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Thread: DC Voltage Brown Outs ? ? Need Help...

  1. #1
    Newbie
    Join Date
    Feb 2003
    Location
    SE Ohio
    Posts
    54

    DC Voltage Brown Outs ? ? Need Help...

    Currently I'm having some finnicky problems with the power supply system. The power transfer goes like this.

    12vdc from Alternator/Battery -> 330W(rms) Inverter (which outputs) -> 120vac -> 320W PSU -> Computer.

    This method though it sucks, is the cheapest way to go, and also lets me re-use any one of the power supply components if I were to un-install the carPC. DC->DC power supplies are available, but are extremely expensive ($160+). Therefore I chose to go the easy way (or so it seemed @ the time)

    I DO have an 450W / 700VA APC UPS (SU700-NET) that has a pure sine-wave output & under/over-voltage correction. Problem is even with it fully charged up, it will NOT turn on when plugged into the inverter, even though the computer pulls less Wattage than what would be the max RMS power rating for the inverter. I do know that the model I have does have a "Site Wiring Fault" inidicator, and that might be stopping the UPS from powering up but I'm not sure. I need to look into this. If anyone has had similar problems please get ahold of me. However running the carPC w/o the UPS to filter the AC electricity doesn't seem to have any adverse effects on the computer.

    I think it has something to do with the "Site Wiring Fault" protection that it has built into it. The "Site Wiring Fault" light comes on, so I think I need to make sure that:
    • All Cases Commonly Grounded (DC->AC Inverter), UPS, & carPC
    • Negative Prong on 120vac is Connected to Common Ground (Car Frame)


    My problem, I believe, is low voltage. Upon backing out of a parking spot, stopping @ night, or in slow traffic when the engine RPM's are low (less than 900) the low voltage alarm on the Inverter sounds and sometimes the inverter will turn off, thus in effect Hard-Turn-Off of the computer every hour or so. It's worse @ night when the running & headlights are on.
    (mind you all that extra stuff in my sig, (the CB, 2-Way Radio Radios, Stereo, etc) are all OFF only thing running is the Car, & the carPC.)

    I'm *NOT* having a problem with the car not starting after a long day of war-driving. My problem is the power shutdowns. It's probably going to kill my hardware. I believe I need a large Capacitor. Possibly 1/2 farad or 1 farad similar to the types used in the hard-core car-stereo competitions.

    I do have a 63Amp alternator that's not yet been installed. This was intended to power the computer system while the car was running, and the UPS was intended to allow me to run the computer for short periods of time. (basically shutdown after Ignition key in Off position, Power Chute system).

    Any thought or input would be greatly appreciated.

    Later for now. I'll keep you guys updated.
    If you're not paranoid, then you're not paying enough attention. -kmfdmk.com
    http://www.mymp3car.com/MP3Car/PSUpower.asp

    1985 Supra 7M-GTE
    10.4" Planar LCD
    ECS GOAL3+ mobo w/ 512mb + 8GB sdhc
    Edimax EW7318USG Wifi w/ 7 db Ant.
    USB GPS

  2. #2
    Newbie
    Join Date
    Feb 2003
    Location
    SE Ohio
    Posts
    54
    *bump*
    If you're not paranoid, then you're not paying enough attention. -kmfdmk.com
    http://www.mymp3car.com/MP3Car/PSUpower.asp

    1985 Supra 7M-GTE
    10.4" Planar LCD
    ECS GOAL3+ mobo w/ 512mb + 8GB sdhc
    Edimax EW7318USG Wifi w/ 7 db Ant.
    USB GPS

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