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  1. #1
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    Aug 2008
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    Default 24V to 12V wiring

    Recently purchased a second truck that I have derated to a car.

    Wanting to tow trailers (50mm ball towbar) but it is a 24V system. Would a few of those buck converters in a box work OK to convert the 24 to 12?

    I am sure someone makes such a device for a hefty sum of money but the buck converters can be had for a few dollars each.

    One for brake lights, one each for indicators and one for tail lights. Seems easy enough.
    Gold, the colour of choice for the discerning person.

  2. #2
    Join Date
    Sep 2012
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    York, North Yorkshire UK
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    Default

    Hi,

    I've done a similar thing, dropping a 12 volt vehicle supply down to 5 volts for USB power and led lighting. I take it that 24V bulbs are hard to come by ? The headlight bulbs, I would imagine are an issue with the high amount of power they require. Why not just tap off the batteries centre and get your 12 volts that way ?
    Best Regards:
    Baron J.

  3. #3
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    Baron it would convert the 24V to 12V at the trailer plug on the truck. So only the trailer gets 12V.
    Gold, the colour of choice for the discerning person.

  4. #4
    Join Date
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    NSW
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    I would change the trailer lights to LED lights . That would reduce the current draw quite a bit and then a cheap 24v to 12 volt converter could be installed .
    There is one on ebay that handles " allegedly " 30 amps so at 12 volt that's 360 watts of lights . So changing the lights may be unnecessary . The problem is wiring it in as each line is switched separately .
    I think several smaller ones on each line would be easier .
    The volume of a pizza of thickness 'a' and radius 'z' is given by pi z z a.

  5. #5
    Join Date
    Sep 2010
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    Lebrina
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    Default

    This is commonly done on trucks and Redarc among others sell converters specifically designed for converting trailer plugs from 24v to 12v.
    Simple, reliable and easy to fit.

  6. #6
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    Redarc make good stuff but most of their stuff is high priced and their support people a bit on the rude side . They do not warranty any product that is not fitted by an auto electrician . I don't bother with them .
    The volume of a pizza of thickness 'a' and radius 'z' is given by pi z z a.

  7. #7
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    Jun 2005
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    Helensburgh
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    LED lights usually have a voltage tolerance of 8V to 24V from memory so no reduction is required.
    CHRIS

  8. #8
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    near Warragul, Victoria
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    Quote Originally Posted by Retromilling View Post
    I would change the trailer lights to LED lights . That would reduce the current draw quite a bit .
    I agree , LEDS mean far less heat dissipation because of the much smaller currents involved. Maybe you could get away with simple resistors in series with the LEDS . The brake lights are not on for long periods. The flasher blinking rates might change a bit , could be a problem if they are flashing too fast.

    The lost 12V has to go somewhere, those commercial ( expensive ) voltage reducers would probably have heat sinks and other expensive components because the old incandescant bulbs .

  9. #9
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    While moving to LED lights might be good in theory. Who knows what trailer it might be pulling one day.

    Also there is the problem with electric brakes on trailers, they are 12V and some trailers have the controller on the trailer and need 12V to feed a battery.
    Gold, the colour of choice for the discerning person.

  10. #10
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    Apr 2008
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    NSW
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    There is no problem fitting led lights on any trailer . They draw less current than filament bulbs so the wiring loom is fine as it is . Done it several times .
    If you convert to 12 volt you could do it on the trailer after the socket . So 24V is still being switched in the truck to the socket but the power is reduced to 12V after the socket to run each light . Fit a sealed plastic project box to the drawbar and put the voltage reducers in that run the cables in and out of the box silicon up and Bob's your uncle . Will need some extra cable to refit to the plug . You could also fit an extra plug and lead into the box to go around the voltage reducers so the trailer can also be towed by a 12 V system . Mark the plugs 12V and 24V as required .
    Again 24V is no problem for the wiring because at 24v , and the same current draw , less wire gauge would be needed and it's only a short run . That way you could still pull another trailer with 24V lights .
    If a trailer had any kind of controller on the trailer with a battery charging wire that came off the socket then you just make sure the voltage reducer can handle the charging current draw .
    Or if the controller and battery required 24V then just run one 24v wire from the trucks socket direct to the device within the plug lead or add it to the outside of a cable using heat shrink over it .
    That way any 24V device gets 24V and the lights run on 12 Volt .
    The volume of a pizza of thickness 'a' and radius 'z' is given by pi z z a.

  11. #11
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    That can sometimes be correct but some lights give a voltage and nothing else so it's unwise to just hook them up and see what happens as you don't know what electronics may be inside the sealed package . If you are game to test one on 24 V then it may work ok but who knows how long it will work the extra voltage could reduce life span . It's like you can run a 12V winch on 24V but it don't last as long .
    Also the guarantee would be void if running them on an unapproved voltage and insurance could be risky if a fire started and they see the lights are running on unapproved voltage .
    Read the box and paperwork of the led lights and use the voltages they say . A 24 V system can get up to 36 volts when the engine starts .
    The volume of a pizza of thickness 'a' and radius 'z' is given by pi z z a.

  12. #12
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    Quote Originally Posted by .RC. View Post
    Would a few of those buck converters in a box work OK to convert the 24 to 12?
    I can't see why that wouldn't work - you may want to add a fifth converter for the reversing light, which some trailers have.

    One thing that might be a concern is the indicators - the settling time of the converter might cause a delay turning on, and also if there's low-current LED lamps on the particular trailer, the output capacitor might take a while to discharge, causing the indicator light to stay on longer - worst case it might not turn off before the next blink.

  13. #13
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    While saving a dollar is always good, there's often a reason why things are done a certain way.
    If you only tow one or two trailers than conversion to led lights would be the go, but if you may be towing multiple trailers than just bite the bullet and wire in something like this unit.
    https://www.ebay.com.au/itm/OEX-Volt...kAAOSwqYBWpbOV
    If you will be running electric brakes then this is what you need.
    https://www.redarc.com.au/electric-t...ake-controller
    Simple, reliable and industry standard.

  14. #14
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    Dec 2005
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    South Australia
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    redarc take that stance because you would be surprised how many customers expect they should replace items destroyed by the customer because the don't know what they are doing

  15. #15
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    Quote Originally Posted by .RC. View Post
    While moving to LED lights might be good in theory. Who knows what trailer it might be pulling one day.

    Also there is the problem with electric brakes on trailers, they are 12V and some trailers have the controller on the trailer and need 12V to feed a battery.
    Led lights on the trailer not the truck , convert the 24 to 12V on the trailer not the truck . Run an extra plug from the 12 volt side so a 12 volt vehicle can tow the trailer . The trucks stays at 24 volt so you can also hook up a 24 volt trailer .
    The volume of a pizza of thickness 'a' and radius 'z' is given by pi z z a.

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