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View Full Version : 24v to 12V electric brakes?



glenn k
22nd Jan 2010, 12:20 AM
I bought a 24 volt small truck and a 3.2 tonne machine to tow behind it. The truck has a round 7 pin plug (Vic Standard) but all the connections are reduced to 12V for trailers. This is all ok checked electric brakes worked but a bit grabby.
Checked and the stop lights and electric brake wires are both 12.1V so there is no electric brake control unit, which is why I couldn't find it, but the wiring is complicated with heat sinks all over the place.
Can I get a controler that will reduce 24V down to what ever the brakes need?
What do they need 5-12V?
Last unit I had just had a lever for manual over ride and a slide to adjust voltage so could I simply put a pot, or just a resistor, in the line and dile up the disired voltage and set and forget?
The trailer weight will never change, but heavier braking could be handy when needed.
Any suggestions?
I contacted Tekonsha via their web site and they suggested putting in a relay off the brake light wire to switch in 12V from one battery(in about 15 min).

damian
22nd Jan 2010, 08:45 AM
The problem with a pot or resistor is you have to dissipate heat. Although the voltage drop is small the amps are large.

It's entirely doable but if you don't do it correctly it'll fail and murphy dictates it'll fail at the worst time.

If you can take a feed from one 12V battery that's a much nicer solution. Maybe a switch and a diode to pull in the extra 12V as required...

Yonnee
22nd Jan 2010, 10:08 AM
I've done this before, either one of two ways. The more expensive but correct way is to have a 24 - 12V reducer. These are used to fit 12V radios, run 12V lights, etc. on 24V vehicles. You'll need one with enough capacity to run everything that's connected to it, including your controller and magnets (12 Amps for 4 wheeled brakes at full lock). These reducers can have several cicuits for running all the different lights on the trailer, and the brake light circuit is used to trigger the Brake controller unit (this means running an extra wire from front to rear).
The other way to fit the controller is to tap into the positive terminal of the battery that is connected to Earth/Ground on the truck. Sounds simple enough, but you also require a 12V feed to the brake light trigger for the controller. This is what Tekonsha were refering to with a relay. Some will urgue that's it's not good for the batteries to have one being drained more than the other, but the drain is fairly miniscule and is not constant. If it is a concern, swap the batteries every three to six months so that each one has a turn at being the 'Earth' battery.

Last unit I had just had a lever for manual over ride and a slide to adjust voltageI'm going to have stab and say it was a Hayman Reece controller? I can't think of any that only has the one adjustment. There is a timer delay adjustment on the H/R, but not many know it's there or use it.
Don't get me started... they should stick to what they do very well, and that's making towbars.

dazzler
22nd Jan 2010, 08:08 PM
Redarc make a 24v to 12v reducer that is wired ready for the Tekonsha Voyager. Had this on my Hino and it was good.

glenn k
22nd Jan 2010, 09:06 PM
Bought a GSL electronic Brake controler they make them in 12 and 24V. The 24V has only been out about 8 months sounds much the same as a Tekonsha but made in Australia.
Thanks for the posts everyone.

Yonnee
23rd Jan 2010, 12:58 AM
Bought a GSL electronic Brake controler they make them in 12 and 24V. Oh dear God no... :C


The 24V has only been out about 8 months sounds much the same as a Tekonsha but made in Australia.
Thanks for the posts everyone.
I'm sorry to burst your bubble glenn, and the following is not personally directed at you, so I hope you don't take offence.

From what I read on their website, they are definately not the same as Tekonsha. The only similarity is the words "Brake" and "Controller" in their titles, and only one of them actually should be called a Brake Controller. The Tekonsha units are all controlled by an accelerometer, which detects how hard you're braking and varies the output to the trailers brakes accordingly. The other is purely a time based variable voltage output device, is downright dangerous for inexperienced tow drivers, and will void any warranty offered by the Axle manufacturers on their brakes.

I wonder if it could be proven if a fatal accident was caused by one of these timer based "controllers", and if it could, would they be then removed from the market?

glenn k
23rd Jan 2010, 12:06 PM
Thanks Yonnee I was reading that Tekonsha units are all controlled by an accelerometer I thought the GSL was aswell (as they say new generation of brake controlers utilising microprocesser based technology which is true) but as you say they only mention variable time delay.

Kyle
23rd Jan 2010, 11:14 PM
Go for the Tekonsha with the Redarc 24v to 12v reducer.

The Redarc brake controllers are pretty good quality, but are old technology.

I picked up a Tekonsha Primus IQ proportional controller on Ebay for $100 delivered before Xmas.

glenn k
24th Jan 2010, 02:03 PM
I have installed the 24V GSL unit it works much better than having 12V going straight to the trailer, but it does seem to be on or off and it resets everytime the truck starts up. I have sent an email to the manufacturer to see if this is correct.
While installing it I found a wire tapping one battery used for something else so I used this to make a 12V cigarette lighter for my GPS and there is a solinoid at the rear of the truck that switches 12V when the brake is applied so with 6m of wire I could run a 12V system,Tekonsha or what ever.

Is a Tekonsha that much better?

Kyle
25th Jan 2010, 12:28 AM
Is a Tekonsha that much better?

I can't comment personally, as the Tekonsha is the first brake controller I've owned and used.

I purchased a Redarc controller originally at the recommendation of my mechanic mate and his auto elec, but changed my mind the day before I was going to install it and decided I would be better off with a proportional controller.

With the old type controllers the trailer will only brake as hard as the voltage it's been preset at. With a proportional controller the trailers brakes will match the brake force of the tow car.

Check out all the caravan and camper trailer forums and the overwhelming majority of people recommend the Tekonsha. Most of these people have use all types of controllers over the years.

Yonnee
25th Jan 2010, 08:17 AM
Is a Tekonsha that much better?

When I was running Melbourne Trailer's Repair & Service Centre, the amount of times I had customers come in with what they think is a braking problem with the Caravan, only to find the controller was from the people who should stick to making towbars. So we hooked their Caravan up to our company car with either a Tekonsha or Dexter controller, and they'd asked to have it changed on the spot. Some went to ask for their money back from where they'd bought it from, others just threw it in the bin on the way out.

The biggest issue, is that "Solid State", or "Microprocessor Controlled", or whatever fancy name they give it for "no moving parts" Controllers, have absolutely no way of telling how hard you're braking. They know no difference between a light braking application to gradually slow to an intersection, anticipating a light change, or a moderate aapplication because you missed the light change, or a severe application because a child ran out chasing a ball. You also have no way of adjusting a timer based controller for wet or gravel roads either.

With the right controller, you shouldn't have to change your braking habits to suit the controller.

glenn k
25th Jan 2010, 11:32 AM
Thanks Kyle and Yonnee (love that name) for your comments. I can turn the braking up and down with the push of a button and it has a lever for full power so it is much better than a trailer mounted option. I'm getting the truck and trailer registered on Wednesday so I didn't want locking trailer brakes while I was backing over VICROADS pit. So I needed something quick. I will then try it out for a while and see how it goes for real. If I go for a new unit what would you suggest as the best model? The truck has a gross weight of 5.2 net 3.2 and the trailer is 3.2 but it doesn't carry anything as a load. I'm only 200Kg below the maximin towing capacity of the truck.

rsser
25th Jan 2010, 12:46 PM
Maybe look at the Tekonsha Voyager, a manual unit, which IIRC is adjustable both for trailer braking delay and strength.

Kyle
25th Jan 2010, 04:07 PM
I picked up the Tekonsha Primus IQ on Ebay for $100 delivered. This is a proportional controller with 3 adjustable boost settings for heavier loads. It does up to 3 axles, but doesn't work on electric/hydraulic brakes. The Tekonsha P3 is around $180, has the same features as the IQ but uses a more comprehensive LCD readout, can do up to 4 axles and electric/hydraulic brakes.

The IQ is fine for my Pajero and 1400kg caravan, but the P3 maybe better suited for your truck.

glenn k
25th Jan 2010, 04:21 PM
Should have mentioned trailer only has 1 axel 9.00x17.5 tyres probably 12" brake drums with straight electric brakes. So it may not need a larger unit.

soundman
27th Jan 2010, 09:21 AM
There are quite a few good quality voltage reducers out there......running you brake controller off one of those is a good choice..... but buy a good one buy an adequate one.

running off a 12 volt tap from your 24 volt battery bank......in this situation.. probaly isn't going to cause the batteries any problem... because the drain from the brakes will be small if considered over time...and the batteries should easily equalise such a small ammount... but there will need to be a relay in your brake light circuit yess.

Neirther of the above choices I would consider bad choices.

As for getting a proper enertia operated proportional brake controller......absolutely no question.....anything else is a very poor choice... and the bigger the trailer the worse the choice.

Properly set up electric brakes are a great blessing.......I am constantly ammazed about people cutting corners on electric brakes.

even the simple tekonsha voyager, will do a great job on a straight forward braking system.. and they are not expenive.

cheers

rsser
27th Jan 2010, 11:01 AM
Yeah, I use the Voyager and like fiddling with the settings to suit varying road conditions.

glenn k
29th Jan 2010, 11:09 PM
Bought one of these Primus IQ's on Ebay $106 delivered as the CSL controler is far too jerky unless I wait to the last second and brake hard.
In the Primus IQ instructions it says:
Disconect trailer plug from
tow vehicle prior to testing
a breakaway switch or you may
destroy the brake control.
Does this mean if someone steps on the breakaway cable and pulls it out, or if the trailer comes off the ball, the brake control is destroyed? If so very poor design. Can a diode be added to stop this if so what would anyone recommend? I'm concerned that the extra resistance will reduce braking power (I suppose it can just be turned up)

soundman
30th Jan 2010, 08:13 PM
WOT......So if the breakaway switch operates you might blow up the controller.

Sounds like who ever designed the controller, did not design the output stage of the controller properly.

I recon that because the controller can not withstand events that could be considered a normal part of operation...namely operating the breakaway feature for the purpose of testing... the item could be argued as not fit for purpose.

cheers

glenn k
30th Jan 2010, 10:14 PM
Yes I agree Soundman. The breakaway switch is not an if it's a when. Standing on the draw bar is an everyday thing to do to get into the back of the truck so standing on the breakaway cable is a very likely thing to happen.
The unit has no protection, connect the power leads up the wrong way and it's destroyed. The GSL had protection against these things built in maybe Tekonsha want to sell lots of replacement units.

soundman
31st Jan 2010, 12:25 PM
not knowing the configuration of the output stage.. or in fact the reason for the problem... I could not say for sure.

But typicaly on power output stages the series diodes, reverse biased doides, transorbs or similar would be considered normal particularly when the device is driving inductive loads.

Why a device like this would have a problem with a foreign battery being connected to a line ( that is what the breakaway system will do) I am just baffled.......

cheers

glenn k
2nd Feb 2010, 08:07 AM
I asked Tekonsha about this and was sent this
"The way the breakaway system could destroy the brake controls would be if the breakaway battery was wired backwards, with the positive terminal of the battery going to ground and the negative terminal connected to the electric brake wire. If the breakaway battery is wired correctly, pulling the pin on the breakaway switch will not harm the controls."
So I will now wire it up as there is not a problem.

Yonnee
2nd Feb 2010, 07:56 PM
I recon that because the controller can not withstand events that could be considered a normal part of operation...namely operating the breakaway feature for the purpose of testing... the item could be argued as not fit for purpose.

cheers


Yes I agree Soundman. The breakaway switch is not an if it's a when. Standing on the draw bar is an everyday thing to do to get into the back of the truck so standing on the breakaway cable is a very likely thing to happen.

Well I actually don't agree.
The testing feature that is fitted to Break safe units does not require it to be plugged into the tow vehicle. It is even stated in the instructions that it is not to be tested by pulling the break away switch.

The idea of the break away is to apply the trailer brakes in the event you lose all control of a run away trailer. In other words, there is more to hooking up your trailer to your tow vehicle than just hitching up the coupling, and connecting your chain and wiring. With a break-away system on your trailer, the chain should have enough length to allow the towing rig to turn or reverse without binding up, but, where possible, short enough to not allow it to reach the ground should it come off the towball. Your wiring plug should then be long enough to still be plugged in at full stretch of the safety chain, as this will allow you to apply the over-ride to still have some control over your decellaration. And then the break away cable should just be just longer than the wiring plug, so that if the chain or its attachments break, then the now separated trailer will apply its own brakes at full lock. The break away cable should also be attached separately to the tow vehicle rather than the same 'D' shackle as the chains, because if it is the 'D' shacle that lets go... what's going to pull the breakaway switch out?:o



I asked Tekonsha about this and was sent this
"The way the breakaway system could destroy the brake controls would be if the breakaway battery was wired backwards, with the positive terminal of the battery going to ground and the negative terminal connected to the electric brake wire. If the breakaway battery is wired correctly, pulling the pin on the breakaway switch will not harm the controls."
So I will now wire it up as there is not a problem.

I was going to comment on this earlier, however your question has been answered by Tekonsha.
The magnets themselves will work either way, irrespective of polarity, but Tekonsha probably had to deal with one warranty claim by a 'nuff-nuff', that they now put this warning on all of their installation instructions for all of their models. And as the cheap way of having a break-away is a car battery in a box and a sub $50 switch without colour coded wiring, you see how easily it could be hooked up wrong, and still work, but destroying the controller.

glenn k
2nd Feb 2010, 10:53 PM
Thanks for the trailer hook up info Yoni. But can you see why I didn't want to connect the unit up before they explained the polarity thing? The breakaway is sure to be pulled out by mistake on day and bang no breaks. But this is not the case so all is fine.
I wisk they had left this out of the instrutions or explained a bit better.

soundman
2nd Feb 2010, 11:34 PM
If you don't pull the breakaway plug... you are not testing the operation of the full breakaway system.......the breakaway switch would be an expected point of failure.....testing this would be a wise thing......and any electronoics designer with any sort of foresight will expect the breakaway switch to be operated either to test or by accident at least some time in its life.

As for reverse polarity.........I am constantly amazed that designers of automotive devices do not consider this as a probable outcome at some time.... everybody connects something reverse polarity at least once.

Surely a proper warning that the breakaway system should be installed with its battery the right polarity..... would be a far more appropriate warning.
If the breakaway battery is installed incorrect polarity... there is a very big liklyhood of other damage to the charging system, if the system isn't properly fused......if the craging system is properly fused and the fuse blows there is a very good likelyhood that the breakaway battery will not be charged and the breakaway system will not work.

All still very sus.

proper fusing, proper electronic design...and especilay proper installation....... none of this should ever be a problem.

This is just another example of cheap crappy trailer components

cheers

Yonnee
3rd Feb 2010, 01:39 PM
Thanks for the trailer hook up info Yoni. But can you see why I didn't want to connect the unit up before they explained the polarity thing?
No worries. :2tsup: I can see why you'd be hesitant.


The breakaway is sure to be pulled out by mistake on day and bang no breaks. But this is not the case so all is fine.
I wisk they had left this out of the instrutions or explained a bit better.
Maybe their warning should better explain it... but then again, it's just easier for them to cover themselves and warn against it full stop. As I explained earlier, a break away system can legally be homemade, so rather than going to the extra expense of making their product absolutely idiot proof, it's cheaper to print "dont do it". Besides, if it is hooked up correctly, it's not an issue, and Tekonsha probably didn't see the need to point it out.

As for the break away switch being pulled out by mistake, they're pretty eff'n tight. They're done that way so as not to vibrate loose. I've seen some worn so much from being pulled apart so many times that they don't stay in any more.:no:

glenn k
3rd Feb 2010, 07:20 PM
Stepping off the draw bar onto the cable pulls them out easily.

Yonnee
4th Feb 2010, 04:56 PM
Stepping off the draw bar onto the cable pulls them out easily.

I know... been there, done that.:doh:

I'm not saying it doesn't happen, it's just not ideal for the switch's longevity.

Buzza
7th Feb 2010, 10:55 PM
As an old truckie, I can only say I want my trailer brakes to act just as the prime mover brakes work. They should pull on at the same rate as the tow vehicle.

When I drove my first semi-trailers, they had vacumn brakes on the trailer, and a hand piece to be used by hand at all times up front to operate them. These were phazed out in the early seventies, as they were "Widow Makerrs". They could take nearly two seconds to act on the trailer wheels. By then, the whole rig was probably well into "Jack-knife mode". Coming down hills and mountain sides, these trailer brakes were used independantly of the prime mover, and therfore, some drivers would over heat the trailer brakes, setting the linings afire, and then the whole rig took off as the prime mover brakes couldn't hold the lot back anymore. The next system was all powered from compressed air.

I'd go for the one that does not need a "FREE HAND" to do anything at all whilst driving.

Yonnee
7th Feb 2010, 11:19 PM
And that's exactly how Electric brakes work Buzza.:2tsup: The correct controller, properly adjusted, will apply power to the magnets as soon as your brake lights trigger the unit, and will automatically adjust that power depending on your braking inertia.

The only time you need a free hand is if you ever feel the need to use the over-ride control fitted to all Electric Brake Controllers.

Buzza
7th Feb 2010, 11:35 PM
Well the only good thing about them, was the ability to "hold" the vehicle at a stop sign situated on an inclined road. That way, you could find your take off gear and release the clutch to take up the drive and release the hand piece. I guess you can do that with these electric brakes.

I notice a lot of caravans and boats for sale that would need these fitted. Could be an expensive trap for young players. :oo:

Yonnee
7th Feb 2010, 11:52 PM
Well the only good thing about them, was the ability to "hold" the vehicle at a stop sign situated on an inclined road. That way, you could find your take off gear and release the clutch to take up the drive and release the hand piece. I guess you can do that with these electric brakes.
PBR used to do a vaccum system for caravans in the early days. Worked pretty much as your old vaccum truck brakes, just on a smaller scale. But seeing as most passenger cars don't run compressed air for their braking system, it would be an extremely expensive option to install an air brake system. Although, there is an of the shelf system you can get for the trailer.


I notice a lot of caravans and boats for sale that would need these fitted. Could be an expensive trap for young players. :oo:
I'm guessing you mean Electric brakes and controllers, instead of the over-ride hydraulic brakes? They can be a little pricey to retrofit from scratch... ball park, around $500 plus installation, for both the trailer and the tow vehicle.