SolarFlex 400i System

[java2d]

I am new to this forum and recently purchased a new 2023 Montana Legacy 3123RL, which came with a factory installed SolarFlex 400i solar system. Regarding RV solar systems, I am in learning mode. Can someone recommend videos available on the internet about the SolarFlex system from basic to advance information? I've watched what Keystone provides via its website, but I'm looking for more.

[Foldbak]

Welcome to the MOC! I have a 400 as well. What are you looking for? The system is very simple.

• Two 400 watt panels
• Wired directly to a Victorn solar controller/charger
• Victron solar controller wired to the batteries to provide a charge
• Victron battery shunt to allow the user to see the battery SOC
• Pre-wired for 2 additional panels. (You will need to upgrade the solar controller to accommodate more panels)

Both units have user settings to allow for lithium or LA.
Will be happy to answer more questions if you can be more specific.

[java2d]

I'm considering adding lithium batteries sufficient to allow one night's boon docking using one A/C during the warmer months of the year. The idea is to fully charge batteries on shore power before departure, travel to first stop, boon dock one night using batteries, and then travel to another location with shore power to recharge. I know an exact calculation what would require knowing the exact amperage load for the night of boon docking. I'm looking for a "guesstimate."

[Foldbak]

You'll need a substantial upgrade if you're going to run an AC. The first thing you'll need is an additional 2K inverter wired specifically for the AC. You're rig should be pre-wired in the basement.


You're going to need at least 600 amp hours to run for long periods. You'll also need a beefy solar array to charge those depleted lithium's. I'd say probably 1200 watts.

• Inverter prep
• 2K inverter
• Three 200 amp hour lithium's
• An upgraded Victron controller. To handle 600 AH
• Four more 200 watt panels

You can probably find higher wattage panels, reducing the amount but I don't know if the pre-wiring on the roof can handle higher wattage. Someone else may know

[Our3231CK]

Does anyone know how much additional weight is in a 1200W system? Adding that would require lightening the load elsewhere, wouldn't it?
I'm trying to weigh up the pros an cons as we're shopping for a new Montana with Solar this year.

[Jamric]

I have 400i solar with 2 lithium ion batteries, keeps refrigerator going 24/7! Also have 4500 watt generator

[jetskier]

Originally Posted by java2d

I'm considering adding lithium batteries sufficient to allow one night's boon docking using one A/C during the warmer months of the year. The idea is to fully charge batteries on shore power before departure, travel to first stop, boon dock one night using batteries, and then travel to another location with shore power to recharge. I know an exact calculation what would require knowing the exact amperage load for the night of boon docking. I'm looking for a "guesstimate."

a 15kBTU AC is about 14-1500W. The newer higher efficiency units may be slightly better.

Assume 13.2V battery voltage during runtime with Lithium batteries.

5 hour runtime estimate

Here's a simple calc:
1500W*5hr/13.2V=568 Ah (assumes no other 12V loads)
You'd need a minimum of 600Ah of battery storage.

I run my AC off my 3000W inverter and it will deplete the batteries to 25% in about 4 hours and that is with 600Ah and 1200W of panels on the roof. They panels only produce about 800-950W in peak sun hours. Remember panels are rated at test parameters of around 77°F and lose efficiency as the surface temp of the panel increase.

Other loads I have at the same time are the 12V cooling unit on my Norcold 2118 and all the other draws (lights, phone chargers, etc.)

[Foldbak]

Originally Posted by Our3820FK

Does anyone know how much additional weight is in a 1200W system? Adding that would require lightening the load elsewhere, wouldn't it?
I'm trying to weigh up the pros an cons as we're shopping for a new Montana with Solar this year.

The weight is negligible. The panels weigh about 12 lbs. The control equipment and inverter is also light. Two 100AH lithium's weigh 50lbs verses 150lbs for lead acid. So it's a no brainer.

[RacerX]

Originally Posted by Foldbak

You can probably find higher wattage panels, reducing the amount but I don't know if the pre-wiring on the roof can handle higher wattage. Someone else may know

What I have seen on the Keystone Cougar side is a second loop of wires to the roof and the battery as a “solar prep” for a second charge controller vs a larger one. Re the wiring, it appears to be 10awg. Rather than pulling bigger wire I would lean toward hooking up additional panels in series to the new 2nd charge controller….thereby doubling the voltage but keeping the amp current lower . All depends on the panels selected and whether doubling their open circuit voltage would fit under the 100v max of the 100/30 SmartSolar MPPT.

[jetskier]

Originally Posted by RacerX

All depends on the panels selected and whether doubling their open circuit voltage would fit under the 100v max of the 100/30 SmartSolar MPPT.

....and the 30A limit to the batteries

[Jay Merritt]

On our 2016 3611 RL Legacy, I installed 2000 watts of residential panels on the roof, 1200ah of LiFePO4 Lithium batteries, two Victron solar chargers, two Victron 3000 Inverters, and a Victron BMV-712.

We have a residential fridge we need to maintain. We set our expectations to 4 days between full hookups, in case if clouds and/or tree cover. We have two small generators just in case, but have not needed them this year.

Lithium batteries make a huge difference compared to AGM we had on our previous rig.

[sidgod1018]

I have a 2020 Montana 3791 Rd. I bought used. I think I found the wire in the basement bit I cant find where on the roof I can get access to it. Please help

[Foldbak]

Originally Posted by sidgod1018

I have a 2020 Montana 3791 Rd. I bought used. I think I found the wire in the basement bit I cant find where on the roof I can get access to it. Please help

You should have something like this on the roof. If not it's likely your rig wasn't solar prepped.

[sidgod1018]

Thank you for your response. I do not have that on my roof.

[sidgod1018]

Thank you for your response. I do not have that on my roof. If i had to cut into my roof to install, where would you recommend me drilling a hole so i can wire future panels? Thanks again

[Foldbak]

Be careful where you drill. Especially on the roof. SO much wire, plumbing and ducting up there. If it were me I'd find a closet and open the ceiling to find a clear spot. A lot of peps here have installed extensive solar systems. I defer to them .

[jetskier]

Since you have a 3791, you can run them down the wall behind the buffet. There are two vent pipes for the bathroom and waste tanks. If you remove the control panel in the upper cabinet with all the switches, you'll see the wall is opened up and the two pipes are there. They run from the basement to the roof along with a ton of the wiring. When you get on the room, you'll see them. This weekend, I used this area to add two more sets of wire to expand my system and used this chase to run them down. I used a 1.5" hole saw and carefully drilled through the 3/8" roof plywood about 4-5 inches laterally away from the two plumbing vents since they line up with the wall below. Make sure to pull the trigger on the drill so you can stop it from spinning as it breaks through. When I pulled the drill, there were a few of the 12g Romex runs (probably for the ACs). I used my fish tape to probe along side and it dropped in the wall cavity right to the open space behind the switches. I pulled the wire to there and then ran the fish tape down to the basement and pull the other end down there.

[sidgod1018]

That sounds like wonderful advice. Im o happy for the information. Thank you. Thank you. This is a great thread with alot of helpful people.

[sidgod1018]

Do you have any photos of the job you did? just looking for reference. Thank you again. It was very helpful

[jetskier]

Here you go.... I'm still in the process of adding the 4 additional panels from my original six in the photos, but the two new solar circuits are there next to the vent pipes. The factory solar connection location is hidden by the kitchen AC, but it looks like the photo posted above by Foldbak. The new work hasn't been sealed yet, but I'm still waiting for the panels to arrive before I get the lap sealant out for all the penetrations.

The photo of the basement area is where the two sets of wires comes through (black and red above flex duct/over sewer pipe). You can see the chase way in the background. That's the area behind the buffet cabinet.


The factory location of the solar charger is behind the convenience center. It's not as big as the one I have there (Victron 150/85). I added two more 100/50 in the battery compartment along with the mess of other fun toys in there.