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  1.    #1  
    So, I have this little guy:

    "iGo" powerXtender Charger at iGo, Inc.

    I have a variety of rechargeable AA batteries, among them the Duracell hybrid type-- essentially, so far as I can determine, a relabeled Sanyo Eneloop. These are rated as 2000 mAh at 1.2V. So, two of these in series would be about 2.4v, giving (2.4 * 2000) = 4.8 watt-hours. Considering the Pre battery similarly, its 1150 mAh battery at 3.2v should give about 3.7 watt-hours. So, in sum, since I'm confident that 4.8 > 3.7, these 2 AA rechargeables should be enough to fully charge the Pre battery.

    Obviously, though, that's not what's happening in reality or I wouldn't be posting. I charged from 5% to 58% with 2 freshly-charged batteries (analyzed and charged on a Maha MH-C9000) and could go no further. The iGo device simply shut off. I know that there are efficiency losses, but they shouldn't be nearly high enough to account for the difference. Does anyone have any ideas why this doesn't work?
  2. #2  
    i use this: Varta Backup Charger

    works well on the pre.
  3. #3  
    the sono solar charger is great,,very light,small,if it runs out of power all you need is sunlight to to charge with.i always leave house with it fully ready to charge my pre,even has a removible clip to attach it to something( belt,backpack).charges just as good as pluging into a wall.
  4.    #4  
    I appreciate the suggestions, and I'd like to get the Sono (saw one at the Sprint store, got fascinated...) but I'd also like to know what might be causing the AAs not to charge the Pre properly. There seems to be a huge disparity between the numbers and reality.
  5. #5  
    The Pre is expecting 5V to charge. I'm surprised you were able to get it to charge at all with only 2.4V. Put 4 together, you should be able to get to get about 9.6Ah out of it.
    Treo 300 > Hitachi G1000 > PPC-6700 > PPC-6800 (Mogul) > PPC-6850 (Touch Pro) > Palm Pre & HTC EVO Optimus V
  6. #6  
    Quote Originally Posted by froggersloth View Post
    I know that there are efficiency losses, but they shouldn't be nearly high enough to account for the difference. Does anyone have any ideas why this doesn't work?
    Chances are you were drawing current at higher voltage than the 1.2V where the batteries are rated.

    Maximum output for a AA battery is around 1.65V. Assuming with two batteries starting at ~3.3V together charging a 3.2V battery, that mAh rating is going to be significantly less than if you were draining at the 1.2V (2.4V combined) level.

    Plus, you have to consider that you can't suck every bit of juice from the charging batteries. There's going to be a threshold where the voltage drops too low to charge anymore. I'd say you got about the maximum performance from your setup.
  7.    #7  
    So, it sounds like my "analysis" was a little naive. On further research, I note that WebOS Internals suggests a 4-AA setup. I'll have to give that a try... shouldn't be too tough. Many thanks for the replies.

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