24v to 12v trailer hitch converter

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Gotta do it right the first time...

G'day bloke,

Having been involved with a mixed fleet of 12V and 24V vehicles using the same trailers. I had arranged for the 24Volt vehicles to have Redarc 24/12 volt trailer convertors fitted (that did the tail, brake, indicators and Reversing lights). In Oz the current standard is a 7 pin connector (round or flat depending on local state custom) with provision for trailer brakes and separate reversing lights.
Note: in Oz we also have separate globes for brake and indicator although the tail light can "share" in the same globe but not circuit. This usually causes confusion when Oz vehicles are shipped over to the U.S. & Canada. When Trailers come over from The U.S the wiring and lights(couplings, brakes & even axels and wheels) are thrown away as they're not compliant with local regulations.

The issue with the trailer brakes is the proportional controller, I had a separate 10 Amp 24/12 convertor (switchmode one) to run the Tekonsha Brake controller, I used a 14V 5watt zener for the connection to the brake light switch and the ignition feed as these 2 circuits are low current draw. The zener drops the 24 volts to 12 volts, this method is only good for low currents as the zeners do get hot.

Electric trailer brakes are not just on or off, which is where the proportional controllers come into play. They modulate the current to the brake actuators in proportion to the the braking effort of the vehicle. If you run them off the brake light circuit the brakes will tend to lock up because they're being fed the maximum effort signal to the actuators. You may also pop the fuse for the brake light circuit.
 
ok, so I could run a set of relays to control the lights with 12v power coming from one converter and then get a second small converter to run the brakes with brake controller.

Is that about it? I can try and get a redarc converter but I hear they are a PITA to deal with from Canada.

Thanks.
 
Yes that sounds about right, you need to ensure the convertor you select for the trailer lights can cope with the expected load. That is all the tail, clearance, brake and indicators lights with at least 25% headroom. Just in case you have to tow a Xmas tree masquerading as a trailer. :santa:

Redarc are a local Oz product so I didn't have any supply problems.

Just check the maximum rated demand of the trailer brake unit and get a suitable sized convertor for that. Don't forget the 2 14Volt 5 watt zener diodes, Radio Shack or Newark/Farnell/Element 14 is where you'll get them.
 
I have a 24-12v solar converter that I used on an 24v HJ60 for hauling trailers. It's rated for 20amps, which I'm sure is enough for trailer lights and brakes. I no longer have the truck, but I kept the converter and would like to sell it. Interested? Send me a PM. I'm in Ontario.
 
I managed to talk burnaby hitch into building the logic circuit and installing a 7 pin plug (i'll only be using 4 pins for now). I've got a 35amp ICT converter that I'm installing to supply 12v power to the circuit. Thanks tho.
 
Tonight I built a quick pigtail converter to knock my 24volt down to 12. The premise I used was that two 12V loads in series would allow my trailer to run 12volt lights. The first load is a 12V LED wired into the 7 pin plug on each the left, right and brake lights feeder. This then plugs into the trailer plug. The second 12 volt load is the trailer lights. Both the trailer lights and LED are designed to drop 12volts so I'm hoping together they drop 24v. If the brightness of the trailer lights is any indication it all seem to be working fine. Time will tell..

I'm not sure my electrical theory is spot on but I hope it is. Don;t want to wreck my new LED tails....
 
A circuit diagram would help. It sound like one 12v lamp on the car and one on the trailer wired in series??
What happens when you take off the trailer, you would not have any tail lights on the car???


Also, series connections are frowned upon if you really get into the super safe “double redundancy" thing, because if one goes, the other one also stops working, unlike a parallel circuit.

If it's an LED and an incandescent in series then you incandescent probably wont light up because it will act as a current limiter to the LED. Best send a quick diagram as I may have it all wrong

Regards G
 
You may find the LED's may not survive very long.
LED's are a current not voltage driven device, your Indicator/Stop/ lights will be dragging excess current through the LED's. The Tail light may be ok as long as it's not more than 10 Watts.
If you had used equivalent globes to the various tail/ stop/ indicator that would have been better.
 
Came across this little beauty while searching for non dumping 24v to 12v converters..http://www.power-trax.de/produkte/electrics/electrics-e.htm
24volt to 12v trailer kit....webp
 
Diesel Cruiserman said:
Came across this little beauty while searching for non dumping 24v to 12v converters..http://www.power-trax.de/produkte/electrics/electrics-e.htmView attachment 936578
Click to expand...

Trailer supply directly off your wiring:
With this converter-regulator you may directly opertae any standard 12V trailer behind your 24V equipped vehicle.
This unit reduces the voltage for stoplights, foglights, flaher and taillight from "$V to 12V.
It is a fully electronic unit without any relais or large heatsink. Sophisticated semiconductor design enbables a smart design reducing the size of the unit down to a compact brick style.

  • Input: 24V (vehicle)
  • Output: 12V
  • power: 4x50 W (stoplight, taillight, foglight) + 2x21 W (flasher)
  • compact housing, no heatsink required
  • full electronic unit w/o solenoids
  • enclosed and sealed
  • Suitable forToyota Landcruiser, Trucks, Unimog, VW Iltis, utility vehicles a.s.o.
 
Looks to be a nice product.
I bought a similar unit from Australia about 4 years ago and it has proven very reliable.
 
That's a really nice unit. I built the trailer logic circuit myself and have a thread here somewhere with pictures I think. For a non-technical person like me, I'm pretty proud of it. Still working without problem all this while.
 
I use a standard Reese 24v unit for my BJ42 and didn't bother dropping the voltage down to 12v. My boat has LED tail lights, and LED tails are, from what I understand, generally rated for 36v. I've not had any issues and have driven at night with headlights on, etc. I carry spare 24v bulbs and spend the 5 minutes swapping them out if I tow something without LEDs. 24v Reese 4 pin harnesses are readily available where I am in Canada. I realize my setup probably isn't ideal for most, but hey- I daily drive a 32 year old Landcruiser.. I don't really care for creature comforts anyways, haha.
 
vanisle3b42, I ran that way for 20+ years with 24volts going to trailer output connector. However, during those years, I rented and towed several U-Haul trailers and burned out more than a few of their lamps. A few times I insisted when I rented the U-Hauls to switch out tail lamps to 24v ones. That worked fine. In a few other cases, they refused to allow me to switch them out and I was surprised that the 12v lamps could handle the 24volts -- for a short time. I always knew that I had to carry spares, so I managed to be safe. And more recently, they often have LED tall lamps and thus there are no issues. All that said, I am happy that I bought the converter so I never have to deal with those issues again!
 
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