Quote:
Originally Posted by DNSB
No argument there. But I thought a warning that mixing and matching devices and chargers can be a Very Bad Idea was in order.
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Yes, it is. Even when it's not "fatal" to the gadget, I find that I have multiple 2A 5V USB chargers, but some gadgets will only charge at more than 0.1A or 0.5A at their full 1A or 1.5A on a particular charger. None of my generic 2A chargers work any gadget at more than 0.5A.
The reason?
With true USB-C and USB 3.x at both ends there is negotiation of voltage and current via serial data. But if the charger is using USB 1.x to USB 2.x and just the four wires of USB-A (or a USB-C wired like USB-A), or the gadget with USB-C socket only uses the micro/mini/USB-B 1.x to 2.x wires, then the USB data pins D+ and D- have either fixed resistors or fixed voltages. The gadget (ereader, phone, tablet, mp3 player, camera) then measures those which indicate the maximum current the charger can supply. Unfortunately there are maybe three incompatible standards for what the measurement means. If the gadget can be sense of it then it will charge at only 0.1A or 0.5A, rather than 1A or 1.5A. The charger never "pushes" extra power on the 5V system. The state of the D+ and D- pins merely indicate the available current (power = current x volts). It's even possible for a badly designed 5V charger that can only do 1A or even 0.5A to look like a 2A charger, then something that takes 1.5A will eventually cause the charger to fail.
The idea of only supplying a cable and making chargers separate to reduce costs and waste is good. Unfortunately there are many clueless makers of gadgets or chargers.
So DNSB is 100%, the best idea is using the "official" charger, or one that works for same make of gadget with same current marked on it. The available charger current at 5V should equal or exceed the current marked on the 5V gadget, though as explained above the gadget may charge slower than it should.
If you have a 500 W 5V PC PSU and wired it to USB +5V and 0V and connected the correct voltages/resistances on D+ and D- wires, then the 1.5A max charging ereader will still only take 7.5W maximum. If the D+ and D- connections don't seem to suggest a 2A PSU, then the ereader or other gadget will use either 0.1A or 0.5A, that's 0.5W or 2.5W. Even if it's a 500W or even a 1000W power supply.
Similarly if you have a PC mother board and graphics that only takes 180W max via an ATX connector, a 1000W ATX PSU will not hurt it, and likely less than 180W is used.
In most of Europe the main board of the house can at a minimum do about 15000W (or maybe 20000W). A continental socket is 16A max (3520W), but a kitchen radio or USB charger may take less than 10W. UK/Ireland and some other places use a 13A plug which allows 3120W in the UK (240V), but other places use 230V or 220V. The actual power taken is depending on what's plugged in. I have a 5W mains LED lamp on a 13A 230V socket (about 3000W), though Ireland pretends it's European 220V (Makes no difference to most things). So it's using 5W. If you plugged in heaters and kettles and toasters on all sockets and put oven, grill, rings, microwave, dryer, shower, water heater, washing machine all on at once likely trips or even main fuse would go on your distribution board.
The USA has 110V (approximately) sockets, but the house will also have 220V for wired in appliances. The sockets using flat blades are 15A, so a nominal maximum of 1650W. No fast boil 3000W plug in kettles like in 220V to 240V outlet countries. Hence in USA a dryer or washing machine is usually wired into the 220V.