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Distinguished Correspondent
nlstein
Posts: 314
Registered: ‎12-23-2009
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Nook power supply (AC charger) question

I know that the nook's power supply (AC charger) provides up to .85A (850mA) @ 5VDC. I have my iPhone charger that can supply up to 1A (1000mA) also @ 5VDC. Does anyone know if I can use the iPhone charger without causing any damage? I emailed to B&N tech support several days ago but have received no reply. I know the special "charging circuitry" has to be in the nook itself since it charges from the AC adaptor and/or a USB port. The question is, does the nook have current limiting? I need this answer since I travel and would like to carry as little as possible. I could simply use the nook supply to charge my iPhone and the nook but that will take longer since the nook supply delivers slightly less current.

 

Anyone?

MacBoy
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GeoffreyF
Posts: 202
Registered: ‎12-15-2009
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Re: Nook power supply (AC charger) question

It doesn't matter how much current the charger provides.   In fact, a higher current charger is better.   The nook only takes what it needs.   Voltage needs to be the standard for USB which the apple charger and nook charger both are.   if current is BELOW 850 ma then the nook may not charge, especially if very low on battery.

 

You are right, the nook supply may take longer to charge the iPhone or perhaps not work.  However, you may have read the Input current (what the charger draws from the AC) and not the output current.  I actually think the iPhone is the same, 850ma.    Apple plays some funny games so people will buy their overpriced chargers.  For this reason, the iPhone may not work with the nook charger.

 

Pretty much any USB charger that delivers at least 850 ma and is (lets be safe) a name brand, is safe for the nook.

Inspired Wordsmith
icebike
Posts: 4,434
Registered: ‎11-30-2009
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Re: Nook power supply (AC charger) question

> if current is BELOW 850 ma then the nook may not charge, especially if very low on battery.

 

No, it will charge just fine on less than 850ma, only slightly slower.

 

After all, you can charge from your computer which only puts out .5 amps. 

The iphone too charges from a pc or a car charger, which are usually .5 amps.

 

 

Distinguished Correspondent
nlstein
Posts: 314
Registered: ‎12-23-2009
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Re: Nook power supply (AC charger) question

[ Edited ]

Unless I've miss-read it, the small iPhone charger (little cube) shows 1A as the output.

MacBoy
Inspired Contributor
GeoffreyF
Posts: 202
Registered: ‎12-15-2009
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Re: Nook power supply (AC charger) question

The amount of current that any device requires varies.

 

I haven't had the nook long enough to know but .5 amperes might not charge it in all cases.   Best to be safe than sorry.  That was my only point.   Yes, it will charge with .5 amperes but ... I'm not sure that either of us know if that will work in all possible discharged conditions.

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icebike
Posts: 4,434
Registered: ‎11-30-2009
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Re: Nook power supply (AC charger) question

 


GeoffreyF wrote:

The amount of current that any device requires varies.

 

I haven't had the nook long enough to know but .5 amperes might not charge it in all cases.   Best to be safe than sorry.  That was my only point.   Yes, it will charge with .5 amperes but ... I'm not sure that either of us know if that will work in all possible discharged conditions.


 

 

It doesn't have to charge it in all cases, it just has to charge it when its sleeping. 

Who charges while reading?

 

Even if it didn't charge with all radio's on it wouldn't matter because the duty cycle on the

radios is so short.

 

While reading, the nook is hardly using any power at all, the processor is idleing,

just watching the touch screen for a swipe.

 

B&N specifically states it will charge from a PC USB port, which are .5 amps, but I have watched it charge by viewing the settings display on 400 ma using my Minty Boost. 
http://bookclubs.barnesandnoble.com/t5/eBooks-Help-Board/To-charge-your-nook-w-o-a-c/m-p/457647#M289...

 

 

Distinguished Correspondent
nlstein
Posts: 314
Registered: ‎12-23-2009
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Re: Nook power supply (AC charger) question

Okay, a little electronics 101.

 

1. The "special" charging circuitry for the nook battery is in the nook itself - not the AC charger. This is obvious since the nook charges from the adaptor AND a standard USB port. So, no worry about charging it from things other than the AC adaptor that comes with it.

 

2. The standard USB port spec (as defined by the USB police) is 5VDC @ .5A. Most newer computers provide this at any/all of its USB ports. This means that the nook should charge (all be it slower than from a higher current AC adaptor) from any USB port in a modern computer. You can't hurt it if your port puts out a little less current - it'll just charge slower.

 

3. Properly designed electronics only draw the amount of current they need. This means (for instance) that if an item needs .85A but the AC adaptor can deliver 1A you can't hurt the nook since it will only draw .85A from the charger.

 

4. All of this means that the nook should charge fine from any adaptor that is designed to charge an item that can charge from a standard USB port. This would include the AC adaptor for the iPhone (the little cube is rated at 5VDC@1A output) and any USB external battery (there are any number of these out there-they are simply rechargeable batteries that can be charged and then used to charge something else like the nook or a cell phone). If properly designed (and this is electronics 102 that any EE should have passed) the nook charging circuit has a current limiter that only allows it to draw what the battery needs to charge properly.

 

There is no voodoo to this - it's simple electronics. The nook should charge fine with airplane mode on or off, awake or asleep. The battery needs a few charge/discharge/charge cycles to get the percentage display to accurately display the state of charge.

 

This is not my opinion, it is physics.

 

If admin (or anyone with an EE degree) disagrees let's hear about it now. Otherwise I think this discussion (which I started) is over.

MacBoy