you wanna learn something bullshit about USB-powered devices, like fans and lights and such?
So, the latest video from Big Clive is on a little USB air pump, for backup aquarium ventilation purposes:

He tests how much current it's drawing, and it says 135 mA
He then tears it down, and discovers it's very simple: a motor and a resistor.
The resistor is not required for normal operation, and when removed, the pump now uses ~35mA

in other words, the resistor is 3/4ths of the current use of the whole device.
And why's it there? well, it does use about half a watt to just heat up the resistor, maybe the pump needs to stay warm to work?
NOPE!

It turns out that most big USB power banks are "intelligent" and automatically measure how much power is being used by each port. If that amount is too low, they turn that port off.
The idea is to not run the battery flat on small leakages for devices that are soft-off.

So if you have a fan that leaks a few milliamps when turned off because of a badly designed switch, it won't slowly kill your USB battery if you leave it plugged in for a month at the bottom of your purse. The power bank will turn it off.

but the problem is that some devices you might want to plug into a USB power bank don't need much power: simple flashlights, tiny fans, pumps like this...
They barely use any power, so some of the USB power banks won't consider them a Real Current and will turn them off

and when that happens, who does the customer blame? the USB powerbank? NOPE! they're like "huh, this stupid 10$ fan I just bought at the gas station doesn't even work for more than a couple seconds!" and throw it out.

so the people designing those devices solve the problem by adding a useless resistor across the power connectors, so that enough current will be used at all times, and it'll stay powered on.
And in this extreme case, it ends up using THREE TIMES AS MUCH POWER AS THE PUMP ITSELF

so let's say you go on amazon and grab this 5000 mAh power bank.
You want to run your pump off it. How long will it run?

so that's a 18.5 watt hour battery (5000 milliamp hours times the 3.7v of the battery).
It's using 0.675 watts (135 milliamps * 5 volts)

Divide that out, and you get 27.41 hours of battery life.

(ignoring that there'll be losses in conversion, so the real life is probably more like 18 hours)

but what if we are using a power bank with the same capacity but no auto-shutoff circuitry (many cheaper ones don't have it), and we mod the pump by removing that resistor?

well, now our power consumption is 0.175 watts.
So when we divide it out, we now get an ideal duration of 105.7 hours!

so now the device will last OVER FOUR DAYS simply because the USB power bank isn't trying to be "smart" and turn it off, and the device isn't trying to trick out the smartness by wasting power on heating up something that doesn't need heating up.

Sure, this is a small loss, and you probably never are going to run a little backup pump like this for that long.
But this device is just one of the ones that shows the problem the best, because it's so low-current otherwise.

it's just that because of multiple design decisions from different groups designing things for different reasons that we ended up in a weird world where the things that should be the most efficient have to intentionally be inefficient in order to satisfy customers