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Thread: Problem with battery drain

  1. #1
    Variable Bitrate Splash-X's Avatar
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    Problem with battery drain

    This is a tricky question for me since I don't know what area it should go in.

    I'm having battery drain overnight from the computer. More comments below my diagrams. I have a M2-ATX PSU.



    Diagram 1 shows how I supplied power to both the PC and AMP. I'm using a lilliput in-dash screen so the power for that comes from the radio harness

    http://www.911pcrepairs.com/images/car_in.jpg




    Diagram 2 shows how I power the rest of the devices in the car

    http://www.911pcrepairs.com/images/car_out.jpg




    Computer turns on fine after cranking. Amp works , screen works. PC Boots, hubs are active, everything works. If turn off the car the PC shuts down and the amp goes off. The USB hubs remain powered and you can push the button to open/close the USB-CDROM and it opens/closes. That tells me that there is still power coming from the PSU. One HUB has a blue LED that glows so I know it is active.

    The setup does the SAME thing if you use the Shutdown in windows to power off the PC.


    Whats going on? The power only stops if you unplug the red wire to the PSU and then plug it back in. What gives? If I dont do that unplug and plug in step the computer drains my battery overnight and the next morning its a dead batter (thank god for a battery jumper).

  2. #2
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    I had the same problem when using the onboard supplied usb ports. Although my battery didn't drain, but it was very annoying because my usb hub has a light and u can see it at night from outside the car. To fix it I used the USB ports that are supplied by the computer's case (the ones that connect to the motherboard). Or maybe if you buy a pci usb card, that might work.

  3. #3
    Variable Bitrate Splash-X's Avatar
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    The Hubs arn't getting their power from the USB cable, they are powered by the power jack. This tells me it is something to do with the PSU because my CD-Rom HAS to be plugged in to work. The amount of power supplied by a single USB port isn't enough to power my device.

    That said, it is either something wrong with my wiring, a faulty PSU, or I simply don't know what.

  4. #4
    Variable Bitrate billmee's Avatar
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    Quote Originally Posted by Splash-X View Post
    The Hubs arn't getting their power from the USB cable, they are powered by the power jack. .
    Did you modify your USB cable or HUB to eliminate the connection to +5V supplied by the mobo?

    If not the hub is drawing power from your psu standby circuit.

    Quick check- pull the USB cable from the pc for an overnight.

  5. #5
    Variable Bitrate Splash-X's Avatar
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    No modifications were made to the hubs so I'm assuming that I will need to do that.

    A side question, would a better idea be to some how place a switch on the power cable running to the computer? That would also allow me to turn on/off the PC if needed without shutting the car on/off.

  6. #6
    Variable Bitrate billmee's Avatar
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    Quote Originally Posted by Splash-X View Post
    No modifications were made to the hubs so I'm assuming that I will need to do that.

    A side question, would a better idea be to some how place a switch on the power cable running to the computer? That would also allow me to turn on/off the PC if needed without shutting the car on/off.
    The mod to the USB cable is pretty quick / painless. You just have to figure out which of the 4 wires is the 5 volts and cut.

    I use a switch on the dash to control a relay that makes or breaks the 12volt connection to my psu. My car had a cd changer option in the truck so an unsued cable that runs from the dash to the trunk carries the relay signal, as well as power for my LCD and USB hub.

  7. #7
    Newbie Timecloud's Avatar
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    I would say that putting the switch on the power lead to the PSU would be your best/easiest solution. It would also let you turn it on/off at leisure.
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    Variable Bitrate Splash-X's Avatar
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    It has been a long time since I've done switches for things in the car. I've installed many fog lights in the past and neons but we're talking 7 years and I was a novice.

    A switch would be the equilivent of running the red power to the switch, ground the switch, and then run the power out to the computer. Is that right?

  9. #9
    FLAC Jahntassa's Avatar
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    Quote Originally Posted by Splash-X View Post
    A switch would be the equilivent of running the red power to the switch, ground the switch, and then run the power out to the computer. Is that right?
    If the switch has a light in it, yes. Otherwise it's just going to have two prongs, just an in and an out. So one prong would go to the battery, the other to the PC

  10. #10
    Variable Bitrate billmee's Avatar
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    If you are doing a switch you need to know how much current you are drawing. The greater the load the larger the switch. If the switch becomes too large for your planned location ( dash etc ) you will probable want to use a relay.

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