AC Chargers - Watts? Volts? mAmps?

[odamizu]

Originally Posted by geekmaster

... Now, getting back to the ORIGINAL question in the first post, even if your charger tries to charge a battery too quickly, they have built in protection circuits to prevent a fire in your pocket, so it will generally not harm them other than shortening their life a bit. But still, better not to do that, just in case ...

This is why people like me (the OP) end up buying new chargers with almost every new device

[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.

Amps, on the other hand, shouldn't be ignored. If your device calls for 1.5 amps and you provide 1 amp it'll take longer to charge or even fail to charge if it's turrned on. If you provide more than 1.5 amps the device will only draw as much as it needs and no harm is done. So make sure you have enough amperage and you're fine.

With older devices not providing enough amperage could cause damage but devices made in the last few years are well protected against that.

So basically as long as they're USB devices just make sure whatever charger you use provides as much amperage as you need and don't worry about anything else.

I have a number of USB charged devices and one came with a 2.1 amp charger and I use that for nearly everything I own. Or I did till last year when I got a USB charger with 5 ports that plugs into the wall and provides 2.1 amps on 6 ports all at the same time. I think it cost about $25 or $30. I've used it on everything since I got it. I've never had any problems. Here's a link to it:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Barry

[geekmaster]

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

Not exacly true. Never safe to speak in absolutes 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.

[Cinisajoy]

Originally Posted by geekmaster

Not exacly true. Never safe to speak in abolutes except in rare circumstances. EVERY DEVICE 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.

This post explains why most of us said use the correct charger. Most of us do not want to take the chance on the OP ruining his device or worse.

[geekmaster]

Originally Posted by Cinisajoy

This post explains why most of us said use the correct charger. Most of us do not want to take the chance on the OP ruining his device or worse.

Mostly a problem with "quick chargers" (or chargers from apple, but ESPECIALLY cheap Chinese chargers that CLAIM to be for apples that are designed to charge at a higher voltage. There are teardowns that show some cheap USB car chargers that say "apple" on the package contain nothing more than a series resistor inside (hence supplying 12v when under a light load).

There are almost always exceptions and rare corner cases, as any good computer programmer ought to know well, making words like ALL and EVERY and ALWAYS and NEVER look pretty silly most of the time (at least to folks like me). Notice how I said "almost" there, for accuracy. Communicating literally is extremely important for computer programmers, because that is the only language computers know. Well, except for fuzzy logic and neural nets, but they are a whole different thing.

[barryem]

Originally Posted by geekmaster

=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.

I didn't mean to sound like I was speaking in abolutes. Someone asked for advice and I offered it, based on my own experience and the reading I've done on the topic over the years. I'm not an engineer and I don't pretend to be.

I've been following the advice I gave for lots of years. It's safe and reliable. I probably have 20 tablets at any given time and about 8 ereaders and a number of MP3 players, phones, portable media players, etc. I live in a retirement home where my neighbors have a lot more devices. They also follow this same advice. Their devices and mine tend to last for years.

Barry

[barryem]

Originally Posted by geekmaster

Notice how I said "almost" there, for accuracy. Communicating literally is extremely important for computer programmers, because that is the only language computers know. Well, except for fuzzy logic and neural nets, but they are a whole different thing.

I appreciate your use of the precise term "almost".

Barry

[geekmaster]

Originally Posted by barryem

I didn't mean to sound like I was speaking in abolutes. Someone asked for advice and I offered it, based on my own experience and the reading I've done on the topic over the years. I'm not an engineer and I don't pretend to be.

I've been following the advice I gave for lots of years. It's safe and reliable. I probably have 20 tablets at any given time and about 8 ereaders and a number of MP3 players, phones, portable media players, etc. I live in a retirement home where my neighbors have a lot more devices. They also follow this same advice. Their devices and mine tend to last for years.

Barry

I agree in the general case, if you are careful and avoid crap or fake (dollar store) chargers, it is almost always okay to mix and match chargers. However, when charging expensive devices (like my $700 cellphone), I am careful to use its own charger whenever possible.

However, when charging my kindles in batches of about 50, I even used USB hubs as power-splitters, and whatever else I could scrounge up, to recharge the batch.

My post was not just because you said "every charger provides 5 volts, or very close to it" after I had already explained dangerous exceptions to that case, but also because absolutes makes me raise an eyebrow so high it hurts.

[GreenMonkey]

Originally Posted by geekmaster

I agree in the general case, if you are careful and avoid crap or fake (dollar store) chargers, it is almost always okay to mix and match chargers. However, when charging expensive devices (like my $700 cellphone), I am careful to use its own charger whenever possible.

Unnecessary paranoia. And honestly the charger the company ships with the device might be worse than the one that comes with your iPhone or whatever.

Just don't plug it into a cheap P.O.S. charger from a dollar store gadget or whatever and you'll be fine. Power supplies have tolerance designed to deal with voltage a bit +/-. At worst, you'll get a 500ma charge which is a bit slow for tablets and other large-battery devices.

I think others explained it well but Extremetech has a good explanation page on this also.

http://www.extremetech.com/computing...our-smartphone

I really like this read for the more tech inclined/ interested. Engineering guy with a blog where he tears apart a bunch / tests them.

http://www.righto.com/2012/10/a-doze...-apple-is.html

Notice the worst are the counterfeit / knock-off chargers..very, very out of spec. Now those are the ones you want to avoid.

[Cinisajoy]

My two cents:
If you are unsure, use the charger the gadget came with. Or get a charger with the same specs.
A magnifying glass and good light can help you read the adapter.

[geekmaster]

Originally Posted by GreenMonkey

Notice the worst are the counterfeit / knock-off chargers..very, very out of spec. Now those are the ones you want to avoid.

But generally hard to spot without a side-by-side comparison with the "real thing" using a magnifier and a bright light. The biggest thing is to pay attention to details.