I need to build up DC/DC circuit

Discussion in 'The Projects Forum' started by odd boy, Jun 2, 2010.

  1. odd boy

    Thread Starter New Member

    Jun 2, 2010
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    Hi,

    I need to build up a circuit that has the following specs, or buy it if it is available:

    1. Output provides 15 VDC as out put
    2. Input power is 11 ~ 12 VDC
    3. Max Amp is 35 AMP

    Thanks,
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    What are you planning to use as an input power supply?

    35A @ 15V is a 525 Watt supply output. If the DC-DC converter is 90% efficient, you will need about 53A input at 11V.

    You will be hard-pressed to build something that efficient.
     
  3. odd boy

    Thread Starter New Member

    Jun 2, 2010
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    I will use it in car.... Car's battery can provide around 60 amp and 12 - 14 DCV in the presence of the alternator
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    You would be better off to add a 2nd alternator, and modify it's regulator to cause it to generate a 15v output. [eta] At a minimum, the 2nd alternator will need a large capacitor from its' output to ground, or the regulator will be destroyed immediately.


    If you don't go that route, you will need to upgrade your original alternator, and you will likely need to turn the supply off when your engine is running below about 1,200 RPM to keep from killing your battery.

    What's this 35A 15v supply supposed to power, anyway?
     
    Last edited: Jun 5, 2010
  5. John P

    AAC Fanatic!

    Oct 14, 2008
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    Yow. How about buying a portable generator?
     
  6. odd boy

    Thread Starter New Member

    Jun 2, 2010
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    Gents,

    Thanks for your reply, both options will not work with me because of the following:

    All of the car’s instruments need 12v – 13v, more than that it would do something beyond the need, like opining for longer time which might lead to extra example.

    I need to get 15 V in special cases not all the time and for one sensor only.

    If any is interested, I will explain the project thoroughly
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    One sensor that needs 15v @ 35A only upon occasion?

    What is this sensor?

    [eta]
    Don't use the custom fonts like you did in your last post. It makes your post much harder to read.
     
  8. odd boy

    Thread Starter New Member

    Jun 2, 2010
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    When you install turbo chargers on cars, you need to upgrade the fuel system by replacing the pump to a bigger (expensive one). We can resolve this issue by increasing the voltage of the original pump to 15V.
    Through a DC regulated power supply (bench style), we managed to provide constant 15V power to the pump and resolved the issue.
     
  9. Bychon

    Member

    Mar 12, 2010
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    That helps. A pump is not a sensor.
     
  10. odd boy

    Thread Starter New Member

    Jun 2, 2010
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    yeah, the pump it self. For simplicity I said sensor.
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    It'll probably cost about $400 to build a DC-DC converter supply, and it would overload the existing electrical system.

    Wouldn't it be easier to just buy the right fuel pump?
     
  12. odd boy

    Thread Starter New Member

    Jun 2, 2010
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    there is a similar system in the market with cost of 250$. I was thinking of making it myself....
     
  13. SgtWookie

    Expert

    Jul 17, 2007
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    If you can buy it for $250, why not just go that route?

    Do you really want to spend another $150 and have to build/debug it yourself?
     
  14. odd boy

    Thread Starter New Member

    Jun 2, 2010
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    no I'm looking for cheaper.
     
  15. SgtWookie

    Expert

    Jul 17, 2007
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    Then get an alternator for an imported car from the junkyard, modify the regulator to output 15v, and fashion a bracket to mount it to the engine.

    That will be a whole lot cheaper and much more simple than trying to build a 525 Watt DC-DC converter.
     
  16. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    How long is the turbo on, average, inporportion to total driving time? A little ancient history [1950-1963] : Instrument trucks used two battery systems, 12 & 14V, using 6V batteries with connecting straps cut on one to make 3- 2V cells. Charging via 12V & 14V alternators. I modified some by converting to straight 14V systems, one alternator, worked fine, nice bright driving lights & quick starting; all 7 then converted- but that was before every thing was electronic. If turbo time is relative short, a 2V battery , 50Ah, could be switched in via relay's and charged with buck converter from 12V system.
     
  17. SgtWookie

    Expert

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    Nice idea, Bernard. I like it. :)
     
  18. odd boy

    Thread Starter New Member

    Jun 2, 2010
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    In reality not more than 2 min, but for design will say Max time is 5 min
     
  19. Bernard

    AAC Fanatic!

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    For 5 min. expest a small 2V SLA battery should be OK.
     
  20. SgtWookie

    Expert

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    Ahhh, I think you might have problems if you tried to use a low-AH SLA.
     
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