a USB cable plug off and connect the power wires in to a wall outlet directly…
Plugging into a USB port on your computer? Your power supply is already converting 120/240 vac(depending on location) to 12 vdc. That’s fine. Bypass that power supply and connect your phone to wall power directly and expect flames…
USB’s 5 volts, ain’t it? Not 12. Feed it 12 and you’ll break stuff.
(At least without USB-C PD negotiation.)
– Frost
Oh shit you’re right. I shouldn’t respond with a technical answer late at night…
Ludicrous0251@piefed.zip 1 week ago
OP mentioned a 600W charger. Sure there’s no danger in plugging into a USB port but 600W of USB ports would look dumb. They also mentioned a box fan.
USB ports are fine for USB things and those provided by the charger may be slightly more efficient than using one of the AC plugs and a separate phone charger but were taking marginal gains on a tiny load that runs for a small amount of time. On a large AC battery system, the USB ports are just as likely to use an off-the-shelf AC/DC converter like most chargers as they are to use a DC/DC converter built for their operating voltage. They’re also limited in power output to whatever the battery manufacturer decided, which is probably not a lot.
A hypothetical person with infinite time, knowledge, and money, could create a whole DC ecosystem yes, but someone like OP posting for an ELI5 on the difference between AC and DC needs an AC system 99.99997% of the time. If it comes with extra USB ports, whatever, they’re fine I guess. But don’t try and run a large box fan on them.