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?

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

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.

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.

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.

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

Electric brakes | Good Sam Community

twopetes
Explorer
Nov 05, 2015
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
Nov 06, 2015
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."

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