AA Battery Booster

Discussion in 'Android Accessories' started by Silverwing, Dec 15, 2009.

  1. Silverwing

    Silverwing Member

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  2. raven1911

    raven1911 Member

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    Wondering if you have to use alkaline batteries with this as well? Would it be possible to use rechargeable batteries with this device??
     
  3. kilo

    kilo New Member

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    cool beans
     
  4. ldimick

    ldimick Member

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    Guys. Do the math. AA batteries have what, 1800 or 1900 mAh? Our Droid holds 1300 or 1400? There is no way that you can get 2.5 charges out of that thing. You can get 1.3 charges or so. But it is certainly a good option. Or you can wait for the Zagg device to come back on sale. 6000 mAh for $49 yesterday. And it is completely rechargeable. and can be used on any device that has a USB charger.
     
  5. ldimick

    ldimick Member

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    Yes you can use rechargeable batteries. However, they typically have a lower mAh capacity and would not be as effective.
     
  6. Silverwing

    Silverwing Member

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    How can 4 AA batteries not charge a device 2.5 times. I do not understand your math, at all.

    Using Sanyo Eneloop:

    http://www.amazon.com/SANYO-eneloop...2?ie=UTF8&s=electronics&qid=1260952499&sr=8-2

    That is 8,000 mAh, at almost 5 volts. charging the droid's 1,400 mAh, which is 3.7 volts. So I am really confused by your math.

    Anyway, with all that said, is that merchant reliable and is this device safe? Has anybody used it, read reviews or know anybody who has used it?

    Are the batteries even replaceable in this device?
     
    Last edited: Dec 16, 2009
  7. TheOldFart

    TheOldFart Active Member

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    That is not 8000 mAh at 5 volts. It is 8000 mAh at 1.3 volts if the batteries are in parallel.. If the batteries are in series then it is only 2000 mAh at 4 x 1.3 = 5.2 volts. You can't multiple BOTH the charge level and the voltage by the number of batteries.
     
  8. Silverwing

    Silverwing Member

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    Can you multiply both by two then, so two in series, two in parallel: that is 2.6 volts and 4000 mAh?
     
  9. TheOldFart

    TheOldFart Active Member

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    Yes, that is correct.
     
  10. TheOldFart

    TheOldFart Active Member

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    The charger that comes with the Droid is a 5.1 volt charger. The nominal voltage of a NiMH battery is 1.2 volts and is pretty constant throughout the discharge cycle. That would make 4 in series 4.8 volts. They are available in capacities up to about 2900 mAh. The Droid battery voltage is 3.7 volts. This would indicate to me that its 1400 mAh battery could be recharged twice from completely dead by 2900 mAh batteries. Even though there is more energy in the 4 NiMH batteries because of the higher voltage, there are losses in the charging circuit. I have no idea how much though. Since it is not a good idea to allow the Driod's battery to run completely down, you could probably get nearly 3 recharges if you recharge at say 25%. That would be 2900 / (0.75 x 1400) = 2.76 recharges. I would imagine it would be somewhat less than this though.
     
  11. Silverwing

    Silverwing Member

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    So, the only question that remains is.....is this device safe and reliable? I don't want to melt my Droid =)
     
  12. TheOldFart

    TheOldFart Active Member

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    I'm not qualified to give an absolute answer, but here are my thoughts. If you use NiMH batteries then the voltage would be 4.8 volts. I don't think this would cause any problem. However, if you were to use alkaline batteries, the initial voltage could be 6.0 volts. I would be concerned about this higher voltage, but I honestly don't know if it could damage the Droid.

    I would also like to hear other people's thoughts or experiences on this.
     
  13. mbeatle

    mbeatle Member

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    OldFart has already explained things pretty well, but to directly compare the two batteries on equal terms, convert each to watt-hours

    Droid:
    1500mah x 3.7v = 5.55 watt-hours

    Eneloops:
    4 x 2000mah x 1.2v = 9.6 watt-hours

    I'd say you could likely get 2 full charges out of a set of Eneloops without an issue. I'm not sure at what voltage the Droid shuts off the device, but you may not fully empty the battery before it reaches the low-voltage threshold.

    I'll just wait for Seidio's extended battery. :)
     
  14. Silverwing

    Silverwing Member

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  15. TheOldFart

    TheOldFart Active Member

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    2 x 12 Ah x 1.2 v = 28.8 watt-hours, not 57.6. Besides, you would need 4 batteries to get enough voltage and then that would equal 57.6 watt-hours.
     
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