Laura Arjona Reina

Questions about USB chargers !lazypump

Laura Arjona Reina at

Ok, it seems that after some years, we are in a better situation about chargers: almost every portable electronic device can be charged by USB. Device connectors are not the same, but no problem, after several years of digital life, I have a bunch of different cables at home for almost any type of USB-ending :)

But every charger I see has different amperes. For example, here at home I have:

  • HTC charger, 5V/1A
  • Sony charger, 5V/850mA
  • Casio charger, 5V/650mA
  • ACME Corp. charger (do yo say that for the "unknown brands"? In Spanish we say ACME, or "NISU", "ni su madre lo conoce" ("even its mother doesn't know about it")), 5V/250mA
  • ACME Corp/NISU car charger, 5V/1A

So now: can all those chargers be used to charge any of the devices, I mean, are they totally interchangeable? Of course I always try to use the original one for each device, but that's not the case: chargers die and devices die too, and we try to reuse material.

I learn loong time ago about V = I * R the laws or electric current and so, but now, in real life....

  • would a charger with higher (or lower!) amperes than the original one damage my device?

  • Would I stay safe if I always use an 'equal or lower amperes' charger?

  • Do the different amperes affect the speed of charging the device?

  • Can I discard the cable factor? (they are more or less the same lenght, but some of them have a thicker cylindre near one of the ends, and others, not, only plain cable)

!lazypump

Andrew E likes this.

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As for amperage, the formula that helps me understand electric supplies is


power(in W)=V*I


which means that if volts are supposed to keep stable, a device demanding more current will only work (without overheating) with a source with enough power. The intensity a charger shows on the label is maximum intensity and that determines its power. I usually think about power as in "power to keep volts the same".

Paco Vila at 2014-07-21T10:29:44Z

testbeta likes this.

One of the best things the Evil (Google) provides is the charger of its tablets: 2 amps in a small device.

Manolo P. at 2014-07-21T11:30:54Z