Can some devices be powered directly from a wall outlet?

[Masutin]

Usually, small devices use only battery power. Are there any multimedia devices (not only readers), smaller than a netbook, that can get power directly from the mains, i.e. are equipped not only with a charging circuit but a mains power circuit as well?

[Quexos]

Originally Posted by Masutin

Usually, small devices use only battery power. Are there any multimedia devices (not only readers), smaller than a netbook, that can get power directly from the mains, i.e. are equipped not only with a charging circuit but a mains power circuit as well?

If you mean simply being connected to a wall outlet to charge then an ipad can do that. If you mean connected to a wall outlet as a main source of power for use, I don't see the point of having a portable device that you can only use when plugged to a wall outlet.

[Abtacha]

Most devices should be usable while they're connected to the charger, as for e-readers I know the Kobos can be. I haven't used any other current readers but I would guess they work while connected to the charger as well.

[dwig]

Originally Posted by Masutin

Usually, small devices use only battery power. Are there any multimedia devices (not only readers), smaller than a netbook, that can get power directly from the mains, i.e. are equipped not only with a charging circuit but a mains power circuit as well?

I'm not aware of any small portable devices that contain their own "mains" power circuit. The necessary size of the circuitry and the bulk of the required cord connector make this approach a non-starter.

You'll find that all existing tablets and ereaders use an external "brick" of some sort to provide the "mains" to low voltage DC conversion. Most (all?) will operate fine while plugged in to their AC adapters. The Kindles I've encountered all do as does my Dell Venue 8 Pro tablet (Win8.1). Even my old Sony Clie devices would work fine while charging.

[fjtorres]

All you need is a long enough USB cable since most readers and tablets charge via USB.
Alternately, you could use an ordinary extension cord between the mains and the power adapter.
Both options should cost about the same.

[theducks]

I am going to take your 'Mains Power' question Literally.

So the answer is none to very few.

My 1995 Toshiba CS series was the last Laptop I had that had a '100-240V' connection.

Mains voltages invoke an additional level of regulatory compliance. (CSA, UL, VDE...), that is why all those power bricks/wall worts are popular (besides the weight/space saving). The regulations pause at the low voltage connection.

USB (5V) chargers became more popular because of Electronic Waste reduction rules, by eliminating the need for proprietary chargers for common use items. (So why do many keep shipping chargers . IMHO Kindle did it right. If you need a charger, buy the charger, otherwise just use the cord

Of all my devices, only my Garmin Nuvi will not function (as a GPS) normally with a USB cable connected to power.

[Masutin]

Thank you all for thoughts!
To clarify, I was wondering about a device that can alternate between DC power (via AC adaptor or USB) and battery power, as in laptops or netbooks?
Even simple phones work while being charged, but I presume the power goes through the battery still, as probably there is no other way. True, portable devices are not meant to be plugged in permanenty. But for uses near a fixed power supply, again laptops and netbooks aside, I envisage a unit with an e-ink or a color screen that uses the battery only as required.

[fjtorres]

Originally Posted by Masutin

Thank you all for thoughts!
To clarify, I was wondering about a device that can alternate between DC power (via AC adaptor or USB) and battery power, as in laptops or netbooks?
Even simple phones work while being charged, but I presume the power goes through the battery still, as probably there is no other way. True, portable devices are not meant to be plugged in permanenty. But for uses near a fixed power supply, again laptops and netbooks aside, I envisage a unit with an e-ink or a color screen that uses the battery only as required.

Well, I don't think you'll find many devices with replaceable rechargeable batteries these days but if you find one and take out the battery and then plug in the external power cable it might work.

It *does* work with the XBOX One wireless controllers: they take disposable or rechargeable batteries, a proprietary LithiumIon battery or... nothing. The controller charges the proprietary battery via a generic USB to micro USB cable and it works just fine as a wired controller with a long enough USB cable.

Other devices may or not work that way but since so few come with user replaceable batteries because thin is in it would have to be an older model most likely.

[cromag]

Originally Posted by Masutin

Thank you all for thoughts!
To clarify, I was wondering about a device that can alternate between DC power (via AC adaptor or USB) and battery power, as in laptops or netbooks?
Even simple phones work while being charged, but I presume the power goes through the battery still, as probably there is no other way. True, portable devices are not meant to be plugged in permanenty. But for uses near a fixed power supply, again laptops and netbooks aside, I envisage a unit with an e-ink or a color screen that uses the battery only as required.

I have several "generic brand" Android tablets, ranging from a 4.3 inch to a 10.1 inch screen. All of them will continue to run while being charged from a wall charger.

[pidgeon92]

Originally Posted by cromag

I have several "generic brand" Android tablets, ranging from a 4.3 inch to a 10.1 inch screen. All of them will continue to run while being charged from a wall charger.

Yes, but they probably cannot bypass the battery. That is, if the battery is completely flat, it will need to come to a minimum level of charge before the device will boot.

[crich70]

My Kindle Fire can be used while charging though of course as the cable is rather short I am limited on how far I can go from the outlet at that time.

[TechniSol]

OP,

I've read this whole thread, twice in fact, and the only thing I've come away with is that you very likely have some mistaken notion regarding how most portable electronic devices work and are designed... Honestly, reading both your posts I'm still unsure what you're really trying to ascertain.

A battery only device typically uses only replaceable one time use or rechargeable batteries, and may or may not have a charging circuit. If so, the charging circuit may not provide enough current to run the device without leaching power from the batteries as well. Less likely in modern designs, but possible.

Most modern devices with rechargeable batteries have AC(you'd say mains) or DC adaptors supplying sufficient current to run the device as well as charge the batteries -though it is far from unheard of that operating the device while charging leads to slower charging of the batteries... You may notice that some manufacturers will offer a lower current adaptor or power supply with a laptop that isn't capable of powering the device and charging quickey, or at all, but also offer a higher current or wattage unit capable of higher performance. Sometimes, it is felt that the lesser adaptor is preferred for portability as they are usually physically smaller and that having enough current to power the device for operation is more than sufficient.

It really comes down to how much current can be supplied to the device via the adaptor and how much current the device requires to operate. The surplus is available for charging, though may not be fully utilized as batteries can only be charged at certain rates based on their design and construction or overheating and rupture or explosion might occur due to gas overpressure or the like.

Personally, I tend to prefer adaptors sized to be able to power a device as needed while being able to charge the batteries at a reasonable rate. However, it is fair to note that everyone's idea of reasonable varies somewhat based on usage patterns, cost, and trying to pack and transport adaptors and other possibly needed peripherals, etc.

I'm a big fan of the current trend towards "nearly universal" acceptance of 5Vdc micro-USB adaptors for cell phones, tablets, and similar devices. I wish notebooks and laptops would join the movement, but laptop batteries tend to be of such high wattage that it would take quite a while to charge them even with a 5Vdc @ 2A charger. That's only a maximum of 10 watts per hour... My old Lenovo X200 laptop/tablet has a battery rated 14.8Vdc@5.2A that's nearly 80Watts! Assuming lossless conversion (80 to 95% is far more realistic) it'd take 8 full hours just to charge the battery with the laptop powered off.(more like 10 hours, or more, with typical losses.)

The other downside for designers and engineers is that higher currents require larger conductors, wider, heavier traces on pc boards, etc., so it seems somewhat unlikely that higher current, lower voltage batteries will become popular soon for higher wattage requirements. It's a shame though, as being able to use the same adaptor for everything would be pretty convenient and very handy in a pinch. As it is, I shall continue to be pleased just to have that ability with my tablet, e-ink reader, and cell phone.

[fjtorres]

Originally Posted by TechniSol

I'm a big fan of the current trend towards "nearly universal" acceptance of 5Vdc micro-USB adaptors for cell phones, tablets, and similar devices. I wish notebooks and laptops would join the movement,

.

That is on the horizon.
On the one hand we already have the Intel stick computers that run off USB power...
...and on the other we have the next USB spec, seen in demoware at CES that can provide higher power through the new connector.

The big issue is going to be the display but ultra-low power LCD and OLED displays are being worked on.

Add them together and USB will be able to power a lot more devices, including (low end) laptops. With Intel continuing to drive down the power requirement of its mobile CPUs it will soon be doable with Core CPUs as well as the Atoms. Figure 3-5 years for the Core line.

[davidfor]

Originally Posted by Masutin

Thank you all for thoughts!
To clarify, I was wondering about a device that can alternate between DC power (via AC adaptor or USB) and battery power, as in laptops or netbooks?
Even simple phones work while being charged, but I presume the power goes through the battery still, as probably there is no other way. True, portable devices are not meant to be plugged in permanenty. But for uses near a fixed power supply, again laptops and netbooks aside, I envisage a unit with an e-ink or a color screen that uses the battery only as required.

No, you have it wrong. All devices with rechargeable Li-Ion batteries will not use the battery at all when they are plugged in. They will be running off the power while charging the battery. Once the battery is fully charged, the charging circuit will be turned off and the battery will sit idle until you unplug the device. This is done to prevent damage to the battery. If it is overcharged, it will reduce the life and possible be damaged. And damaged in a way that is dangerous.

Assuming the device is properly designed, there is no real problem with leaving them plugged in.

[burnafterreading]

Originally Posted by davidfor

No, you have it wrong. All devices with rechargeable Li-Ion batteries will not use the battery at all when they are plugged in. They will be running off the power while charging the battery. Once the battery is fully charged, the charging circuit will be turned off and the battery will sit idle until you unplug the device. This is done to prevent damage to the battery. If it is overcharged, it will reduce the life and possible be damaged. And damaged in a way that is dangerous.

Assuming the device is properly designed, there is no real problem with leaving them plugged in.

incorrect as far as your claim that ALL devices not using a battery when plugged in.

my Galaxy Nexus has a removable battery (a Li-ion), and when plugged in with a microUSB cord, it'll charge the battery. while running, removing the battery causes the phone to completely shut off, and the power flowing from the USB charging port will not keep it turned on. and this is just a smartphone, not a power-hungry tablet. this is dead-easy to actually check on a case-by-case basis on any device in which you can remove the battery while using the device.

there's (at least) 2 ways of designing a device to run on AC-plus-DC

1 - AC charges battery only. battery feeds power to device. separate circuits.
2 - AC feeds power to device and charging circuit. when AC is gone, internal circuit switches to draw power from battery.

#1 is how most portable devices behave. there's NO interruption of power as long as the battery is connected (and in many cases, the battery is not easily replaceable anyways, so it's a safe bet)

#2 is how most affordable UPS / power backup systems work. the connected devices (pc, tv, etc) are usually able to handle a short blip in power (like one missing cycle from the 60Hz line frequency)