OP mentioned a 600W charger. Sure there’s no danger in plugging into a USB port but 600W of USB ports would look dumb and are probably not what I’l OP is referring to when they mention “DC plugs” on their “emergency power supply”. They also mentioned a box fan in the comments.
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 a vague 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 and have a chance of giving you a 0.2% efficiency gain on the whole system. But don’t try and run a large box fan on them.
OP mentioned a 600W charger. Sure there’s no danger in plugging into a USB port but 600W of USB ports would look dumb and are probably not what I’l OP is referring to when they mention “DC plugs” on their “emergency power supply”. They also mentioned a box fan in the comments.
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 a vague 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 and have a chance of giving you a 0.2% efficiency gain on the whole system. But don’t try and run a large box fan on them.