Please Check: Ready to Start Building this Design

EricR

New Member
LIABILITY RELEASE: I hereby release anyone and everyone from any and all liability related to advice given in response to this request for help. Including all replies, replies to replies, replies to my follow-up replies, etc.

Hello,

Sorry this is a cross-post. This was posted in the Safety Check section but no one has replied.

Please review and comment on this. All of my parts are in and I would really like to get started this weekend.

All help is greatly appreciated!

We have a Lance 2185 travel trailer that I am going to upgrade from FLA to LFP. At the same time I will be moving the battery location from the trailer tongue to a closet at the rear of the trailer, and adding portable solar panel(s).

Feedback on safety (i.e. wire sizing, fuse sizing and placement, etc.) is especially appreciated!


Notes:
  • The original converter has been removed
  • The original AC breaker panel and DC fuse panel have been retained
  • Using the Energy Audit spreadsheet I have determined maximum possible draw on the DC Panel is 48A
  • The wire run from the existing DC panel at mid-trailer back to the rear closet with LFO batteries batteries will be 10-12 FT (depending on how routing works out)
  • All wire from the battery terminals to the MRBF block terminal (+) / busbar (-) will be with 2/0 AWG wire (to allow for future upgrades)
  • Portable solar panel, SCC, and associated wire are as supplied in a solar panel kit
  • All other wire is 4 AWG
  • 2 Lion Energy UT1300 105Ah, 1344Wh, 150A LiFePo4 batteries provide the power
  • The shunt is what comes with the Victron BMV-712
  • No inverter at this time

Let me know if I can clarify anything further.

Trailer_Diagram_4-1.jpg

Thanks for your input and helping to keep my family safe!

Regards,

-Eric
 
Last edited:

McCarthy

Solar Addict
If there is any major length between the DC / solar chargers and the block I'd add a 80 / 30 amp fuse right at the charger.

With 210 A of LifePo4 batteries I'd skip on the portal solar panel (many of them are weak and take days to charge those batteries) and invest that money into at least one 460 watt panel on the roof. If you have a solar panel dealer in your area, you may get that panel for 220 bucks. You can build your own roof rack with channel struts for 150 bucks.





 

EricR

New Member
If there is any major length between the DC / solar chargers and the block I'd add a 80 / 30 amp fuse right at the charger.

Hi McCarthy,

The distance from both the AC1260 charger and the SCC to the +/- blocks will be 6-10 inches at the most. Is this OK without adding the fusing you mention?

Does the other fusing and wire sizing seem reasonable as well?
 

EricR

New Member
With 210 A of LifePo4 batteries I'd skip on the portal solar panel (many of them are weak and take days to charge those batteries) and invest that money into at least one 460 watt panel on the roof. If you have a solar panel dealer in your area, you may get that panel for 220 bucks. You can build your own roof rack with channel struts for 150 bucks.





The solar panel and SCC are already owned - purchased well before I found this site and started getting educated. :(

You are likely right! I can see myself updating the system this winter with 1 or 2 of those 460W panels you recommend - and maybe another battery or two.

Actually, late this spring I was planning a system with 400A+ LifePo4 at 24V along with 3 400+ watt solar panels (like what you recommend). I even have a Growatt 3000/24 in my garage. Not much later we upgraded our tow vehicle to a 2021 F150 Hybrid which has what Ford calls Pro Power on Board. PPoB gives 7.2Kw of 120V AC inverter power. It uses the hybrid battery to power the inverter and so the engine only runs for a couple of minutes to recharge the hybrid battery as needed. With the right adapter the truck provides 30A 120V service to the trailer, just as if we were at an RV park!

So the thought was to go out on 2-3 week long trips this fall to see how using the truck this way works out. We will bring along the existing portable panel just because we already have it, and to see how much of a hassle we find a portable panels, as some recommend putting the trailer in the shade and portable panels in the sun.

Thank you for your help and feedback!

-Eric
 

smoothJoey

SmooJo
LIABILITY RELEASE: I hereby release anyone and everyone from any and all liability related to advice given in response to this request for help. Including all replies, replies to replies, replies to my follow-up replies, etc.

Hello,

Sorry this is a cross-post. This was posted in the Safety Check section but no one has replied.

Please review and comment on this. All of my parts are in and I would really like to get started this weekend.

All help is greatly appreciated!

We have a Lance 2185 travel trailer that I am going to upgrade from FLA to LFP. At the same time I will be moving the battery location from the trailer tongue to a closet at the rear of the trailer, and adding portable solar panel(s).

Feedback on safety (i.e. wire sizing, fuse sizing and placement, etc.) is especially appreciated!


Notes:
  • The original converter has been removed
  • The original AC breaker panel and DC fuse panel have been retained
  • Using the Energy Audit spreadsheet I have determined maximum possible draw on the DC Panel is 48A
  • The wire run from the existing DC panel at mid-trailer back to the rear closet with LFO batteries batteries will be 10-12 FT (depending on how routing works out)
  • All wire from the battery terminals to the MRBF block terminal (+) / busbar (-) will be with 2/0 AWG wire (to allow for future upgrades)
  • Portable solar panel, SCC, and associated wire are as supplied in a solar panel kit
  • All other wire is 4 AWG
  • 2 Lion Energy UT1300 105Ah, 1344Wh, 150A LiFePo4 batteries provide the power
  • The shunt is what comes with the Victron BMV-712
  • No inverter at this time

Let me know if I can clarify anything further.

View attachment 65188

Thanks for your input and helping to keep my family safe!

Regards,

-Eric
Looks good.
You will be removing significant weight from the tongue and add significant weight behind the axle.
Be careful that the trailer is still balanced.

Is there a 7 pin tow cable in the mix?
What about a lead acid battery for the breakaway system?
 

EricR

New Member
Looks good.
You will be removing significant weight from the tongue and add significant weight behind the axle.
Be careful that the trailer is still balanced.

Is there a 7 pin tow cable in the mix?
What about a lead acid battery for the breakaway system?
Thanks for the feedback!

And thanks for the tow safety concern. It's one we share. The trailer has always been front heavy - I think because it has a rear "garage" storage area for bikes, etc. We will verify proper tongue weight (with a tongue weight scale) and payloads (at a Cat Scale) before we head out with the new battery setup and tow vehicle.

Yes, there is the typical 7-pin arrangement. My thinking was to simply disconnect the 12V (black) wire at the junction box mounted underneath on the frame and put a wire nut on it. So, if I'm reading the As-Built schematic from the manufacturer correctly, the tow vehicle will no longer provide charge current via the 7-pin, but the house battery will still power the breakaway system.

Here is my (crude) mark-up of the as-built schematic of the 12V system (the original is very faint so I traced over the pertinent lines):

Trailer_Pin-4_Disconnected.jpg

Since the F150's Pro Power on Board allows us to charge the batteries at any time via 120V to the AC1260 (not shown in this diagram), the house battery should always have a SOC sufficient for a power breakaway situation.

Hopefully I have this correct. Verification would be appreciated!

BTW, your comment has led to us add a step to our departure checklist to verify the battery SOC on the Victron BVM-712.

Thanks again!

-Eric
 

smoothJoey

SmooJo
Thanks for the feedback!

And thanks for the tow safety concern. It's one we share. The trailer has always been front heavy - I think because it has a rear "garage" storage area for bikes, etc. We will verify proper tongue weight (with a tongue weight scale) and payloads (at a Cat Scale) before we head out with the new battery setup and tow vehicle.

Yes, there is the typical 7-pin arrangement. My thinking was to simply disconnect the 12V (black) wire at the junction box mounted underneath on the frame and put a wire nut on it. So, if I'm reading the As-Built schematic from the manufacturer correctly, the tow vehicle will no longer provide charge current via the 7-pin, but the house battery will still power the breakaway system.

Here is my (crude) mark-up of the as-built schematic of the 12V system (the original is very faint so I traced over the pertinent lines):

View attachment 65523

Since the F150's Pro Power on Board allows us to charge the batteries at any time via 120V to the AC1260 (not shown in this diagram), the house battery should always have a SOC sufficient for a power breakaway situation.

Hopefully I have this correct. Verification would be appreciated!

BTW, your comment has led to us add a step to our departure checklist to verify the battery SOC on the Victron BVM-712.

Thanks again!

-Eric
I can't really see your drawing because I have bad eyesight.
What is c/s and r/s in terms of brakes?
Are there also breaks controlled by the blue wire in the cable?
Are you keeping the lead acid battery?
 

EricR

New Member
I can't really see your drawing because I have bad eyesight.
What is c/s and r/s in terms of brakes?
Are there also breaks controlled by the blue wire in the cable?
Are you keeping the lead acid battery?

Yes, sorry the lines are so light. No problem though. Hopefully a larger drawing and a better description will help.

C/S = Curb Side and R/S = Road Side. I just recently figured it out as RV lingo (instead of the driver's side & passenger side we use in car lingo).

Yes, the brakes are controlled by the blue wire.

No, the lead acid batteries are failing and are not included in the design. I could get a small breakaway battery, though I am thinking I don't need one.

Below I have traced over lines, added a bit of color, zoomed in and cropped out wires runs to turn-signals, brake lights, etc. If you click on the image twice it should show at full size.

The dashed line represents the junction box mounted underneath on the trailer frame. It is where the 7-pin wiring connects to the trailer wiring. I didn't bother retracing lines not pertinent to the breakaway system (turn-signals, brake lights, etc.)

The 12V+ black wire from the 7-pin is to be disconnected from the B post of the existing 40 AMP MINI BREAKER and capped off with a wire nut (represented by big asterisk (*) - as I didn't know what else to use). The new LFP batteries be connected to the existing 12V system, which includes the 12V+ black wire from the Battery Disconnect to the B post of the existing 40 AMP MINI BREAKER.

The blue wires are the 12V+ for the trailer brake system. While towing the 7-pin provides current from the in-truck brake controller.

Here is what I am planning on happening upon breakaway:
The B post of the existing 40 AMP MINI BREAKER should always be powered (unless battery disconnect is engaged). The breakaway switch completes the circuit between the B post of the existing 40 AMP MINI BREAKER and the blue wire running to the trailer brakes, energizing the brakes.​
Does this make sense? Will the trailer brakes be powered upon breakaway? Is this a reasonable way to go about this?

If not, please let me know! I really want to get all safety considerations correct! Thanks!!!

Trailer_Pin-4_Disco_Color_Crop.jpg
 
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smoothJoey

SmooJo
If not, please let me know! I really want to get all safety considerations correct! Thanks!!!
I re-did your drawing in another format as an auditing exercise.
Please check that what I did matches what you did.
Code:
dc_domain {
    pos {
        |<-disconnect<-house_batttery.pos
        |->mini_breaker->load_center.pos
        |->breakaway_switch->|->brakes.pos
                             |<-tow_vehicle_brake.pos
    }
    neg {
        |->house_batttery.neg
        |<-load_center.neg
        |<-brakes.neg
        |->tow_vehicle.neg
    }
}
if the breakaway switch is activated and the tow cable is connected and the brake pedal is de-pressed
then the house battery and tow_vehicle battery are connected in parallel

there is no over-current protection between the house battery and brakes
there is no over-current protection between the house battery and tow vehicle battery
I think that is by design because the breakaway is so critical
It bugs me though

I usually coach folks to just add a small lead acid battery and isolate the running gear system from the house system

UPDATED: make clear the brake pedal needs to be pressed for current flow between batteries.
 
Last edited:

12VoltInstalls

Solar Addict
@12VoltInstalls is interested in this stuff.
Maybe he will have thoughts to share.
If the question is the breakaway brakes you can buy a pigtailed box from a trailer dealer for about $40 or so. It includes a ?7Ah sealed lead battery. Some may last a long time but it seems to me we sold a ton of replacement batteries every year.

I hope this makes sense:
You’ll need a diode of adequate rating (if you’re using vehicle power from the 7-pin connector to charge ‘house’) to stop the house battery bank / solar from charging the breakaway battery. A fuse on the brake side of the splice makes sense too- while that 7-pin power should be fused from the vehicle PDC, it seems logical to protect the ‘second source’ from compromising the brake/vehicle wire gage in a bad but unforeseen event with a fuse as well? The seven-pin could be 8 or 10ga, while those brake battery boxes are usually 14ga or 12ga. So the fuse is at the splice.

The hard part of this is just protecting the brake box wiring while maintaining the 10ga or 8ga in the 7-pin.

The pic attached is a handy way of not having to service the terminal ends periodically- wire it up, test it, squirt it FULL of fluidfilm
The box is $10ish; you can get it premade to a trailer cord for $35-$55. Still use fluidfilm

Keep in mind if you go playing with the trailer cord that FUNCTION is how you wire it; most RVs use one color convention for the wires in the cord while utility trailer and livestock/equipment trailer cords have a convention of different colors- all the functions will be there, different colors, however. Just in case you get a different cord lol

In this way you make the brakes their own system; I prefer that method but I don’t recall seeing that oem. (99.44% of RV people aren’t going to know, understand, or want what we need)

My brakes are powered off the house batteries; I haven’t fixed it yet and I don’t really like it.
 

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shadowsteve

Solar Enthusiast
The concern in using the house battery for breakaway is if it's tripped then the tow vehicle gets reverse fed from the trailer into the brake ckt?

If the breakaway trips because of a hookup fail then the truck will no longer be connected. If it just gets pulled out by something and remains tied to the truck would a diode in series with the truck brake feed protect the truck? There would be the fwd voltage drop on the diode but that should matter.

When I switched to AGMs I just hooked them up in place of the flooded that were in the trailer. I'm doing the LFP's the same way and just tieing into the trailer 12v system where the original battery feed was.
 

EricR

New Member
OK @12VoltInstalls , I understand what you propose and it seems like clean, safe and very low maintenance solution!

Though I am curious why you "really don't like" having your brakes powered by the house battery (as that is what my current plan is)?

@shadowsteve asks some great questions as well.

Regards,

-Eric
 

smoothJoey

SmooJo
OK, I understand what you propose and it seems like clean, safe and very low maintenance solution!

Though I am curious why you "really don't like" having your brakes powered by the house battery (as that is what my current plan is)?

Regards,

-Eric
Who are you responding to?
 

EricR

New Member
I re-did your drawing in another format as an auditing exercise.
Please check that what I did matches what you did.
Code:
dc_domain {
    pos {
        |<-disconnect<-house_batttery.pos
        |->mini_breaker->load_center.pos
        |->breakaway_switch->|->brakes.pos
                             |<-tow_vehicle_brake.pos
    }
    neg {
        |->house_batttery.neg
        |<-load_center.neg
        |<-brakes.neg
        |->tow_vehicle.neg
    }
}
if the breakaway switch is activated and but the tow cable is connected
then the house battery and tow_vehicle battery are connected in parallel

there is no over-current protection between the house battery and brakes
there is no over-current protection between the house battery and tow vehicle battery
I think that is by design because the breakaway is so critical
It bugs me though
I usually coach folks to just add a small lead acid battery and isolate the running gear system from the house system

Your notation is very cool! It took looking at your notation for a few minutes until the light went on - then it was "way cool"!

Here is my attempt at an update:

dc_domain {
pos {​
|<-disconnect<-house_batttery.pos​
|->mini_breaker->load_center.pos​
|->breakaway_switch->|->brakes.pos​
|<-7pin_connector[blue]<-tow_vehicle_brake_controller.pos​
|<-mini_breaker<- *disconnected* <-7pin_connector[black]<-tow_vehicle.pos
}​
neg {​
|->house_battery.neg​
|<-load_center.neg​
|<-brakes.neg​
|​
|->tow_vehicle.neg​
}​
}

Added a line to the positive section to show the 7-pin 12V+ (black wire) from the tow vehicle is disconnected. The tow vehicle 12V system will be isolated from the trailer 12V system, excepting the brake-controller output via 7-pin (blue wire). Sometimes what's not there is as important as what is there.

Also updated the negative section to show the as-built trailer wiring has the brakes.neg and tow_vehicle.neg tied together (not sure if my notation is correct). I also updated the diagram in my original post as this was too faint to see. It was a dashed line on the original schematic so that is what I used. Though I have no idea why it is a dashed line and not a solid one.

"If the breakaway switch is activated and but the tow cable is connected then the house battery and tow_vehicle battery are connected in parallel."
Wouldn't that be: If the breakaway switch is activated and but the tow cable is connected then the brake controller is connected to the house battery?​
With our previous truck & trailer the manufacturer of the after-market brake controller warned this was condition could damage the controller and was not covered under warranty. My new shiny truck has a built in brake controller and I've not researched if this situation is a problem for this controller as well.​
Would a diode as mentioned by @12VoltInstalls prevent this problem?​

Do I need "over-current protection between the house battery and brakes"?

Since I have disconnected the wire between the house battery and tow vehicle battery, I'm thinking there can't be an over-current situation there (excepting the breakaway switch is accidently tripped situation).

A sperate breakaway system could easily and inexpensively be added, it's just unclear to me what the benefits are.

Thanks for the thoughtful input!

-Eric

Edited: Fix indentation
 
Last edited:

smoothJoey

SmooJo
Your notation is very cool!
Thanks.
Added a line to the positive section to show the 7-pin 12V+ (black wire) from the tow vehicle is disconnected.
I didn't add it because its not connected :).
Also updated the negative section to show the as-built trailer wiring has the brakes.neg and tow_vehicle.neg tied together (not sure if my notation is correct).
I believe mine already showed that.
"If the breakaway switch is activated and but the tow cable is connected then the house battery and tow_vehicle battery are connected in parallel."
Wouldn't that be: If the breakaway switch is activated and but the tow cable is connected then the brake controller is connected to the house battery?​
Means the same thing, no?
I will amend my statement to include the break peddle also needs to be de-pressed.
Which makes it less of an issue.
With our previous truck & trailer the manufacturer of the after-market brake controller warned this was condition could damage the controller and was not covered under warranty.
What condition?
Do I need "over-current protection between the house battery and brakes"?
Having your house system integrated with a system without fuses is a concern to me.
My big concern is, if anything went wrong and the break-away system failed your insurance might look for an out.
 

smoothJoey

SmooJo
Hopefully the blue(brake) wire is fused at the vehicle side.
If the 2 batteries(which may be at significantly different voltages) are connected in parallel, you will likely have fire hazard levels of current flowing through that wire.
Ironically the voltage drop of the long thin wire might mitigate things a bit.
 
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