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Old 11-30-2012, 08:25 PM   #1
monkey333
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Default Power requirements

I posted this in mobile devices forum, but got no answer.
Got a tablet that has a 2.5 amp charger. I also but a speaker dock, which is supposed to charge certain devices, but only outputs 1 amp for charging. Will I run into any issues "under powering" the tablet? Will it burn out the speaker dock?

Thx.
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Old 12-01-2012, 03:28 AM   #2
esun
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You'll probably notice that your tablet charges very slowly (or maybe not at all under heavy use). That's the only issue you'll see.
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Old 12-01-2012, 07:21 AM   #3
monkey333
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Quote:
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You'll probably notice that your tablet charges very slowly (or maybe not at all under heavy use). That's the only issue you'll see.

I don't see that as a huge issue as there will be plenty of idle time, so I would imagine then it would charge?
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Old 12-01-2012, 10:57 AM   #4
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No, overloading a power supply is not free from risks.
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Old 12-03-2012, 11:36 AM   #5
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It really depends on the tablet, somehow it should sense it's own charger and try to draw the 2.5 amps. If you connect it to something else and it uses a standard usb connector, it should either only attempt to draw the usb standard 500mA or somehow it will also sense the 1A capacity of the speaker dock and draw that. If the tablet is poorly designed, it will just try to draw 2.5A all the time, at which point you'll run into problems. The tablet should come with a warning not to use other chargers in that case. Also, it could give a warning of unauthorized charger from the device.

If the speaker dock isn't designed to protect itself from overload, it will quickly overheat and fry from the extra draw. Hopefully it would have some sort of over current protection(OCP).
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Old 12-04-2012, 04:49 PM   #6
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The tablet may not charge at all. Some tablets will detect if there is insufficient power available to charge and so to avoid any damage will refuse to charge.
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Old 12-05-2012, 12:10 PM   #7
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Quote:
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The tablet may not charge at all. Some tablets will detect if there is insufficient power available to charge and so to avoid any damage will refuse to charge.
This. There is probably no danger to the power supply because a simple current limiting resistor is usually in line to prevent dead shorts or other overloads. In other words, if the output is stated as 1 amp @ whatever voltage, it probably CAN'T put out more than that.
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Old 12-05-2012, 10:55 PM   #8
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Is this a smart power supply?
Many devices use the additional pins on micro and mini USB connectors to tell the power supply capability so the device can act accordingly.

For example, Garmin GPSs open/close or add some resistive value on the 5th pin on its Mini USB port to tell if its a Garmin's 1A power cord or 500mA USB source.

if you plug in a connector that tells the device its hooked up to a 2.5A supply, it will overload the PSU which will result in overheat (2.5A is a mild over load, compared to a short) or it will go into an endless power cycling.
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