iPhone 9V Emergency Charger

seanwes

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Feb 13, 2008
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#1
Has anyone tried the iPhone emergency charger at Handheld Items? I'm wondering how much of a charge you can get from 9V.
 
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dturner

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Dec 15, 2007
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#2
I'm sure it is good for what it states and that is for emergencies. Wouldn't want to depend on it as a full fledged charger.
 

seanwes

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#3
I'm sure it is good for what it states and that is for emergencies. Wouldn't want to depend on it as a full fledged charger.
Yeah, i wouldn't either. I was hoping someone had tried it, as i wanted to know how much of a charge you could get from it.
 

dturner

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#4
I was hoping someone had tried it, as i wanted to know how much of a charge you could get from it.
:laugh2: I just went to the link you posted and IMO the answer is there. Went from $19.99 to $4.99. Sends a red flag to me.:laugh2:
 

JoeT

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Dec 18, 2007
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#5
Well, check the mAh rating on the battery, and figure probably 10-15% loss due to inefficiency and the voltage conversion.

A quick check of an Energizer alkaline 9v battery reveals a capacity of 625mAh - or a little less than half of the 1450mAh 2G iPhone's battery, so at BEST, you could only charge it to roughly 40-45% charge factoring in losses. (Note: I haven't yet seen official specs from Apple on the capacity of the 3G's battery)


Energizer AA batteries have a capacity of 2850mAh - or about double the 2G iPhone's battery. HOWEVER, each cell is 1.5 volts, so for this to be valid, we have to have a higher voltage than the 5.5 volts that the iPhone charges at. So if you connect 4 AAs in series, that would give you a 6.0v battery pack, which could charge the iPhone. However, many popular AA chargers have only TWO AA batteries, so the 3v must be transformed to 6v at a loss. Further, your 3v, 2850mAh battery pack is effectively a 6v, 1425mAh pack - so when you factor in losses, it still will not quite fully charge a 1450mAh battery.

So while the 9v holder could make a decent "holy crap, my battery is DEAD and I need to make a call NOW" type charger, don't expect much from it.
 
Jul 23, 2008
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#6
Well, check the mAh rating on the battery, and figure probably 10-15% loss due to inefficiency and the voltage conversion.

A quick check of an Energizer alkaline 9v battery reveals a capacity of 625mAh - or a little less than half of the 1450mAh 2G iPhone's battery, so at BEST, you could only charge it to roughly 40-45% charge factoring in losses. (Note: I haven't yet seen official specs from Apple on the capacity of the 3G's battery)


Energizer AA batteries have a capacity of 2850mAh - or about double the 2G iPhone's battery. HOWEVER, each cell is 1.5 volts, so for this to be valid, we have to have a higher voltage than the 5.5 volts that the iPhone charges at. So if you connect 4 AAs in series, that would give you a 6.0v battery pack, which could charge the iPhone. However, many popular AA chargers have only TWO AA batteries, so the 3v must be transformed to 6v at a loss. Further, your 3v, 2850mAh battery pack is effectively a 6v, 1425mAh pack - so when you factor in losses, it still will not quite fully charge a 1450mAh battery.

So while the 9v holder could make a decent "holy crap, my battery is DEAD and I need to make a call NOW" type charger, don't expect much from it.
"Wow"! You just made my head spin but that's one of the most thorough answers I've ever seen! "Thanks"! Even though I didn't ask the question. :)
 

JoeT

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Dec 18, 2007
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#7
LOL! No problem. I've posted on the subject before, but there's so many charging solutions out there that I wind up reposting periodically. Try searching, I posted a more easily understood version some time back.