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Reducing 24v to 12v

Vanman

Subscriber
Last Subscription Date
07/10/2019
Yep, that looks like the little do dad I was remembering. Seems perfect for this tiny load.
 

cobbadog

Registered
Thanks once again for the replies and great inofmation. I did just go with the single power wire from one of the batteries via a fuse to the memory wire for the radio and that is resolved and ready to fit new speakers and finish that job.
The teransformer I referred to is a heavy metal box bolted to the floor with 24v in 12v out and this is what powers the positive side of the radios mentioned and the lighter sockets for GPS and phone charging.
As for the trailer light plug it does have to be 12v as the trailer and caravan are also towed by the car which is 12v and is why I bought the heavy aluminium box about 12" long and 3" wide with all the seperate wire connections for indicators, brake, clearance and a power wire if required. It is this end of the truck where I was thinking of using a different way of reducing the power and it was just for the lights so the highest rated light was 21W @ 12v.
So it sounds as if there is no other way to resolve that area other than a line up of reducers for each light which would be a minimum of 4 reducers., plus an extra heavy one for a power wire if required.

The other thing is that they must be weather proof as well, just to make it even harder to resolve.
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Assuming that it is of sufficient capacity, you could run 12 volt power from the big converter in the cab to the back of the truck. Mount a weather proof box back there and put four single pole, single throw relays with 24 volt coils in it. One for brake lights, one for tail lights, and one each for left and right indicators. The truck’s circuits supply the respective relay coils, the 12 volt supplies each relay input, and each switched contact goes to the respective circuit on the trailer.

Keith
 

cornbinder89

Registered
Assuming that it is of sufficient capacity, you could run 12 volt power from the big converter in the cab to the back of the truck. Mount a weather proof box back there and put four single pole, single throw relays with 24 volt coils in it. One for brake lights, one for tail lights, and one each for left and right indicators. The truck’s circuits supply the respective relay coils, the 12 volt supplies each relay input, and each switched contact goes to the respective circuit on the trailer.

Keith
Yes that was what I suggested earlier.
 

pegasuspinto

Registered
the 'simple' and old fashion way was with a resistor, calculated to the ohms and watts needed for the load. It works fine for fixed, steady loads, like lamps, and/or loads where a couple volts give or take doesn't shut you down, like wiper motors. So you could use resistors for the trailer lights and be fine....UNLESS you switch trailers and it has any different lamp, and you take the risk that any circuit with multiple lamps might blow. (for instance, if you have ONE lamp on the brake light and it blows, OK. But if one lamp on the running lights blows, the voltage will go UP. That might blow another, voltage up. So on and so forth.)

Also, you might look into LED trailer lamps. They are versions that don't care if they are fed 12 or 24 volts. As long as you never 'accidentally' plug in a 12v trailer into your truck......but your trailer could plug into any truck.

IF you want to get rid of your old converter, there are TONS of ready built vehicle converters out there. Amazon has many for sale in 20-40 amps in a quick search, start here.... https://www.amazon.com/Power-Step-Down-Converter-Technology/dp/B003P17X8I

I would at least DOUBLE the amps when sizing the converter. Unfortunately, they are mostly chinese build and there is a bad habit of overstating the specs. (a 40A rated chinese style might melt down at 39.5 amps, lol.)
 

cobbadog

Registered
Yes, so far the box trailer is all LED lights and half of the van is also LED with the exception of the main lights across the back These are van specific in shape and not easy to match up the shape and bolt holes. The other choice I have for those lights is to install LED globes to handle that idea of being able to run them on either 12v or 24v which is probably going to be the best option if the multi point reducer for the trailer plug fails.
It seems to be a common problem around the rally fields with 24v truck and people buying 12v winches or towing their van for the weekend which is also a 12v set up.
 

pegasuspinto

Registered
For running a winch, your only simple options are matching the battery to the winch, or the winch to the battery. Converters are not practical at that amp load.
 
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