Upgrading RV Solar - System Check Please

[NorCalPete]

I'm seeking advice/corrections/comments about my RV's (i.e., 21' travel trailer) solar upgrade project - my system diagram is attached. I'm swapping in two SOK-206ah batteries (prior was a pair of Trojan T-105s) and two 200 watt roof panels (prior was a single 130 watt panel), upgrading the old converter module to lithium (PD-4045LICS), and adding a Giandel PS-2200KAR inverter and TS-30 automatic transfer switch. Along with these items, I'm adding/upgrading switches, fuses, breakers, buss bars, and wiring as needed. One SOK-206 (purchased in February) came without Bluetooth, while the second one (received in May) came with Bluetooth; by my request, SOK shipped me an "old model" BMS (without bluetooth) so I can convert the newest 206 battery to match the first one. We also have two portable 130 watt flexible solar panels (mounted on PVC frames) we use to supplement the rooftop panels when parked in the shade.

We are primarily three-seasons boon-dockers, usually camping 4-10 days in shaded State Park sites during cool-to-hot weather (40-90 degrees). Currently, we use a 2500w inverter generator to charge batteries (daily in cold weather; every 3 days when moderate), run the microwave, and run the A/C in hot weather (although very rarely). My goal is to eliminate the need for the generator except to run A/C.

At home the trailer is parked in our driveway, connected to shore power (30 amps), and used occasionally as a home office. The goal is to run it on solar at home except when A/C is needed, and to utilize excess solar capacity to power one or two 120 volt circuits in my house. A 10-gauge extension cord will run from the trailer (i.e., from the refrigerator's 120 volt ac outlet) to the house's manual transfer switch (installed for my generator).

So those are my goals, along with my current plans for implementing them. Your comments or suggestions would be greatly appreciated.

 

[HRTKD]

I would not combine the the two solar strings. Use separate controllers. The panels are different enough that you'll not get optimal output by combining them. I would run them in series (2s) if the solar charge controller can handle the PV voltage.

If you went with an inverter/charger instead of separate inverter and separate charger you could avoid the ATS, converter and the switch.

The battery switch is usually on the positive leg, not the negative.

 

[corn18]

Solar panels:

Wiring the roof panels in parallel is not optimum. The reason is they are only 20.4V Voc. Your MPPT controller will need 19.6V to spit out 14.6V for the absorption charge to your SOK batteries. So, put them in series. I also recommend a separate controller for the ground mount panels. And keep them in series.

Ditch the 25A T-Tocas breaker on the MPPT output and get a good Bussmann or Blue Sea Systems breaker.

DC:

The 60A fuse for your DC loads should be on the other side of the 250A type T fuse for your inverter. The reason is that if the inverter fuse blows, you now have no power to the DC side either.

The 30A fuse in line with the electric jack fuse is redundant. I know manufacturer's wire it that way. A fuse on the wire feeding the e-brake switch is not ideal but I know why the manufacturer's do that. I would remove the 30A fuse and keep the 30A resetable fuse on the jack. You don't want a blown fuse when you need e-brakes.

AC:

I second the recommendation for an inverter/charger. Will make your install and operation a whole lot simpler.

 

[NorCalPete]

HRTKD and corn18, thank you for your feedback and suggestions. Given that I often camp in shady spots, I thought that wiring the rooftop panels in parallel would be optimal due to shading issues; is that not the case?. When parked at home, however, the trailer does have unobstructed sunlight so wiring them in series would be optimal for that location. Regarding the placement of the 250A fuse, I thought that was supposed to be my "fail safe" fuse to disconnect everything -- I didn't realize it was intended only to protect the inverter.

I already have some of the components in hand, so I won't be going the inverter/charger route, but I will implement your other suggestions. BTW, I never understood why the manufacturer installed that 30A fuse in front of the e-brakes; in a braking situations, I'd rather risks my wire versus losing my e-brakes.

 

[corn18]

HRTKD and corn18, thank you for your feedback and suggestions. Given that I often camp in shady spots, I thought that wiring the rooftop panels in parallel would be optimal due to shading issues; is that not the case?. When parked at home, however, the trailer does have unobstructed sunlight so wiring them in series would be optimal for that location. Regarding the placement of the 250A fuse, I thought that was supposed to be my "fail safe" fuse to disconnect everything -- I didn't realize it was intended only to protect the inverter.

I already have some of the components in hand, so I won't be going the inverter/charger route, but I will implement your other suggestions. BTW, I never understood why the manufacturer installed that 30A fuse in front of the e-brakes; in a braking situations, I'd rather risks my wire versus losing my e-brakes.

Parallel is better in shady situations, but you won't have enough voltage to feed the MPPT controller. The 20.8V Voc of your roof panels is barely enough. So in this case, I would make the trade-off for better overall performance.

 

[HRTKD]

BTW, I never understood why the manufacturer installed that 30A fuse in front of the e-brakes; in a braking situations, I'd rather risks my wire versus losing my e-brakes.

The emergency trailer brake system shouldn't pull more than about 12 amps. But if it does, something is wrong and the fuse will come in handy. Over on the Ford Truck forum a guy posted that his trailer almost burned down because the breakaway pin was accidentally pulled. A while later, the wire was a smoking, melted mess.

 

[HRTKD]

My experience is that you're either in shade, or you're not. I can pick where I park my RV since I'm boondocking most of the time. If I'm forced to be in a campground (

) I try to preview the sites, looking for one with the least amount of shade.

Camping in the west is different than the east/south with all those pesky trees that get in the way.

 

[corn18]

The emergency trailer brake system shouldn't pull more than about 12 amps. But if it does, something is wrong and the fuse will come in handy. Over on the Ford Truck forum a guy posted that his trailer almost burned down because the breakaway pin was accidentally pulled. A while later, the wire was a smoking, melted mess.

I went through this dilemma with my install. I didn't like a 10ga wire going to the e-brake disconnect switch with no fuse. I also didn't like having a fuse feeding the e-brake disconnect. I solved the problem by installing a dedicated battery right at the e-brake disconnect switch. It charges from the original 10ga feed wire with a 30A fuse. So all wire is protected and the e-brake switch is not fused.

 

[NorCalPete]

Camping in the west is different than the east/south with all those pesky trees that get in the way.

Pre-solar, finding/creating shady spots always was my goal, both for camping and my house. Now, all those trees are inhibiting solar production on both my trailer and house (which has a neighbor's massive redwood trees blocking my entire western roof exposure). Still, I harvest whatever solar I can.

 

[NorCalPete]

I went through this dilemma with my install. I didn't like a 10ga wire going to the e-brake disconnect switch with no fuse. I also didn't like having a fuse feeding the e-brake disconnect. I solved the problem by installing a dedicated battery right at the e-brake disconnect switch. It charges from the original 10ga feed wire with a 30A fuse. So all wire is protected and the e-brake switch is not fused.

Does that mean the dedicated e-brake battery is connected to the same system as your other coach batteries? Wouldn't that create additional issues with your coach batteries (i.e., mismatched capacity [if the e-brake one is smaller], or different wire resistances if it is located farther away)?

 

[corn18]

Does that mean the dedicated e-brake battery is connected to the same system as your other coach batteries? Wouldn't that create additional issues with your coach batteries (i.e., mismatched capacity [if the e-brake one is smaller], or different wire resistances if it is located farther away)?

It is and it isn't. It is a dedicated battery kit that is made for e-brakes.

https://www.amazon.com/gp/product/B07YD5Q2MV/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[HRTKD]

Does that mean the dedicated e-brake battery is connected to the same system as your other coach batteries? Wouldn't that create additional issues with your coach batteries (i.e., mismatched capacity [if the e-brake one is smaller], or different wire resistances if it is located farther away)?

In my case, I did a similar setup. An isolated, smaller lead acid battery on the tongue that is charge by the 7-pin circuit and a dedicated solar panel and controller. The "house" LiFePO4 battery bank has nothing to do with the battery on the tongue. The 7-pin charge goes to only the tongue battery. It was a concession. I had a spare lead acid battery, needed to get it done and wasn't too keen on using my LiFePO4 battery bank to start the 5500 watt on-board generator. The bonus is that I could completely drain my house batteries and still start the generator.