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Thread: Difference chrging spec for 3G and 3GS

  1. #1
    Default Difference chrging spec for 3G and 3GS
    Hi I've just bought one of thease from ebay (Universal Portable Replacement BATTERY Pack For Mobile)Portable Replacement BATTERY Pack For Ipod Iphone on eBay (end time 16-Jun-10 00:06:51 BST)

    but can't get it ti work with my 3GS but it does work for my mates 3G.

    I've opened the connector and it has the pull up resistors on the datalines of the usb connector but it doesn't charge or indicate anything at all on my 3GS.
    Whats the difference between the charging requirements for the 3G and the 3GS. Do i need different value resistors.

  2. #2
    If it doesnt work in one it wont work in the other

  3. #3
    iPhone? More like MyPhone one_crazy_dude's Avatar
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    I belive they do have diffrent specs. When I bought the sync/charge cable for my car stereo there were 2. One for 3g @ 5volt and 3gs @ 12volts

  4. #4
    Quote Originally Posted by westerman View Post
    If it doesnt work in one it wont work in the other
    What do you mean. If it works with the 3g it wont work with the 3gs.

  5. #5

  6. #6
    The battery gives out 5.477 volts on the +v pin and then has a 4 resistor potential divider circuit to suplly two different voltages to the usb data lines. A 51k and 43k to provide 2.779 v to the D+ pin and then a 51k and a 75k to provide 2.045 to the D- line. I've tested the apple wall charger and it gives 5.16v on v+ 2.763 on D+ and 2.056v on D-. So i'm at a loss to see why its not charging. The battery is 4400 mAH so can supply the current needed. The iphone does not indicate anything is even plugged in. I've even tred using the data lines potential divider circuit out of my car charger and it still didn't work. Is the V+ from the battrey slightly to high.

  7. #7
    Some one told me to try adding a diode inline with the 5.5v line to drop it down to 5.0v which it did when the iphone was not connected. The iphone does detect it this time but says charging is not supported and will not charge. The voltage underload with iphone connected is now to low i think. 4.6v and the D+ and D- have dropped slightly as well. Dont know the rateing or type of the diode just unsoldered it from an old ethernet card. Will have to try a proper IN4001 when i can get one. I m thinking of getting a coupele of 100K preset pots so I can tweek the resistor circuit to finely tune the voltages for the D+ and D- lines but not sure how to get the 5.5v down to bang on 5v.

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