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Thread: GMB-486UN - question about the external battery

  1. #1

    Default GMB-486UN - question about the external battery

    Hello,

    I'd like to add an external battery on my old 486 computer. The mainboard itself is a GMB-486UN, which had a barrel battery. Due to the battery leaking, I want to add an external battery. I now have problems identifying what I exactly need.

    The conector JP1 has the following PINs:
    -Pin1: VDD (6V)
    -Pin2: Unused
    -Pin3: Ground
    -Pin4: Ground

    As I already read in multiple sources, there are 4,5V and 6V possibilities for Pin1. According to my manual of that board I have the 6V.

    And I also read different solutions for adding an external battery. Since I'd like to add a rechargeable battery (there are many 3,6V rechargeable batteries on the market) I don't think that I need a diode between the + of the battery and the +6V-PIN.

    All I want to know is, is it really that simple connecting a new 3,6V rechargeable battery to the board (+ on the +6V-PIN and - to ground) or do I need to add any other components? I already tried to search for suitable batteries and found the Varta 3/CP300H which I would choose. The only thing which confuses me is that the connector has 6V, but the battery only 3,6V.

    Or may I just use 3x 1,2V AA rechargeable batteries with a diode? Can anyone recommend me something?

  2. #2
    Join Date
    May 2006
    Location
    Melbourne, Australia
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    Default

    Quote Originally Posted by Ghirahim View Post
    Hello,
    Welcome to these forums.

    Quote Originally Posted by Ghirahim View Post
    ... Due to the battery leaking, I want to add an external battery ...
    ... The conector JP1 has the following PINs: ...
    Yes, the user's guide for the GMB-486UN indicates that JP1 is for an 'external' battery.

    Quote Originally Posted by Ghirahim View Post
    All I want to know is, is it really that simple connecting a new 3,6V rechargeable battery to the board (+ on the +6V-PIN and - to ground) or do I need to add any other components? I already tried to search for suitable batteries and found the Varta 3/CP300H which I would choose. The only thing which confuses me is that the connector has 6V, but the battery only 3,6V.
    Or may I just use 3x 1,2V AA rechargeable batteries with a diode?
    Read the information at [here].

    From that, the 'external battery' connector is designed for a non-rechargeable battery (no battery charging circuitry for the 'external battery' connector).

    Also, there is a possibility that 3.6V is not enough voltage for the 'external battery' connector of the GMB-486UN. The user's guide for the GMB-486UN simply indicates "6V". How much lower than 6V that you can go depends on the design of the GMB-486UN

    Quote Originally Posted by Ghirahim View Post
    Can anyone recommend me something?
    Some possible options are shown at [here].

  3. #3
    Join Date
    May 2006
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    Quote Originally Posted by Ghirahim View Post
    All I want to know is, is it really that simple connecting a new 3,6V rechargeable battery to the board (+ on the +6V-PIN and - to ground) or do I need to add any other components?
    No other components are required if you want to go down the (unusual) route of connecting a rechargeable battery to a connector that will not charge the battery.

    As I stated before, there is possibility that 3.6V may be inadequate for your motherboard.

    Also, if the battery has been 'sitting on the shelf' for a long time, the 3.6V battery may have self-discharged to a voltage significantly lower; the seller expecting that a rechargeable battery is going to be connected to circuitry that occasionally charges the battery.

  4. #4

    Default

    All you really need is a battery holder with three or four AA batteries. Either will work. They're easy to find and cheap on eBay.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  5. #5
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    Pacific Northwest, USA
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    I must be getting old--I'm pretty sure that this question has been asked and answered at least a dozen times over the years.

  6. #6

    Default

    Right on both counts...
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

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