Thread: 24v to 12V electric brakes?

Yeah, I use the Voyager and like fiddling with the settings to suit varying road conditions.

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)

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

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.

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

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.

Originally Posted by soundman

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

Originally Posted by glenn k

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?

Originally Posted by glenn k

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.

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.

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

Originally Posted by glenn k

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. I can see why you'd be hesitant.

Originally Posted by glenn k

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.

Stepping off the draw bar onto the cable pulls them out easily.

Originally Posted by glenn k

Stepping off the draw bar onto the cable pulls them out easily.

I know... been there, done that.

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

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.

And that's exactly how Electric brakes work Buzza. 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.