Explain how emergency trailer brake gets power?

ewarnerusa wrote:
To clarify, I confirmed that the brakes are wired to operate off of the trailer battery. But the trailer does not have a separate battery dedicated to brakes.
In a previous job I drove a work truck hauling an equipment trailer and that trailer had a small battery on the tongue that was only for the emergency brake system.

Yes, you are correct. Equipment trailers, cargo trailers, any trailer with brakes has to have a means of applying the brakes in the event of a disconnection from the tow vehicle. Each state in the US may differ on the weight rating, here in OH it is anything over 2,000 # must have brakes. Even hydraulic surge brakes have a setup to create an emergency break away with a chain or cable that pulls on the coupler which pulls on the master cylinder.

Since campers have an on board battery for 12 VDC items on the tongue or close to it, that battery serves as the brake emergency power. Equipment trailers or other trailers with no other need for a battery, those have the separate little mini battery. If I recall correct, the size of the battery, has to be able to hold enough power to support full braking for 15 minutes.

Also to note, if your camper has a battery disconnect, the breakaway power should be tied in upstream of the disconnect, not down stream. The breakaway power has to be live all the time. Many campers only have one large wire to the battery, and if it has the disconnect, they tap in on the upstream lug of the disconnect so you will not see a separate little black wire to the battery just for the breakaway power.

And while we are on this topic, many breakaway switch manufactures recommend their "standard" switch be changed, every 3 to 5 years. Look up yours, I'm sure it's in there instructions. Some picked 3, some 5. The issue is, water can get in, corrodes things and then the switch will freeze up or not pass full current due to the corrosion, then burn up in some cases. This switch is a much forgotten safety item. You should pull it to check at least once a year that the O ring has not swelled, dried up , cracked and can leak and then sometimes the pin won't come out. Spraying with liquid silicone on the O ring once a year to helps for that. Anyone buying a used camper over 3 to 5 year old most likely has the original switch on it. And this really does not change much if the camper is 10 or 20 years old etc. It just gets forgotten. Some states require trailer inspection and that inspection will catch some of the non working switches, but some state have no trailer inspection, you will get a ticket if stopped and not in full compliance.

Have fun with your new camper.

John

ewarnerusa wrote:
To clarify, I confirmed that the brakes are wired to operate off of the trailer battery. But the trailer does not have a separate battery dedicated to brakes.
In a previous job I drove a work truck hauling an equipment trailer and that trailer had a small battery on the tongue that was only for the emergency brake system.

Yep. In trailers with electric brakes that are not RV’s there is a separate battery. It is the law here on trailers with electric brakes that are over 1400 kilograms.

To clarify, I confirmed that the brakes are wired to operate off of the trailer battery. But the trailer does not have a separate battery dedicated to brakes.
In a previous job I drove a work truck hauling an equipment trailer and that trailer had a small battery on the tongue that was only for the emergency brake system.

toedtoes wrote:
My trailer has both a house battery and a hitch battery (to power the hitch jack). The trailer brakes are connected to the hitch battery.

That is actually the law here in BC. And the MOT guys check it on their highway spot checks. If your trailer has electric brakes it is required to have a battery.

My trailer has both a house battery and a hitch battery (to power the hitch jack). The trailer brakes are connected to the hitch battery.

Okay I was able to confirm that the two wires going into the side of the junction box along with the main 12 volt do come from the breakaway switch controller. When I pull the pin from the breakaway switch, I observe about a 7 amp draw on the batteries. So things seem to be working as designed.

BurbMan wrote:
That connection is inside the junction box where your 7-pin cord terminates at the trailer. The breakaway switch is wired to both 12v positive from the TT battery and the blue brake wire.

Thank you, this seems to correspond with what I'm remembering and what is in the picture. I'm pretty sure the 7-pin cord comes into the bottom of that junction box where the sun-baked red 12V wire from the circuit breaker is entering from the side. One or both of the other small gauge wires are coming from the back of the breakaway pin box if memory serves. I'm trying to remember all of this as I sit in the office and the camper is at home. I'll go check some things out when I'm hom.

Best way to test it is to hook up as per normal. Then disconnect your 7 pin, pull the emergency tether and then roll forward. If you are dragging your wheels you are good to go. Don’t forget to reinsert the thingy. We do this every 6 or 7 hookups...just in case. :)

That connection is inside the junction box where your 7-pin cord terminates at the trailer. The breakaway switch is wired to both 12v positive from the TT battery and the blue brake wire.

I bought the camper new from dealer and the only rewiring would have been by me. I'll have to do some testing to see what happens. If I remember right, the wire from the back of the breakaway switch went back into the junction box on the frame where the main 12V supply to converter/power center.
I found a photo I took for another purpose which I've zoomed in and cropped down.
I think the gray wire(s) are from the breakaway switch.