Advice appreciated - wiring diagram for truck camper upgrades

[kjkeiter]

Hi all:
I just bought a used truck camper and am planning to modify it for more effective boondocking. I think I have a pretty good wiring diagram pulled together but would sure appreciate any input and advice you all have. The existing system has dual LA deep cycle batteries, a WFCO 8955PEC power center and a 2019 40amp solar controller fed from a 200W panel on the camper.
I've purchased a group 31 LiTime 140aH battery, a Victron Orion 12/12 30amp DC DC charger, a Victron Smart Solar 100/20 isolated charge controller, a couple of bus bars, two 40amp breakers, a bunch of 6Ga wire and a few more odds and ends. I'll be placing the battery under the seat in the dinette instead of the current location near the back corner of the camper (outside access) so I can keep the battery warmer and have the battery closer to the loads. I do not intend to install an inverter at this time since we don't really need 120v AC while boondocking. (I do have a Bluetti EB70 for rare situations that require it.)
I'm wondering if I have a good handle on the wiring setup. I don't think we'll ever flow more than 40 amps to the loads but the WFCO can send up to 55amps to the batteries if we happen to be on shore power. By the way, on the diagram, the line disappearing off the paper on the left side of the page is shore power (up to 30amps).
My concerns are:
1. Should the battery disconnect (new) be on the positive or negative side? I have read negative is better but that didn't seem logical to my ME brain. If I was an EE maybe it would.
2. Do I have enough fuse and breaker protection installed?
3. Should I be removing the power from the 7 pin connector? My understanding is that the little bit of power to the batteries from the 7 pin is so small that it won't matter compared to 30amps from the Orion and up to 20amps from the solar panels. Just wanting to make sure that I don't overlook something.
3. Is there anything else I'm overlooking?
Thanks very much for any advice you can offer!

 

[OTRwSolar]

A few initial observations. No doubt others will chime in with a few more.

WFCO converters are notorious for rarely going into or staying in bulk (14.4 - 14.6v) mode. They tend to stay in 13.6v absorption mode, significantly increasing charge times (due to reduced charge current). I'd discharge the lifepo4 a good bit, temporarily connect the WFCO to the lifepo4, and confirm whether it goes into and stays in bulk mode (producing its rated 55a of charge current)---before committing to the WFCO.

Suggest placing the fuse for the dc2dc charger input as close as possible to the vehicle battery terminal. Placing the fuse on the TC side of the TC/vehicle connector (as shown in your wiring diagram) can potentially leave all the cable/wire between the TC/vehicle connector and the vehicle battery unprotected.

If your vehicle does not disconnect the primary pos power to the 7-pin connector when the vehicle's ignition is turned off, then it's best to disconnect the TC from the 7-pin connector when the vehicle engine is not running for longer periods of time. This prevents the TC from potentially discharging the vehicle battery (especially while dry camping/boondocking overnight).

 

[chrisski]

Disconnect should be on the positive side. This negates the possibility of current flowing through a ground.

For removing power off the 7 pin, it’d be better not to, but if so maybe less than 20 amps will work.

This will provide DC power but if you run the heater all night long, you may a single 100ah battery may not be enough. The propane fan motor draws about 100 watts.

 

[kjkeiter]

This is really helpful input!
@chrisski, I'll leave the 7 pin connected, as you suggested. I didn't mention that the camper has the Alde heater system (hydronic) with just a pump so the power draw is less than traditional but it seems like your suggestion is still wise.
@OTRwSoar, my WFCO isn't designed for lithium but I can buy a module that is for about $80. I've read mixed reviews about the benefit of doing it, especially as we won't be on shore power very often. My main initial concern was that the two Victron units (DCDC and Solar) would get confused by the WFCO. I'll also move the breaker/disconnect for the DC DC to the engine bay near the battery connection.
Appreciate the input and look forward to any other helpful advice!

 

[MattMan119]

I would place two fuses or breakers in these areas to prevent the big circuits from having bad things happen:

1) Something for a max from batter, maybe your batter had protection and maybe not. From the results i have seem i would not trust them and would put something here to save that 6gauge wire from meltdown.
2) Main feed from bus .. this is another 6gauge that i would protect.

I would place them both as close the source as possible, at battery going to bus, at bus going to panel.

 

[OTRwSolar]

@OTRwSoar, my WFCO isn't designed for lithium but I can buy a module that is for about $80 . . . .

The gist of my comment about the WFCO boils down to whether you may have to wait 6-7 hours to charge your lifepo4 at 13.6v vs. ~3 hours at 14.4 - 14.6v volts (bulk mode). This is not a lithium compatibility issue, but an operational deficiency that tends to affect many WFCO converters----their tendency to rarely transition to bulk mode.

Ref leaving or not leaving the truck camper's 7-pin connected to your vehicle, do you know whether your vehicle turns off the primary pos power to the 7-pin connector when the ignition is turned off? If the vehicle does *not* turn off power to the 7-pin connector (and it's left connected to your truck camper), your truck camper could potentially discharge your vehicle battery (while dry camping/boondocking), leaving you with no way to start your vehicle.

I might add a dc2dc charger could potentially discharge your vehicle battery in the same manner . . . unless you install a battery isolator (or something equivalent). A BI disconnects the dc2dc charger from the vehicle battery when the alternator is not active (i.e., vehicle engine is not running).

 

[chrisski]

For the Ac to Dc converter, how often will you use it?

I don’t use mine except for once a year to test. For me, a 13.6 VDC converter with all charging coming from the solar would be fine.

 

[kjkeiter]

Thanks again for the input, everyone!
@MattMan119, that's good input on protecting those additional two wires. I'll incorporate that.
@OTRwSolar, great input! I am 99% sure the 7-pin is only live when the key is in the 'on' position in the truck but I will verify. I'm not too worried about 6-7 hour charge time for those rare occasions when I'm using the WFCO to charge the batteries. That would be at home or in a campground where I will keep it plugged in overnight. I can spend $80 to update the charger module but will wait and see, I think. Finally, I'm almost sure that the Victron Orion does isolate the DC DC charger from the truck battery when the truck is off. I'll confirm that. It has a sensor that detects when the engine is running before it begins to charge.
Still welcoming feedback! The work is a couple of weeks away but I hope to complete it before a post-Christmas road trip.
Thanks!