What's missing with this T@B 320S solar port install?

riseandshine

Before the start of the Spring camping season we're going to install a solar port for connecting a suitcase-style portable solar panel to our T@B 320 S. While the OEM solar panel on the roof does a pretty good job keeping the batteries charged most of the time, more solar charging would help during partly cloudy weather and when camping with tree cover. It would also be good to upgrade some of the wiring done by the dealer in the tongue box during this project.

Dealership Wiring Issues:

• The dealer installed the two 6V batteries and a Victron 712 smart shunt. Everything works and we have not blown any fuses, but... 
• The dealer did not include bus bars near the battery, so two sets of cables connect directly to the battery terminals, and I'd like to avoid adding more wires to the battery terminal during this upgrade. 
• There is no terminal fuse with a high AIC amperage rating on the battery's Pos+ terminal. I thought a high AIC terminal fuse was standard procedure for systems like this. Presently there are two 20A ATC/ATO blade fuses (auto fuses) with inline fuse holders on the Pos+ wires (looks like 12 or 14 AWG) connected directly to the battery terminal, one going to the OEM solar controller, the other going to the 7 Pin DC junction box. 
• The two auto fuses above will be replaced with MIDI fuses inside covered fuse holders. My understanding is that MIDI fuses coming off a Pos+ and Neg- bus bar connected down stream from the battery/smart shunt is a safer option than cheap inline blade fuses. 
• The OEM solar charge controller's wires bypass the battery shutoff switch - not sure if there's a reason the shutoff switch should not shut off everything, including solar.

After reading through many posts on this forum and watching lots of DIY solar videos, the wiring diagram and parts list below is what I've come up with, based on our current setup and usage as detailed below. I'd love to hear your feedback on the install, the parts and the wiring diagram, especially anything that's missing or inappropriate.

Current Setup and Usage:

• Trailer: 2020 Tab 320S Boondock with OEM solar, OEM WFCO 8735-P AC-DC converter, OEM MPPT 75/10 solar controller.
• Battery specs: Interstate GC2-ECL-UTL, 6V 225Ah each, 2 in series = 12V 225Ah total, 110Ah usable. Total watt hours: 1350Wh. Max charge rate = Ah x 15% = 225 x 0.13 = 29 amps per www.interstatebatteries.com/support/golf-cart-battery-installation-and-maintenance.
• Electrical Additions: Victron 712 battery monitor/shunt.
• Typical usage: 5 - 10 day boondocking trips in Western U.S., often staying in one place for 3 - 5 nights without tow vehicle charging. We rarely use shore power.
• Sun exposure: typically good partial sun each day, except for overcast weather periods, where current batteries get close to 50%.
• Typical electrical usage: Continual 12V refrigerator use on all trips. Laptop & camera charging. No AC, no microwave, no inverter.
• Portable solar generator: BLUETTI EB55 700W/537Wh Portable Solar Generator with 120W Solar Panel, for occasional 110V appliance usage.
• Existing T@B 320 OEM roof solar panel: Power: 133 W, Voltage: 12 V, Current: 11 Amps max, 10 Amps/Hr.
• Portable suitcase solar panel: Bluetti PV120: 120 W (240 W for two), Voltage at Max Power(Vmp): 19.6 V (40V if two panels in series), Current at Max Power(Imp): 6.1 A (12.2 A if two panels in parallel), Open Circuit Voltage(OCV): 24.4 V, Short Circuit Current(Isc): 6.43 A, Cable: 10 foot long, 16 AWG cable, two (+red and -black) male-to-female MC4 connectors in the middle of cable. Cable end is XT60 female connector.

Wiring Diagram:


Installation and Parts:

• Install a male XT60 mount panel (solar port connector with weather resistant cap, with integrated 12 AWG cable) onto the outside of the tongue box, for the portable solar panel. Comes with 3 feet of 12 AWG cable attached: https://amzn.to/49TwBiv 
• Install a dual-pole solar disconnect switch/breaker (16 amp breaker) with distribution protection box, mounted inside tongue box: https://amzn.to/3SPziuq  https://amzn.to/3OYEcEo  
• Install a second charge controller (Victron MPPT 100/20) dedicated for portable solar panel. Mount to plywood sheet inside tongue box:  https://amzn.to/48zHzsm  
• Install pair of 250A 6 x 5/15" stud bus bars (+red and -black):  https://amzn.to/49MVRXP  
• Install three MIDI fuse holders to plywood sheet inside tongue box. Two 20A fuses (both solar controllers) and one 30A fuse (WFCO/DC Junction Box cables) :  https://amzn.to/4a71tMr  
• Install 40A MRBF terminal fuse with 10,000 AIC directly to battery Pos+ terminal:  https://amzn.to/4cg2nrE  
• Pure copper wire, black and red, 6 AWG and 12 AWG (properly crimped with terminal lugs or wire ferrules):  https://amzn.to/4caGDxz  https://amzn.to/4a8fw4d

pthomas745

In my 320, with the SAE port, the battery wiring with the solar wiring is as you describe: a positive and negative on each terminal, one set of wires going to the battery switch for the trailer, and the other set to the solar port on the side of the trailer.  In my 2017, only the cables going to the battery switch have a 30 amp ATO fuse.  My 2017 does not have a fuse on the solar port cables, but I understand the newer builds with the ports are fused.  I'll leave the idea of different fuses to someone else, since it is far above my pay grade.

The battery switch is designed with the switch to disconnect the battery to eliminate parasitic drain from the trailer while the trailer is "stored" or between trips with no shore power attached or needed.  The solar is hard wired to the battery so that if you do not have shore power, but want to keep the battery charged between trips, you can do so with the battery switch off, preventing parasitic drain. 

riseandshine

Good point on letting the roof solar system charge the batteries even if the disconnect switch is isolating the battery. The wiring diagram has been updated accordingly below. As for fuse sizes (and wire sizes), that's what I'm most interested to hear feedback on, most especially the battery Pos+ terminal fuse amperage rating.

Maxcamp

Like your diagram.  I'm planning something similar as part of an electrical upgrade, including a 200w solar suitcase auxiliary.  Ordered a 30ft 10awg umbilical and SAE connectors, but like your XT60 connectors better.  Had not seen a DC two-pole breaker and like the idea rather than separate inline switchable breakers on pos and neg. 
Thanks for posting.

SLJ

I'd seriously ditch those heavy slow charging lead acid batteries you can only use half of first and switch to lithium before anything else. New solar controller with charge two 100AH lithiums to 100%. Then go from there. You can get a reliable 100AH battery with low temp cut off now for under $300.
When you add portable solar, Make sure to move the controller into the tub. You will get a lot more charging power from the portable panels if the long cable voltage drop is before the controller, not between the controller and the battery.

Marceline

I added a solar controller and an SAE port for a portable 160w panel in the front tub of my T@B, and I approximately followed this schematic from Sun Powered Yachts. I have SmartShunt instead of a BMV712 and I don't have the battery sense. 

The break in the line between the controller and the panel is where I have the SAE port. Per the schematic below, I have this marine circuit breaker between the controller and the battery. Your bus bars are probably a good idea.

riseandshine

Glad the diagram was helpful Maxcamp8 - I look forward to seeing your upgrade on the forum. The DC two-pole breaker idea came from this video: https://youtu.be/HOXnWXvLXko?si=7YO4prBC7RXfkCaK

I hear you SLJ, I'd love to upgrade to Lithium, move all the electrical inside the trailer and have lots of storage opened up in the tongue box. My wife is nearly on board with a either a 206Ah or 280Ah SOK LiFePo4 battery plus inverter install, but we may put that off till later in the year and just do the solar port now. 

Thanks Marceline - I like your idea of using a circuit breaker instead of an expensive fuse as the main battery Pos+ terminal protector, especially as we're considering upgrading to lithium battery, which can handle much higher charging and discharge current. How did you choose the 25A rating for the breaker?

Marceline

riseandshine said:

Thanks Marceline - I like your idea of using a circuit breaker instead of an expensive fuse as the main battery Pos+ terminal protector, especially as we're considering upgrading to lithium battery, which can handle much higher charging and discharge current. How did you choose the 25A rating for the breaker?

The breaker was recommended by a technician at Bay Marine Supply. I was originally connected with Bay Marine Supply by Victron and I've been getting advice and buying equipment from them since 2020. Both Bay Marine & Sun Powered Yachts recommended the 25A circuit breaker. I have a vague memory that I was originally going to get a similar 30a breaker but it was unavailable because of supply chain issues. I installed everything two years ago.

riseandshine

FYI, this install just got upgraded to also include a LiFePO4 battery swap-out, inverter and charger install, and an inside-trailer battery relocation. I'll make a separate post for the new install. Thanks again everyone.