USB charger manufacturers are bad at math

I was on a lookout for USB charger that has 4 ports and doesn’t have any serious limits per port like most cheap chargers that drop to 1A output when more devices are connected. So I found few of them that claimed they have 4x USB each with 2.4A output which seems to be the maximum for regular USB chargers that don’t use specific quick charge techniques. Perfect. I’ve checked one from BASEUS, a Chinese maker that I generally have really good experience with. Their Qi charger is pretty good. Then I’ve noticed in reviews people were complaining it’s not reaching specified outputs. So it made me wonder what’s the deal. And then I’ve noticed a basic math problem.

The given USB charger has 4x USB, each is suppose to deliver 2.4A of current. At 5V, that makes each port output 12W of power. Which is odd because the specs say adapter has maximum total output of 40W. That’s 10W per output at only 2A.

It’s similar with RAVPower’s 4 port charger I looked up on Amazon and sold by RAVPower itself. They state up to 2.4A per port, but total output is 40W and 8A. Meaning max per port output is only 2A.

Only one that doesn’t really say specifics is ANKER which only states up to 40W output on 4 ports so I can only assume it’s 2A per port.

Turns out finding a charger that actually does 2.4A on every of 4 ports no matter the load is really hard. They are all some variations of 36W and 40W total wattage, but it has to be 48W to output that kind of power.

1 thought on “USB charger manufacturers are bad at math

  1. Thats not an issue with their math, but just how power supplies in general work. It’s the same deal with ATX PSUs using multiple 12V rails. If you add them all up, you’ll get a bigger number than whats the total rating for particular voltage.
    Just a internal design, same deal with usb charger. That still doesn’t mean it wont’t charge 2.4A per port.

    Like

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