Quote:
Originally Posted by barryem
With modern electonic devices with USB charging ports you can ignore voltage. The USB standard specifies 5 volts and every device expects 5 volts and every charger provides 5 volts, or very close to it.
Barry
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Not exacly true. Never safe to speak in ab
solutes except in rare circumstances. EVERY
CHARGER does not provide ONLY 5 volts or "very close to it" (unless you consider NINE VOLTS to be "very close to it"). Sure when POWERING devices in host mode, then there is a 5v standard. But some apple chargers intentionally charge at a higher voltage (which is HOW they can pump higher current into the device).
If you understand electricity or electronics, you know that POWER (especially waste power) = voltage divided by resistance. Small USB wires are relatively high resistance relative to charging current. Too much current and they get hot. So when they THINK (via those resistor values that vary between manufacturers) that it is safe to use more POWER to charge a device, they do that with an increased voltage (to deliver extra power without too much waste heat due to excessive current). For safety, the charging voltage is only increased while CHARGING in "fast charge" mode, after deciding that it is safe to do. Unfortunately, that variation in "standards" can cause confusion when mixing components from different vendors.
Anyway, speaking in absolutes is rarely a way to be correct, especially when technology is involved. Especially when you consider that most technology is created and maintained by technogeeks who tend to use precise and accurate language, and take words to mean exactly what they say.