Results 1 to 5 of 5

Thread: 12 volt to mobo

  1. #1
    Join Date
    Jul 2012

    12 volt to mobo

    Can I do away with the AC inverter and just plug into 12v from the car or do i need to worry about the starter cranking? do i need to but a capacitor inline in protect the mobo when the starter cranks?

    City Net ITP15080B Pico Power Supply 150W Power Kit Pico PSU

    Audison Bit one
    Arc Audio
    Focal KRX3
    JL 13tw5

  2. #2
    Neither darque nor pervert DarquePervert's Avatar
    Join Date
    Apr 2004
    You need to worry about the unregulated 12v from your car's electrical system.
    Have you looked in the FAQ yet?
    How about the Wiki?

    Under normal circumstances, a signature would go here.

  3. #3
    MySQL Error soundman98's Avatar
    Join Date
    Jan 2008
    on the border of northern IL/IN
    Quote Originally Posted by DarquePervert View Post
    You need to worry about the unregulated 12v from your car's electrical system.
    ...because while a cars electrical system is stated as being 12v, at various points, the voltage can be as low as 5v to as high as 20v or more. you need buck/boost regulation to account for that.

  4. #4
    Raw Wave
    Join Date
    Nov 2009
    A good "automotive" ATX supply might or should ride through cranking dips. A good battery should not dip below 9V else 8V and some 12V (auto) supplies work down to 8V & 6V.
    Otherwise you need a 2nd battery to hold up the mobo.

    A 2nd battery is popular anyhow as a means of separating PC power from the vehicle power for cranking dips etc as well as not flattening the main/cranking battery in case the PC is left on. It can also provide cleaner power for the PC (or audio) etc. (A battery is essentially like a BIG cap - only cheaper, and with far greater reserve time.)
    AGM batteries are used (ie, sealed; hence legal for "internal" use) with 12V 7AH being a popular size unless larger is required.

    An (automatic) battery isolator is essential so that the batteries are isolated when NOT being charged (ie, the engine not running hence alternator not charging).
    But that can be as simple as a relay triggered by the alternator's charge-lamp circuit - search for "UIBI" & oldspark for some examples...
    And don't forget protection for the battery interlink at EACH battery end. Protection means fuses, though I suggest self-resetting circuit breakers which are cheap (~$8) for circuits up to 50A. [You must dimension the relay and cable for the PC/mobo current PLUS battery recharge current. The latter is difficult to predict and IMO there isn't much worse than a blown fuse that you don't know about, hence the self-resetting circuit breakers in case a very flat battery causes a huge initial charge current thereby blowing the interlink fuse(s) and eventually losing the PC or fridge etc and killing their battery.]

    A capacitor is not an efficient method of providing "gap" power. Batteries are cheaper, and they hold up for minutes or hours unlike the seconds for cas.

    The PICO supplies I have seen are for "12V" meaning non-battery systems.
    Automotive 12V (battery) systems are typically up to ~14.5V when charging; ~12.5V - 11.5V when not charging; and lower with heavier loads & cranking. But 16V is a typical "minimum" upper design voltage and IMO 8V is a reasonable "lower" design limit (ie, loads should handle 8-16V). But they also need transient/spike protection for higher voltages (eg, spikes of 100V-200V etc).

  5. #5
    MySQL Error soundman98's Avatar
    Join Date
    Jan 2008
    on the border of northern IL/IN
    so you need to look at power supplies like the m3 instead of the picopsu to deal with the cars voltages..

Similar Threads

  1. Regulated 12 volt to 5 volt conversion - Howto?
    By psyclobe in forum Power Supplies
    Replies: 7
    Last Post: 04-21-2010, 06:24 PM
  2. Replies: 5
    Last Post: 04-09-2010, 12:57 PM
  3. Replies: 9
    Last Post: 05-27-2008, 02:11 AM
  4. Power supply dillema -DC/DC 12 volt to 18 Volt
    By sniper222002 in forum Power Supplies
    Replies: 3
    Last Post: 04-08-2007, 01:00 PM
  5. 3 volt AC from dc?????
    By saletel in forum Power Supplies
    Replies: 6
    Last Post: 07-30-2002, 05:42 PM


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts