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MCM2024 · 09-10-2024, 04:25 PM

We purchased a 2023 27' Int'l FB Twin with factory solar last year and have had it out on a number of trips where we've taxed the stock AGMs' capacity dry camping/boondocking.

I recently completed an upgrade to:
Deptech 300AH LiFePO4
Victron Smart Shunt
Bluetooth module added to the factory Victron MPPT 150/35

Everything went pretty smoothly. At the moment, I have the positive 10AWG cable into the 12v panel under the curbside twin bed wire nutted and electrical taped. I observed on the Smart Shunt that the LiFePO4 battery charges the TV when the TV is turned off and the 7 pin connector is connected, which I want to prevent, but still allow for charging to occur when the engine is running.

I purchased an Orion-TR 10A DC-DC charger to place in the middle of the 10AWG positive line coming to the 12v positive bus. What I'm stuck on is where to get the grounding wire for the chassis (which I will bridge across input/output as these are already tied at the 12v negative bus).

Does anyone know where the 12v negative bus is? It is not under the curbside twin bed where the inverter, MPPT, and 12v positive panel are located.

Thanks for any assistance!

I'm attaching a picture of the curbside bed compartment where the inverter, MPPT, and 12v positive panel are located.

-matt

jeffmc306 · 09-10-2024, 06:27 PM

MCM2024, have you removed the cover of the DC box inside the compartment under the bed?

Inside you’ll find a DC negative busbar with all the grounds connected. Otherwise, there’s another underneath the tongue of the A-frame.

Hope that helps!

MCM2024 · 09-10-2024, 08:24 PM

Thanks for the photo and response!

Unfortunately I didn’t take a picture of the physical components while I had the 12v panel box open. The box in my trailer does not have a 12v negative distribution bus within it.

While I didn’t take a picture of the wiring I did take a photo of the schematic on the underside of the cover. I’m attaching it and have outlined the part of the diagram corresponding to what’s in the box. It is all 12v positive wiring to the sole distribution bus and is accurate save for some of the wiring identified being on different posts than indicated.

Edit:
Anywhere else you think I should look to find the 12v negative bus bar?
^—— OOPS I missed your comment about there being a box under the tongue of the A-frame. Is it hard to run 10awg to it?

Thanks again for your reply!

jeffmc306 · 09-10-2024, 09:55 PM

MCM2024, the section you highlighted are the resettable circuit breakers on the 12 + busbar. See the right hand side of my photo to see it.

You might want to remove the cover from the DC box and take another look. Airstream hasn't changed their prewired DC boxes in a long time; I'd be surprised if you won't find the negative wires terminating on a busbar. By the way, the wires are probably white.

The ground bar under the tongue / along the frame isn't in a box - it's surface mounted. One of those bare copper wires goes into the DC box so either will serve your purpose.

Hope that helps!

uncle_bob · 09-11-2024, 09:19 AM

Quote:

Originally Posted by MCM2024

Thanks for the photo and response!

Unfortunately I didn’t take a picture of the physical components while I had the 12v panel box open. The box in my trailer does not have a 12v negative distribution bus within it.

While I didn’t take a picture of the wiring I did take a photo of the schematic on the underside of the cover. I’m attaching it and have outlined the part of the diagram corresponding to what’s in the box. It is all 12v positive wiring to the sole distribution bus and is accurate save for some of the wiring identified being on different posts than indicated.

Edit:
Anywhere else you think I should look to find the 12v negative bus bar?
^—— OOPS I missed your comment about there being a box under the tongue of the A-frame. Is it hard to run 10awg to it?

Thanks again for your reply!

Hi

Part of the "fun" of owning one of these trailers is spending a weekend with it in the driveway. You pop this open and look here. You pop that open and look there. You crawl around on the floor a bit. You do a bit of "un arranging" to the beds and seating. Anything that looks like an access panel, you take off.

For added fun, take a picture of what's inside each area and keep notes about what picture is from where.

Why do this?

AS changes the "what goes where" between models. They change it between years. They may even change it *during* the year.

Some things get put in (or maybe moved ... who knows) at the dealer. What they put where is up to them.

Net result is that each trailer is a bit unique. Also, if it's 3AM and there's an issue, it's a whole lot better to have some idea where to look than to start opening up everything and anything ....

Fun

Bob

MCM2024 · 09-11-2024, 06:08 PM

@jeffmc306 -- I'm certain there is no ground/12v negative distribution block within the panel, nor are there any breakers. The large block at the bottom of the diagram's highlighted area is literally a copper bar with two posts in each location to tie wiring to the bar. I'm kicking myself for not snapping a picture when I had it open to cap the 7 pin connector charge line. I'll hopefully be able to open it this weekend and get a picture to post. From what I could tell, all the white wiring exited the visible area toward the back of the trailer (bottom in the picture I posted of the compartment) or through small hole in the floor of the compartment.

@uncle_bob -- Yes! I had the trailer in the driveway a couple weeks while doing the upgrade and did get into a number of spaces I'd not been into before, including this compartment and the compartment with the WFCO converter. Unfortunately I didn't get pictures of everything I should. The trailer is now back in storage and I'll have to make a trip this weekend to take pictures of the interior of this 12v panel as well as try to chase down where the white wiring is headed as it exits the picture frame toward the back of the trailer.

Thanks both of you for the responses. I'll update with more pictures soon.

JandB · 09-22-2024, 11:51 AM

Looking at your photo; is this what you're looking for?

MCM2024 · 09-23-2024, 06:42 PM

@JandB Thanks for highlighting this! I looked at the picture again just before the weekend and spotted the same thing. Odd that it is mounted to the outside of the box. I had to remove the box to add a wire to the negative bus.

I'm nearly all done, just waiting for another chance to get by the trailer and install the charger.

JandB · 09-23-2024, 08:18 PM

Quote:

Originally Posted by MCM2024

@JandB Thanks for highlighting this! I looked at the picture again just before the weekend and spotted the same thing. Odd that it is mounted to the outside of the box. I had to remove the box to add a wire to the negative bus.

I'm nearly all done, just waiting for another chance to get by the trailer and install the charger.

Glad I could help.
I think many negative bars are outside the box.

I highly recommend you mount that solar controller (and your new charger) vertically as Victron recommends for proper heat dissipation. I have ours mounted on the aluminum wall with 3/4" #12 stainless screws.

MCM2024 · 09-24-2024, 06:38 PM

@JandB Good call on mounting the chargers vertically. It’s pretty disappointing the factory solar comes with the BlueSolar charger mounted out of compliance with its manufacturer’s instructions.

I made a small mount out of a scrap board and some L brackets which is mounted to the floor where the solar charger was mounted incorrectly. It will have the two chargers (BlueSolar and Orion Tr) on opposite sides. The BlueSolar is already mounted to it, I’ll be installing the Orion Tr soon and will get a final picture.

Thanks again!