Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/2.4

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BobH
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Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/2.4

Post by BobH »

Dunce Disclosure:
Until today, I was unaware that USB power supplies vary in amperage. I am ignorant when it comes to all matters dealing with electricity.

I just now learned some USB devices take their power in a less powerful current flow (1 amp) while others consume more powerful current (2.x amps) {Assuming I'm correct in stating current flow force is equivalent to power and is measured in amps.} This raises a question in my mind about what might happen if a device expecting 1.0 amps were to receive 2.x amps. Would the current fry it? Would the device be harmed in any way? Conversely, a device expecting 2.x amps would receive less than expected. I infer (SWAG) that the device would not be fried but that it might not receive enough power to make the device function properly.

Because USB is used to recharge batteries for so many devices today, the question of effects on recharge arises. My SWAG is that a more powerful current might not be compatible with batteries expecting less ('tho one would think circuit designers would have built-in fail safe function in their circuits) with negative consequences. Conversely feeding a 1.0 amp power supply into a battery expecting 2.x amps might cause no harm except possibly not fully recharging the battery or taking excessive recharge time. (Please refer to Dunce Disclosure above.)

If you know the answer to this, please share it with me. I've done a bit of searching but I lack enough basic understanding of electricity to separate wheat from chaff when reading things I found. Besides, I trust fellow loungers far more than I do unknown web pundits.

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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/

Post by viking33 »

The basic rule with device current draw is that a device will only draw as much amperage as it requires. Therefore it is safe to plug in a 1 amp unit into a 2 amp source, as an example. ( as long as the voltage is the same or very close ) A scenario of vice versa would probably not be a good idea, as one of both devices could be destroyed or seriously stressed. (tune for smoke!)

Those little power bricks are a good example. AC to DC or DC to DC is fine but the current is the key. People say, well, the plug and jack are the same so it should be OK. Not so!
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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/

Post by BobH »

Thanks, Bob!

I was hoping you would jump on this. What should one look for to determine if the device takes 1.0 amp or 2.+ amps? I purchased a new multi-outlet strip with surge protection that has 6, 110/120V AC, 2, 5V/21.4, and 4, 5V/1.0 USB Amp outlets. I plan to use the 5V/1.0 Amp outlets for charging devices unless I can find specs that say they can take 2.4 Amps at 5 Volts. For example, I cannot find data on my iPhone 6+ telling me how many amps the battery recharge function takes and at what voltage; so I'm going to do some searching to see if I can find out.

Also, thanks for confirming my recollection that amps measure current flow and indicate power consumed at a given voltage. (Right?)
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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/

Post by John Gray »

There is a fundamental difference between the maximum power which can be drawn from USB 2.0 (5V 0.5A) and USB 3.0 (5V 0.9A). "The charging downstream and dedicated charging ports provide up to 1.5A."

Some years ago, external USB hard drives of more than about 500GB used to use two USB 2.0 ports, because they drew more than 0.5A. More recent and more efficient hard drives have a reduced power consumption.
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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/

Post by StuartR »

If you plug a device that needs 2.4A into a 1A USB power supply then it will charge without any damage, but very slowly
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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/

Post by viking33 »

I agree with Stuart's post to some degree but personally, I would not knowingly do so. Higher current at the source is OK, lower, you roll the dice, particularly if the device is ON when you plug it into the charger.
A short dip into basic Ohms Law:

Charging power is based on three things: power (P, measured in Watts), current (I, measured in amps or milliamps), and voltage (V, measured in volts). The amount of power is determined by the equation P = IV. In other words, power is the product of current multiplied by voltage. Because larger devices like tablets have substantially bigger batteries than smartphones, chargers designed for the former tend to deliver energy at a higher rate (a higher current).

Going to the manufacturer for the exact specs is the best idea in your search for iphone6 + data.
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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/

Post by BobH »

My analogy for trying to remember terms that describe electricity's attributes is to consider it a fluid, as in a river or stream flowing, maybe past a dam. Potential is the unused power measured at a point. Potential is increased by a dam blocking flow/current. Current is the total pressure that the fluid stream applies. Power (watts) is what is produced by the water flow rate. It can be amplified by narrowing to increase flow rate or widening to reduce flow rate. For example, if water is channeled and dropped through turbines downstream and presumably the lower height at the bottom of the dam, power is increased. Without a dam and turbines to amplify power, it would otherwise be described by the flow rate of the current. The width of the stream is analogous to voltage which would be a constant at any point in time and has the attribute of amperage based on the width of the banks constraining the flow with greater constriction raising the amperage and widening the flow lowering the amperage. Less wide streams would have less voltage and wider streams more of it. The other attribute is how the friction of the water flow against the banks, bottom and air above is the resistance measured in Ohms.

I'm pretty sure these are gross over-simplifications if they are even remotely near a description for 6th grade science books. I have no clue what the mathematical relationships are among them and lack the skill to try to write them from my description.

Please feel free to poke fun at my lack of understanding of these basic principles about electricity, but I would greatly appreciate corrections and better analogies to use to remember them.
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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/

Post by BobH »

Follow Up:

I contacted Apple support to pose this question and explain the reason for asking. Even senior support advisors did not know the answer nor could they call it up immediately from their support system. The question was referred to their engineering staff (or so I was told). I received an email several days later saying that using anything other than 5V would damage the phone. Further it said that I could use the 5V/2.4A circuit to charge the phone even though the phone was designed to use with an adapter that uses 5V/1.0A whereas newer iPads use an adapter that uses 5V/2.xA AND that the more powerful adapter could be used with the iPhone without damage because the device has built-in circuitry to prevent problems (as I suspected) AND that using the higher amperage would allow the phone to charge more rapidly.

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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/

Post by ChrisGreaves »

viking33 wrote:
24 May 2017, 23:36
... a device will only draw as much amperage as it requires...
Hi Bob. This is counter-intuitive to me. When, like Bob, I think of fluid flow in a water pipe, I see the "device drawing power" as having a thin pipe that throttles/reduces the water that can enter the device. The manufacturer of the device can make that entry pipe as thin as they want, and so they can set an upper limit on the rate at which water/electrical power can enter the device. Hence, "it is safe to plug in a 1 amp unit into a 2 amp source". The unit with the narrow 1-amp pipe can take in water at only that rate, no matter how much water lies in the source/reservoir up stream.

But if I continue the analogy, a device with a 2-amp (or two-inch diameter) pipe connected to a source pipe that is only one inch would be somewhat starved of water, rather than being overwhelmed by water.
I can see that if my device were a washing machine with a 2-amp pipe, it would take twice as long (OK Pi times 2 times as long!) to fill as the manufacturer expected, but how would that damage the device. Perhaps a washing machine is not a good example; if the agitator starts after exactly one minute I would be agitating still-dry clothes. :scratch:

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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/

Post by ChrisGreaves »

StuartR wrote:
25 May 2017, 09:05
If you plug a device that needs 2.4A into a 1A USB power supply then it will charge without any damage, but very slowly
Hi Stuart. If I am still on track, your statement here is akin to my analogy of the washing machine - still filling up, but taking twice as long to fill as the manufacture expected it to take.

In my situation (live alone, retired etc) it makes little difference to me how long it takes my washing machine to fill as long as the clothes are ready to hang out first thing in the morning.
Likewise it makes little difference to me how long it takes my smart phone to charge as long as I can make phone calls first thing in the morning.

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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/2.4

Post by DaveA »

"it is safe to plug in a 1 amp unit into a 2 amp source"
I think you will find that the two have different plugs/sockets and should NOT be able to do this plugging in.

Electricity and water are two different methods of flow but are some what similar.
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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/2.4

Post by StuartR »

It's fine to plug a USB device that only consumes 1amp into a USB socket that can provide 2amp. It will only draw the current it needs.
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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/2.4

Post by PaulB »

And then, in the Apple World, it gets complicated.
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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/2.4

Post by ChrisGreaves »

DaveA wrote:
17 Dec 2020, 15:55
I think you will find that the two have different plugs/sockets and should NOT be able to do this plugging in.
Hi Dave.
When you speak of different plus/sockets here, are you speaking of the cylindrical pin plus, typically with a bright yellow interior which i see among my various power bricks for laptops? I have seen web pages with some five or six different-diameter plugs.
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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/2.4

Post by ChrisGreaves »

PaulB wrote:
17 Dec 2020, 22:35
And then, in the Apple World, it gets complicated.
Thanks for this link, Paul.
It is especially appropriate for the table towards the end.
I am in the process of cataloguing all my various chargers/power bricks etc and building such a table.
I have come across one unit that stated only the Watts, and left it to me to determine the voltage.
Too I realized that a proper current/voltage/wattage description (table) should include figures for the input as well as the output.
I have found one unit that states "110-240v" on an adhesive label on one side of the unit, and a second, smaller label "120v" on the other side; easy to miss!
I suppose that the second label is affixed for North American shipments.

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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/2.4

Post by Leif »

ChrisGreaves wrote:
22 Dec 2020, 12:28
I have come across one unit that stated only the Watts, and left it to me to determine the voltage.
This could be because it doesn't have a regulated output voltage, and so the output can only be accurately rated as a value in Watts

ChrisGreaves wrote:
22 Dec 2020, 12:28
I have found one unit that states "110-240v" on an adhesive label on one side of the unit, and a second, smaller label "120v" on the other side; easy to miss!
I suppose that the second label is affixed for North American shipments.
Many modern switch-mode chargers will happily work with any AC voltage between 90 and 240VAC. This means they can be used in many countries, simplifying manufacturing and reducing costs.
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Re: Some USB Devices Use 5V/1.0 Amp Power and Others Use 5V/2.4

Post by DaveA »

ChrisGreaves wrote:
22 Dec 2020, 12:24
When you speak of different plus/sockets here, are you speaking of the cylindrical pin plus, typically with a bright yellow interior which i see among my various power bricks for laptops? I have seen web pages with some five or six different-diameter plugs.
Yes, the diameter and/or color is different for different power usages.
Also the device USB plugs (the end that is inserted in the tablet, phone and etc) are different for different functions including power.
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