DC-DC charger and Emergency Breakaway

[Country Campers]

An owner brought this up to me today and I thought I would pass it on to the masses.

The issue is with the DC-DC charger that uses the stock wiring from the tow vehicle thru the 7- wire connections.

What we have found is with the factory wiring in a fifth wheel , not sure about a TT.

From the factory the charge wire from the tow vehicle is connected to the emergency breakaway switch and also to the charge wire going to the bus bar inside the front storage and then to the battery to provide charge while towing. The problem is when the DC-DC is introduced into the system the charge wire from the 7 wire is removed from the bus bar and attached to the input of the DC-DC charger. WIth this being done and the DC-DC is wired so that it is only on when the owner switches it on or when the tow vehicle is attached there is no power to the emergency breakaway unless the tow vehicle is attached to the RV. If I understand the DC-DC correctly it will only pass power thru from the input side to the output side and not the reverse. In that manner if the 7 wire becomes unplugged from the tow vehicle there is no power to the emergency breakaway switch, which could happen in the emergency that it is designed for. So to remedy this issue we will need to run a new wire from the battery positive to the emergency breakaway switch so that there is always battery power there as it is intended.

I am open to other suggestions if there are any but I can not think of any other way to fix the problem.

Just a heads up to all of the owners that have done this modification. The emergency breakaway needs to function in the manner that it was designed for, safety counts.


Brian

[ncitro]

Interesting. I left my factory charge wire in place when I did my install, I guess that's why I've never had an issue. I've definitely tested my breakaway when disconnected from the truck before.

[Yoda]

An owner brought this up to me today and I thought I would pass it on to the masses.

The issue is with the DC-DC charger that uses the stock wiring from the tow vehicle thru the 7- wire connections.

What we have found is with the factory wiring in a fifth wheel , not sure about a TT.

From the factory the charge wire from the tow vehicle is connected to the emergency breakaway switch and also to the charge wire going to the bus bar inside the front storage and then to the battery to provide charge while towing. The problem is when the DC-DC is introduced into the system the charge wire from the 7 wire is removed from the bus bar and attached to the input of the DC-DC charger. WIth this being done and the DC-DC is wired so that it is only on when the owner switches it on or when the tow vehicle is attached there is no power to the emergency breakaway unless the tow vehicle is attached to the RV. If I understand the DC-DC correctly it will only pass power thru from the input side to the output side and not the reverse. In that manner if the 7 wire becomes unplugged from the tow vehicle there is no power to the emergency breakaway switch, which could happen in the emergency that it is designed for. So to remedy this issue we will need to run a new wire from the battery positive to the emergency breakaway switch so that there is always battery power there as it is intended.

I am open to other suggestions if there are any but I can not think of any other way to fix the problem.

Just a heads up to all of the owners that have done this modification. The emergency breakaway needs to function in the manner that it was designed for, safety counts.


Brian

Brian
A brain basher this is - the solution simple it may be. OK OK Why cant you wire the breakaway switch directly to the battery bus bar (no connection to the TV charge wire)? Then the TV wire only goes to the DC-DC converter that charges the battery. If there is a disconnect it takes power directly from the battery. DC-DC charger is totally isolated this way.

Hopefully the Force has not lead me astray in this thinking.

Keith

[KSC_Travels]

Something amiss here in the logic I think - or I am not understanding. It would be impossible for any vehicle to provide power to the brakes once it is disconnected. The brakes (in a breakaway activation) must receive power through the breakaway switch from the RV battery - no other source of power. So - moving the 7-pin charge wire should not affect this circuit

Easy enough to check - just pull the breakaway pin when the RV is disconnected from the vehicle (don't leave it out very long).

[Jlawles2]

KSC_Travels The issue is how GD routes the wires. The break away on 5ers is setup such that the TV 12V+, Break Away, and Charge wire to the battery are all tied together in the metal box. Thus breaking the connection from the TV charge wire to the battery and putting the DC_DC charger inline creates the issue. The DC_DC charger will not back feed the circuit.

More appropriate way to power the DC_DC would require a new wire to the battery or the charger to be in the pin box.

[KSC_Travels]

KSC_Travels The issue is how GD routes the wires. The break away on 5ers is setup such that the TV 12V+, Break Away, and Charge wire to the battery are all tied together in the metal box. Thus breaking the connection from the TV charge wire to the battery and putting the DC_DC charger inline creates the issue. The DC_DC charger will not back feed the circuit.

More appropriate way to power the DC_DC would require a new wire to the battery or the charger to be in the pin box.

Jospeh - that's Interesting... but still not making sense to me. This pic was posted in another thread (IIRC it was from a 303) and clearly shows the RV 12V+ connected directly to the breakaway switch power at the bus bar. Nothing to do with the 7-pin wiring or junction box on the pin box.

EDIT - Unless you're saying that that breakaway wire goes back through the pin box junction and is somehow interrupted in there (which wouldn't make sense to me but... anything's possible with RV wiring!). But I "think" that wire goes directly to the breakaway switch mounted on the pin box. I will have to check that next time I visit the rig in storage.

[KSC_Travels]

But I should add - just because a diagram shows this doesn't mean it's necessarily true . A visual inspection and/or a simple test (by pulling the breakaway pin) when disconnected from the tow vehicle would be advised.

[Scott'n'Wendy]

Seems to me that when you add the DC-DC, you move the charge wire from the bus to the DC-DC, then back to the bus, but leave the breakaway switch wire on the bus, in it's original position..which is connected to the battery, so the brakes work fine.
Like KSC, I don't see the issue if you leave the breakaway sw. wire on the +ve bus.

[Jlawles2]

I think it depends on the age of the unit. I do not remember if mine is setup with the breakaway to the bus bar or the whip. I'll have to look and see. I believe on my previous TT and 5er it was whip, charge wire and break away all combined.

[Yoda]

KSC_Travels Scott'n'Wendy Jlawles2 Country Campers

What Joseph and Brian are trying to say (and it is how mine is wired) is the TV 12+ charger wire comes to the king pin junction box. Inside that box is a 3 way junction on that line. They (GD) used a bulb connector to tie 3 black wires wires together.( A picture of this was posted somewhere in a post asking what/where the third black wire went to)

One is from the TV (7 pin cable), One goes to the break away switch that is mounted to the side of the king pin box, and one goes to charge the battery (connected to the hot side of buss bar). GD saved money on several feet of wire length doing this and for the stock unit is very correct. The breakaway switch is not wired directly to the buss separately, just T'ed into that power line. As is, it will work if the break away switch is activated as power from the battery is available if the 7 pin plug disconnects.

If you put a DC to DC charger in line with the one wire that goes to the battery, you loose the power in case the TV is disconnected as the DC-DC charger will not allow reverse flow back to the T. So somehow constant power is needed to the break away switch.

My suggestion is to remove the splice and take the disconnect switch power directly to the battery - run a new line. Then the DC-DC can be installed on the original charge line and work as intended.

Now on my DC-DC install I ran a separate line for the DC-DC unit, so the T connection can remain in my case. Hopefully this is clear as mud now.


Keith

[Scott'n'Wendy]

Yoda
Ah...ok..I thought the wire that is electrically tied to the breakaway had no joints in it between battery and switch. IMO..it shouldn't be spliced in another location when it is a brake safety device...but you know what they say about opinions...lol

Thanks for the expanded explanation.

[KSC_Travels]

Yoda
Ah...ok..I thought the wire that is electrically tied to the breakaway had no joints in it between battery and switch. IMO..it shouldn't be spliced in another location when it is a brake safety device...but you know what they say about opinions...lol

Thanks for the expanded explanation.

Yes thanks Yoda

My sentiments too Scott. As Jlawles2 noted - maybe it's build year related. Dunno - but now I'm really curious... time for a trip to storage now that it has warmed up to -7 C today

Ken

[TucsonJim]

The break-away circuit on my 2017 reflection 297RSTS is wired directly to the battery. So travel trailers may be different than the fifth wheels.

Jim

[Guest]

The break-away circuit on my 2017 reflection 297RSTS is wired directly to the battery. So travel trailers may be different than the fifth wheels.

Jim

Jim,

Our Imagine break away switch was also wired directly to the battery via the frame mounted circuit breaker as a junction. The switch was connected to the battery side of the breaker.

Jim

[epearce]

My emergency brake power even comes up from the other side of the TT by the shortest path, and hooks directly to the +12 terminal on battery 1. No connections, no fuses. Big oversized 10 AWG wire.