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