Newbe question dc/dc converter

Discussion in 'The Projects Forum' started by Mike Axe, Dec 31, 2014.

  1. Mike Axe

    Thread Starter New Member

    Dec 31, 2014
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    Hello everyone,
    I would expect this to be easy for most of you but I enjoy making a fool out of myself so much. First of all, allow me to say hello and thank you in advance for your help. My name is Mike and I want to take a forklift battery (80vdc) and make a simple inverter to produce 12vdc output for lights, horn, back-up alarm and other driver interface systems. I am new to this and a simple regulated converter design would be of great help. I can build it from there.
    Thank you in advance of any help you can give me.
    Mike
     
  2. wayneh

    Expert

    Sep 9, 2010
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    Are you certain that the battery itself cannot be configured to provide 12V?

    Do you know how much current at 12V you will want? This will define what specs you need to aim for. You MIGHT be able to find a suitable DC-DC converter on e-bay very cheaply. 80V is higher than most you'll see there but perhaps you'll get lucky.
     
  3. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    I don't know how many lights you have but since, I am guessing, they constitute most of the load you could consider using 3x 24V lamps in series to run directly from 80V. This could considerably reduce the size and cost of the DC-DC converter.
     
  4. Mike Axe

    Thread Starter New Member

    Dec 31, 2014
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    The maximum amperage will be 15 amps fully loaded. I can tap off of enough cells on the battery but that will eventually ruin the cells, I know this from experience. I cant believe this would be very expensive using a LM5008 Step-down chip.
     
  5. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    I wasn't aware that the LM5008 can deliver 15A.
     
  6. ronv

    AAC Fanatic!

    Nov 12, 2008
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    You could probably build a real simple one since it is just for light etc. The problem is the price of the inductor. Think $50.00 for a 20 amp one.
     
  7. Mike Axe

    Thread Starter New Member

    Dec 31, 2014
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    I want to build one but I need the expertise of this group to show me how to do it. I don't mind spending the money if it works. Can someone provide me some instructions? Thank you
     
  8. tcmtech

    Well-Known Member

    Nov 4, 2013
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    Off the shelf DC- DC buck converters can be found on eBay for around $40 - $50 that will work with that input voltage and output power levels.

    Unless you have a lot of higher powered scrap electronics to rob parts like power transistors and large inductors from you will likely never build your own for anywhere near what you can buy a unit for.

    That said if you are really wanting to spend the money and time I think we can help you out! :cool:
     
  9. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    Can you provide a breakdown of exactly what 12V devices are to be powered and what their current requirements are?
     
  10. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Bypassing the rectifier part of a standard 120Vac-input SMPS 12Vdc power supply, and feeding the 80Vdc from the battery right to the input filter capacitor might work. The switcher part, transformer, isolation, output regulation should all work to produce the 12Vdc output.
     
  11. Mike Axe

    Thread Starter New Member

    Dec 31, 2014
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    Power requirements are similar to a car, lights, horn, alarm, turn signals, etc. Current requirements should not exceed 15 amps at any given time.
     
  12. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    These items have a large peak to average duty cycle. I believe you would do better to use a SMPS converter/battery charger (rated at ~5A), and then use a small SLA 12V battery to run the loads. That way, the peak current can come from the battery, while the converter only has to supply the average current plus a little to recharge the battery.
     
  13. ronv

    AAC Fanatic!

    Nov 12, 2008
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