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[Q] Car Charger current limited by Nook?

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By nerdful1, Junior Member on 20th May 2011, 07:08 PM
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Does the nook on-board regulator have current limiting? Or are the wall warts and car power adapters limiting the maximum current.

I know the standard usb ports limit to 500ma in most cases, but with the appropriate cable and connections, the nook will request the higher USB ratings, 1.9 amps on my stock wall wart and stock power cord.

Are car chargers built with usb sockets limited to some usb spec of 2 amps or so?

A simple 5 volt regulator in a car socket could theoretically supply 10-30 amps depending on its fusing.


What I am wondering is say, a gell cell or NiCd pack with high current ability could be connected to the nook, using the high power usb pins enabled to on would be safe, or would the Nook be expecting a limited power source.

I'm afraid if i connect a 5v 10A plus source like above, and there is no self current limiting, I might blow an internal fuse or input resistor.


I want to take the thing on a trip, and was hoping a battery pack in my bag with a female USB jack (the center two pins shorted, and the stock cable) would be able to charge the unit when away from both the AC and car power.

Thanks.


P.S. On a related note, do airlines now have 120 volt outlets at all seats so I could use my nook charger?
 
 
25th May 2011, 07:49 AM |#2  
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Quote:
Originally Posted by nerdful1

Does the nook on-board regulator have current limiting? Or are the wall warts and car power adapters limiting the maximum current.

I know the standard usb ports limit to 500ma in most cases, but with the appropriate cable and connections, the nook will request the higher USB ratings, 1.9 amps on my stock wall wart and stock power cord.

Are car chargers built with usb sockets limited to some usb spec of 2 amps or so?

A simple 5 volt regulator in a car socket could theoretically supply 10-30 amps depending on its fusing.


What I am wondering is say, a gell cell or NiCd pack with high current ability could be connected to the nook, using the high power usb pins enabled to on would be safe, or would the Nook be expecting a limited power source.

I'm afraid if i connect a 5v 10A plus source like above, and there is no self current limiting, I might blow an internal fuse or input resistor.


I want to take the thing on a trip, and was hoping a battery pack in my bag with a female USB jack (the center two pins shorted, and the stock cable) would be able to charge the unit when away from both the AC and car power.

Thanks.


P.S. On a related note, do airlines now have 120 volt outlets at all seats so I could use my nook charger?

I'll answer the postscript first: Nope. It's a rare plane that has ANY 120 V outlets in coach. If you're willing to fork out the cash for first class it's probably a fifty-fifty chance.
25th May 2011, 08:01 AM |#3  
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Quote:
Originally Posted by nerdful1

Does the nook on-board regulator have current limiting? Or are the wall warts and car power adapters limiting the maximum current.

I know the standard usb ports limit to 500ma in most cases, but with the appropriate cable and connections, the nook will request the higher USB ratings, 1.9 amps on my stock wall wart and stock power cord.

Are car chargers built with usb sockets limited to some usb spec of 2 amps or so?

A simple 5 volt regulator in a car socket could theoretically supply 10-30 amps depending on its fusing.


What I am wondering is say, a gell cell or NiCd pack with high current ability could be connected to the nook, using the high power usb pins enabled to on would be safe, or would the Nook be expecting a limited power source.

I'm afraid if i connect a 5v 10A plus source like above, and there is no self current limiting, I might blow an internal fuse or input resistor.


I want to take the thing on a trip, and was hoping a battery pack in my bag with a female USB jack (the center two pins shorted, and the stock cable) would be able to charge the unit when away from both the AC and car power.

Thanks.


P.S. On a related note, do airlines now have 120 volt outlets at all seats so I could use my nook charger?

As to the current limiting, yes, most car chargers are pretty low power, usually rated to an amp or so. It's pretty hard to find one that will match the stock wall wart in amps.

I would be careful of a simple linear regulator in a car charger, as you'd be dumping a lot of power directly to heat. Each amp of current would put 5 watts out the usb port and burn 7 watts in the regulator. Won't take long to start a fire that way.

Now, lithium ion batteries normally have pretty sophisticated charge control circuitry, as too rapid of a charge could cause it to burst into flames. If you decide to test your idea make sure you have a good class C fire extinguisher handy!
25th September 2018, 12:40 PM |#4  
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To update my airplane power question of years ago: Since then, I've been traveling a lot and have found USA 120 volt outlets in all planes. Both in 1st and cramped class.
Also on Amtrak train and busses.
Going to poke around with my retired Nook Color for ham radio and bench schematics, etc.
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