Home-Built trailer help (electrical more than metal)

Hi all, I'm just about finished building my utility coal-hauler trailer. (Metal content? about 300lbs. angle-iron and half an 8" spool MIG wire). Since this trailer has a GVW of 3500Lbs., brakes are required. I had trouble determining if a breakaway kit was needed, but all signs pointed to "yes". So if the hitch somehow falls off and the safety chains fail and I hit lotto and get struck by lightning, then the breakaway battery will supposedly energize the actuating magnets in the brakes. My question is this: if I were to attach everything to my 7-connector wiring connector on the back of the truck (one wire is for the electric brakes which are connected to a dash-mounted brake controller) would I fry said controller if I should happen to yank the lanyard out of the breakaway switch? Assuming that happened, the twelve volts from the breakaway battery would energize not only the brakes, but the 12v out from the brake controller itself. I know the manual says "don't wire this thing up wrong or you'll ruin it". I'm wondering if a diode between the controller and the breakaway unit would stop the current from flowing to the controller. If so, what kind? I have no clue about this sort of thing. Would the diode affect the operation of the controller? Any help would be much appreciated.

TIA, Nok

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direction, block voltage all together.

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Wire it exactly as the manual says and forget it. I am not sure what exactly you are concerned with, since the breakaway battery is connected to truck's 12v on a normal basis.

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It will IF they get triggered. You MUST provide a 'bomb-proof' (for the expected load of pulling that lanyard before failure) and totally independent anchor point for that break-away lanyard that won't get tangled up in the coupler. I put a 1/4" eye bolt through the body or the pickup bed near centerline and/or the license plate, with fender washer backups.

For a passenger car with a center license plate, you could use the eye bolt as one of the license plate bolts, too,

And make sure the hook on the vehicle end of that breakaway lanyard has a locking gate or bail, not an open S-hook that can fall off the anchor way too easily.

DO NOT clip the lanyard to the bumper hitch or the receiver hitch, because if the welds/bolts holding the hitch to the chassis fail, so does the lanyard anchor point. If the whole thing falls off (lousy welds...) the lanyard never trips - except by chance, getting snagged.

The standard way of wiring the break-away switch would backfeed to the car if tripped while still coupled - So what? The controllers should deal with it gracefully. If it only took that to blow it up, there is a serious design problem in the controller.

Don't try getting inventive with safety systems without doing some serious research - which you aren't getting over the internet, except to guide you to more definitive sources of information. There are too many people here that throw out guesses and conjecture without plainly labeling them as such, and not all of them get called on it.

You don't need diodes or any other mods not specifically authorized by the controller maker.


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Bruce L. Bergman


Very, Very, Very unlikely that the breakaway battery voltage would damage your brake controller.


Reply to
Carl Boyd

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