Emergency Brake Wiring

[epearce]

I'm wondering about best-practice for wiring the emergency brake on my MK200, now with two litium batteries, and a 30-A marine resetable breaker (I replaced that awful little two-post style fuse that is OEM)?

1. Directly to one of the two batteries?
2. To the battery side of the breaker?
3. To the load side of the breaker (no power to the brakes if the breaker is tripped, but batteries safe from a short)?
4. To the +12 distribution post on the frame

[howson]

epearce

For liability purposes, I'd wire the emergency brake switch exactly as it came from the factory. The controller (and brakes) won't care that the source of the DC is from a lithium vs the lead acid that likely came with your trailer.

The only concern -- regardless of battery type -- is the possibility of a scoundrel pulling the emergency brake actuator intentionally. I haven't read of an actual, verified instance of this happening but it would not surprise me. Unfortunately any modification to the system opens up all kinds of other potential "gotchas".

Just my .02. Others will probably have other thoughts.

Howard

[StephenO]

I'm wondering about best-practice for wiring the emergency brake on my MK200, now with two litium batteries, and a 30-A marine resetable breaker (I replaced that awful little two-post style fuse that is OEM)?

1. Directly to one of the two batteries?
2. To the battery side of the breaker?
3. To the load side of the breaker (no power to the brakes if the breaker is tripped, but batteries safe from a short)?
4. To the +12 distribution post on the frame

Eric, I'll second howson thought process that doing the wiring the same was as factory is best. For my trailer, that means your brake disconnect system is connected at the supply side of the self resetting breaker. While pretty much every DC circuit has an inline fuse to protect against a short, you wouldn't want a fuse on your brake wiring that could potentially stop your brakes from getting power. Especially if that fuse is somewhat hidden and blows without you knowing it. Could make a bad situation much, much, worse.

[epearce]

howson the two batteries was more in reference to the wiring. I had the old dual-lead acid system on an A/B/AB/off switch, so I had the brakes wired directly to one of the two batteries. Otherwise, if the switch were in the disconnect position, the brakes would not get power.
StephenO I replaced that little self-resetting breaker with a real 30-A marine breaker. Its disappointing that GD uses that part, then then abuse it as a distribution block. The posts on that were already undersized, and to try to pack every DC+ wire on the trailer under one of those two posts is not good practice. A breaker should be a breaker, and not serve double duty, especially one that small. I've seen several posts on other pages where people don't reallize that is not just a two-post distibution block.
Anyway, the brake is wired back directly to battery 1 again, no fuse. I suppose the wire on that run is small enough a short on the circuit will vaporize the wire before it hurts the battery.

[TucsonJim]

epearce - Eric,

From this photo, you can see how they used the breaker as a distribution buss on mine too.



BTW, they used the breaker on the left simply as a tie point to make a connection.

Here's how I cleaned it all up:



Jim

[epearce]

TucsonJim I did something very similar, and replaced the metal junction box with a 7-pin weathertight box. That also solved my intermitent turn signal problem as well.

[TucsonJim]

TucsonJim I did something very similar, and replaced the metal junction box with a 7-pin weathertight box. That also solved my intermitent turn signal problem as well.

We ought to go into the RV rewiring business...



Jim

[AlexPeterson]

Eric, I'll second howson thought process that doing the wiring the same was as factory is best. For my trailer, that means your brake disconnect system is connected at the supply side of the self resetting breaker. While pretty much every DC circuit has an inline fuse to protect against a short, you wouldn't want a fuse on your brake wiring that could potentially stop your brakes from getting power. Especially if that fuse is somewhat hidden and blows without you knowing it. Could make a bad situation much, much, worse.

My 2022 2500RL had an in-line fuse from the factory, just forward of the factory circuit breaker. I moved all that "distribution" junk from the frame up into the pass-through. The fuse for the disconnect brakes is also in the pass through now.

Putting in a 7-pin weatherproof distribution box is on my list for next year. Hard to believe GD put a 4" square metal junction box under there.

[Guest]

I'm wondering about best-practice for wiring the emergency brake on my MK200, now with two litium batteries, and a 30-A marine resetable breaker (I replaced that awful little two-post style fuse that is OEM)?

1. Directly to one of the two batteries?
2. To the battery side of the breaker?
3. To the load side of the breaker (no power to the brakes if the breaker is tripped, but batteries safe from a short)?
4. To the +12 distribution post on the frame

I struggled with this when my Lithium battery and charger were moved to the passthrough. I did not want a power feed inside the rig that was unprotected.
One solution is to install a dedicated brake away kit outside the rig. This would be a unit that has its own dedicated charger and 5ah battery. Power is direct between the small battery and the break away switch. The power feed to the unit could be protected from inside the rig.

Checking around I also gathered the acceptable method where the break away power feed can be connected to the battery through a dedicated breaker. No other circuits connected there.
What I finally did was to come up with a compromise to power the break away with a dedicated breaker inside the rig and through the main battery switch. Not officially acceptable but there is no possible way I would forget to turn the switch on for travel since the tongue jack and refrigerator is powered through the switch.

When the rig is stored, the battery switch is turned off killing all power except from the BMV-712. The eye of the break away cable is routed through the tongue pad lock. If someone removed the break away cable, I would be scrambling to find another in order to travel so its also secured.

Example break away kit.

https://www.amazon.com/dp/B07YD5Q2MV...1zcF9kZXRhaWwy

Jim

[epearce]

TucsonJim that 7-pin box looks just like mine! I just got my new solar controller in... still a moose-and-a-muffin story.

Now that I got the panel off, and about to route a right-sized pair of wires to support the 55 A converter charger back from the PDP, I'm considering just removing the OEM disconnect switch. I never use it, and have the 60A Type-III breaker that really does turn everything off but the emergency brake. Right now its just an extra lenght of undersized 12+ wire. Its pretty clear one side of the disconnect comes over from the battery, but where does the other side go? Is the disconenct really just disconnect the PDP 12+ input?

[howson]

epearce

While going to be different on your Transcend, the OEM battery shutoff will be wired similarly. Hopefully the diagram below helps.