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Electric brakes

justme
Explorer
Explorer
A vandal took my brake-away lanyard that energized my brakes to where the batteries ran down completely. Does anyone know if the brake magnets could be damaged for being energized until two batteries go dead over many hours? The brakes magnets are for Dexter 7,000 lb axels. The resistance reading is one ohm which may be ok with 4 magnets in parallel that are 4 ohms each. However, that does not rule out shorted windings. Does anyone have experience with this situation?
12 REPLIES 12

justme
Explorer
Explorer
Here is what the mfg says to my request: "It depends on the batteries powering the break away system. If the batteries are the standard small gel cells typically 5 to 7 amp hour capacity they are likely fine. The magnets would of pulled the batteries down in 15-30 minutes and while they would of gotten very hot they usually escape this unscathed. If you had larger deep cycle batteries on the circuit that typically power the living area when away from shore power it would of taken hours to kill the batteries and the heat for that length of time may have done some damage. A careful test drive will tell you the most. Even disassembly and visual inspection may not reveal any issues if the wire melted its varnish inside the magnet. I've included a direct link below on our magnet testing article incase you want to check them individually."

twopetes
Explorer
Explorer
My suspecion is if the magnets went bad, they would have burnt up and shorted out. You should be able to check for resistance thru the wires and if you do not have a dead short, they should be OK.

Have you checked the lead wires to the brakes? Are they burnt or bubbled? That would also give you an indication if the magnets overheated and are damaged.

Then that her for a drive. - I like the disconnect idea! I use it!

justme
Explorer
Explorer
Thanks for the input and advice. I did connect a spare magnet in free air to a battery and it got rally hot in ten minutes to where it could get damaged. If it was mounted in the drum I dson't know if it would get that hot. I did call Dexter and they could not guarantee it would survive and suggested that I have a reputable service check all the magnets out because partial melt down of the winding insulation would decrease breaking ability.

Gib3633
Explorer
Explorer
I had work done on my disc brake system and they pull the pin to energize the pump. By the time they were done there was a melt down in the brake a way switch itself. Of course they never mentioned that or maybe weren't aware but was kind of glad I checked it .
Moral of the story is see if you can pull the pin in you're bake a way switch.

Allworth
Explorer II
Explorer II
Why not call Dexter customer service and ask them? They know far more about Dexter equipment than anyone on here and the CS is great.
Formerly posting as "littleblackdog"
Martha, Allen, & Blackjack
2006 Chevy 3500 D/A LB SRW, RVND 7710
Previously: 2008 Titanium 30E35SA. Currently no trailer due to age & mobility problems. Very sad!
"Real Jeeps have round headlights"

path1
Explorer
Explorer
Hate to admit this...When we got our first trailer in the 90's, to prevent theft I disconnected the trailer and pulled the brake lanyard and stuck it in the glove box. I thought it would be a great way to prevent theft at our permanent lot. How smart would a theft have to be to bring along his own lanyard? Couple weekends later couldn't figure out why battery was dead. Plugged in lanyard, charged batteries and never a problem. Don't know if brakes have changed in 20 years?

That's was before the thought of water regulator, packing bearings, what type of tires or hitch ever came to mind. EPDM roof said good for 15 years, so why bother even looking at it. Maybe good old days?
2003 Majestic 23P... Northwest travel machine
2013 Arctic Fox 25W... Wife "doll house" for longer snowbird trips
2001 "The Mighty Dodge"... tow vehicle for "doll house"

Charley67
Explorer
Explorer
I absent mindedly pulled the breakaway cable to "make it more stable." A few hours later it hit me that those brakes weren't made for that. My battery was graveyard dead, but my brakes were okay. Hope yours will be, too.

attuco
Explorer
Explorer
I got mine caught once while disconnecting the camper. All four of the batteries discharged but no damsge to the brakes.

aruba5er
Explorer
Explorer
I'd worry more about the battery's. total discharge will ruin them. Another good example of having a disconnect switch on the battery. With one they would not be able to crank up the pin and drive away with your rv also. I think the coils should be ok, but then again, they where never very good at stopping anyway.

neal10a
Explorer
Explorer
I agree with Fulltimer50 and don't envy your situation. Theoretically speaking each magnet draws 3-4 amps which is 36-48 watts and could create a fair amount of heat over time. However, the magnets would pull to the drum which would be a good heat sink to dissipate much of that heat. However, the RV industry is not known for robust engineering that would design a magnet to survive continuous duty cycle in this situation. I could be possible that the insulation of the wire would break down and short a winding. That could allow the magnet to function and give the appearance of working but not at full capacity. Therefore the brakes would work, but not as good as they should. A check of each magnet with a ohm and current meter and compare the readings to a known good magnet would provide more confidence. Also check the coil resistance to it metal house to make certain the coils are not shorted to ground.

Fulltimer50
Explorer
Explorer
I dont see how it could cause any damage to the brakes. The mags get a lot hotter when in use than they could just being on. Only way to tell for sure is to repair/replace the switch, charge up the batteries and go for a ride.
George

2011 F350 PSD CC LB 4X4 DRW Lariate
2015 Mobile Suites 41RSSB4 5th Wheel

MFL
Nomad II
Nomad II
I have read that if you pull the plug, to test the brakes, that you should not do it for a long while. I'm not sure of what possible damage, maybe others will know.

Jerry