New 24v/3000w Growatt system design for Keystone travel trailer. Thoughts?

[Deek Johnson]

Hi all...finally getting around to finishing this project and working out the kinks. This is being installed in a 35' Keystone 395RE trailer with a rear living floor plan.

1. The plan is to remove the hidden TV in the entertainment cabinet at the back of the RV and replace with the Growatt controller (will raise up and down to hide like TV does). Lots more wasted space in there so got 2 BigBattery Hawk batteries to fit. My son is helping who lives/works on the road full time in trailer and has put in a few systems for himself. We're thinking I'll probably need some switches/fuses but this is what we have so far. Would appreciate your comments.

2. The overall plan is to redirect the shore power cable to run directly into the growatt, and then the growatt output would reconnect back into the OEM circuit box on the floor that then feeds the fuse panel. The Growatt would manage all incoming/outgoing energy (shore power and solar/to charge batteries/energy draw from battery or shore, etc).

3. Also trying to set it up so I can easily bypass the Growatt/solar system (if something should go wrong that I can't fix right away) by simply unplugging the incoming shore power back into the OEM circuit box.

4. A few questions remain regarding not having equal length wires between panels, as I had to mount 2 panels further forward on roof...does it matter?

5. Does running ground panels and roof panels w different voltages together into parallel circuit cause an issue...will only be using ground panels if I have to (sitting in shade or extra cloudy)?

Anything else you folks can see please feel free to comment. Good news so far is I don't think I have any suicide cables!!!

Thx for your help
Deek

 

[Deek Johnson]

In case you have trouble viewing the PDF...

 

[John Frum]

The ac2dc converter in the ac/dc distribution panel are typically very inefficient.
Just sayin.

 

[LSC]

I am still learning but the solar Voc voltages at the MC-4 connectors doesn't look right. ??

 

[McRod]

Hi all...finally getting around to finishing this project and working out the kinks. This is being installed in a 35' Keystone 395RE trailer with a rear living floor plan.

1. The plan is to remove the hidden TV in the entertainment cabinet at the back of the RV and replace with the Growatt controller (will raise up and down to hide like TV does). Lots more wasted space in there so got 2 BigBattery Hawk batteries to fit. My son is helping who lives/works on the road full time in trailer and has put in a few systems for himself. We're thinking I'll probably need some switches/fuses but this is what we have so far. Would appreciate your comments.

2. The overall plan is to redirect the shore power cable to run directly into the growatt, and then the growatt output would reconnect back into the OEM circuit box on the floor that then feeds the fuse panel. The Growatt would manage all incoming/outgoing energy (shore power and solar/to charge batteries/energy draw from battery or shore, etc).

3. Also trying to set it up so I can easily bypass the Growatt/solar system (if something should go wrong that I can't fix right away) by simply unplugging the incoming shore power back into the OEM circuit box.

4. A few questions remain regarding not having equal length wires between panels, as I had to mount 2 panels further forward on roof...does it matter?

5. Does running ground panels and roof panels w different voltages together into parallel circuit cause an issue...will only be using ground panels if I have to (sitting in shade or extra cloudy)?

Anything else you folks can see please feel free to comment. Good news so far is I don't think I have any suicide cables!!!

Thx for your help
Deek

The different length of solar panel wires does not matter.

The different panel voltages does matter. It will reduce the efficiency of the system. The math I use to determine the change is:

Formulas for mixed panels:
1. Series: (Volts + Volts) * lowest Amps = Watts

2. Parallel: lowest Volts * (Amps + Amps) = Watts

To prevent this you can purchase a second charge controller and run your portable on its own line to the batteries. You can buy the zamp solar port on Amazon and plug your ground mount into it. The combination of charge controllers shouldn't exceed your max charging rate of your batteries.

 

[Deek Johnson]

The different length of solar panel wires does not matter.

The different panel voltages does matter. It will reduce the efficiency of the system. The math I use to determine the change is:

Formulas for mixed panels:
1. Series: (Volts + Volts) * lowest Amps = Watts

2. Parallel: lowest Volts * (Amps + Amps) = Watts

To prevent this you can purchase a second charge controller and run your portable on its own line to the batteries. You can buy the zamp solar port on Amazon and plug your ground mount into it. The combination of charge controllers shouldn't exceed your max charging rate of your batteries.

Thanks...yea, so ordering a separate controller for the roof panels w bluetooth/app monitoring and will use the Growatt solar for ground panel input, with battery cables from both controllers running to a bus bar, then bus bar into the growatt. I'll re-illustrate and post. Thx

 

[Deek Johnson]

Updated layout...added 2nd controller and laid the batteries down, that just fit. More stable and can read front LED panel way better. Also included a pic of the rear entertainment area w lots of space behind. Will also be replacing the bottom 2 shelves in the front with electric fireplace/heater insert. Fingers crossed all goes well. Trying to get all done before Zombie apocalypse by end of summer LOL

 

[McRod]

Updated layout...added 2nd controller and laid the batteries down, that just fit. More stable and can read front LED panel way better. Also included a pic of the rear entertainment area w lots of space behind. Will also be replacing the bottom 2 shelves in the front with electric fireplace/heater insert. Fingers crossed all goes well. Trying to get all done before Zombie apocalypse by end of summer LOL

Wait.. are the two panels on the ground identical to the panels on the roof? You just don't have enough roof space?

If so, you should try to wire them 4s2p. That will require some wiring extensions.

If not, then wire them as below:

The second charge controller doesn't wire into the growatt. I would wire your main roof panels directly into the growatt PV input.

Wire your smaller ground panels directly to the smaller second charge controller and then directly to the batteries. They need to be independent to avoid the panel inefficiency. The only draw back to this is your creating two independent systems, so you will monitor them separately.

Let me also add: looking at your roof layout and measurements, you may have room for the two ground panels on the roof. 1 center/front. 1 center/back. If you can get them up there that would make all of this mute. Wire them 4s2p.

 

[Deek Johnson]

Yes, all panels are the same, and yes I have room on the roof for 2 more (down the center). That was the original plan, but if in the shade, wanted option to move a pair of ground panels out to sunlight, and also to be able to follow the sun through the day. The ground pair of panels would be hinged and carried on back bumper on their side between trailer and spare tire. Would make a simple holder/rack that I can lock them in with cover.

Yes, makes sense to hook up roof panels to growatt (also have wifi dongle) but the Victron has Bluetooth w phone app capability, and since roof panels are always being used, was thinking this monitoring capability would be valuable...???

Doing more research on how to integrate the second controller and ground panels into the battery management system.

Thx for your help

 

[McRod]

Yes, all panels are the same, and yes I have room on the roof for 2 more (down the center). That was the original plan, but if in the shade, wanted option to move a pair of ground panels out to sunlight, and also to be able to follow the sun through the day. The ground pair of panels would be hinged and carried on back bumper on their side between trailer and spare tire. Would make a simple holder/rack that I can lock them in with cover.

Yes, makes sense to hook up roof panels to growatt (also have wifi dongle) but the Victron has Bluetooth w phone app capability, and since roof panels are always being used, was thinking this monitoring capability would be valuable...???

Doing more research on how to integrate the second controller and ground panels into the battery management system.

Thx for your help

Ok. Since they are the same panels and you want the flexibility, I would just put them on their own controller like mentioned above.

That's very simple to do. You wire the two panels in series (+ to -) and then run the left over + and - to the scc pv input. Then you run the + and - directly to the battery + and -. I would put a standard blue sea cutoff switch between the PVs and the SCC. Should not need one between those batteries and the SCC because they have built in on/off switch and fuses. You can monitor the Victron SCC via bluetooth on your phone or use V.E direct to connect to wifi.

 

[Deek Johnson]

OK...soooooo...here's an update. Original plan was all 8 panels on the roof...but decided to keep two as ground panels in case we're in shade. But if I had these 2 panels outside the series I'd need a 2nd controller/charger (trying to avoid). Soooo...was thinking of doing this. Is this crazy stupid or would this work?

I am trying to add the extra ground panels from each series into the existing series (see A). When panels are not being used I would use a jumper cable (see B) to complete the series circuit. Yes, more wire more loss, but would additional 420w offset the loss of energy in the extra wire?

Would require two separate runs on wire from roof, and also 2 runs of wire out to solar panels, but no need for separate controller/charger. I'm using the romex-style marine-grade solar cable w both +/- cables in a single sheath). I would wrap these two cables into one for easy transport and use.

I am trying to reach solar capacity on ideal conditions to run the RV AC w minimal battery drain.

Thx for all comments!

 

[McRod]

Yes, that's the right way to wire it.

However, based on your last comment, you may end up disappointed in your systems ability to run the factory A/C. As a solar system, its just not enough, unless you are trying to intermittently run the A/C in 80° weather. Can the A/C turn on? Yes, but don't expect to run the A/C and charge your batteries in any weather that actually requires A/C, like 95°+

Remember, when the sun goes down, you may still need your A/C, so you will be relying on your batteries only. The next morning your solar system must be able to quickly charge up your batteries and also run the A/C.

Let me explain it in simple mathematical terms.

Assume your A/C unit uses 1200 watts at 120v. That's 10 amps per hour (1200/120=10). That's being generous. Your factory A/C probably uses a constant 1500w, not including startup surge.

You have 2 ea 175 AH batteries at 24v. That's 350AH at 24v.

For basic simplicity, your inverter must inverter the 24v to 120v. That's equal to 5x (120/24= 5). This does not include inverter efficiency, ohm loss, or other factors for a perfect calculation. This is basic math.

Since your AC uses 10AH at 120v, it will use 50AH at 24v from your batteries. (10AH x 5= 50AH).

With only 350AH available, you will completely discharge your batteries in 7 hours (350ah/50ah=7) with no battery charging, either DC charge from your panels or AC charge from shore.

Your solar system is 1680w at 24v. That means the maximum AH recharge of your batteries is 70AH. (1680w/24v=70A). Again, that's in a "perfect world" where 100% of your panels are facing exactly perpendicular to the sun, from sunrise to sunset. That's not going to happen.

So in a perfect world you would have 70ah, running your 50ah A/C.

In the scenario above, we didn't discuss any other power draws starting with the inverter, which is required to run your AC electrical system. If you use lights, refrigerator, fantastic fans, TVs, power outlets, coffee maker or other appliances, you can kiss using your A/C from solar goodbye. We also didn't discuss your factory A/C inefficiency, or the poor insulation properties of your RV. That's a lot going against you in an RV.

You can pin this comment and come back to it later when all this comes to reality.

 

[Deek Johnson]

Thanks for such a detailed reply...let me review a few times to get my head around the numbers.

But regardless, you're thinking the wire setup looks to be technically correct, right? I'd really like to get those extra 2 panels in series.

Thanks again...

 

[McRod]

Thanks for such a detailed reply...let me review a few times to get my head around the numbers.

But regardless, you're thinking the wire setup looks to be technically correct, right? I'd really like to get those extra 2 panels in series.

Thanks again...

Yes, the wiring looks fine. 4S2P.

I didn't mean to dash your hopes or be so wordy with the math. It is what it is.

Too many people in the RV community have influenced others to believe the standard in RV solar is to be able to run the A/C. It's just not practical in most scenarios.

 

[McRod]

Here is a good real world example of what will happen to your solar in the summer.

This is a 24v system, like yours, with 2400w of fixed solar on the roof of an RV. The weather has been partly cloudy, due to summer monsoon rains in Arizona. I normally generate, on a full sun day about 15kwh of power in a full day.

If you take the best day shown in this picture, 11.25kwh, and divide that by 24 hours, you get an average 469 watts per hour generated by solar. That should make it very clear that 469 watts will not power a system requiring 1200w continuous for 1 device. Even on my best days generating 15kwh, that only equates to 625 watts per hour.

 

[Bobert]

Yes, the wiring looks fine. 4S2P.

I didn't mean to dash your hopes or be so wordy with the math. It is what it is.

Too many people in the RV community have influenced others to believe the standard in RV solar is to be able to run the A/C. It's just not practical in most scenarios.

I have 38’ travel trailer and we do run ac from solar on our rig. We accomplished this by eliminating the rooftop ac unit and installing a mini split. This reduced our needed power in half (our ac unit was 20 years old a newer unit will not likely have as drastic savings). Our trailer is insulated above average. We have 3200 watts of solar on the roof. We have 5k of lifepo4 battery. If we are in full sun we can go indefinitely without the generator. On cloudy day the generator use is drastically reduced because of the solar. Still to run ac with no difficulty we would need 15k of battery and not park in the beautiful forested areas of the north east. Sometimes it’s worth $6 to run the generator a few hours.

 

[McRod]

I have 38’ travel trailer and we do run ac from solar on our rig. We accomplished this by eliminating the rooftop ac unit and installing a mini split. This reduced our needed power in half (our ac unit was 20 years old a newer unit will not likely have as drastic savings). Our trailer is insulated above average. We have 3200 watts of solar on the roof. We have 5k of lifepo4 battery. If we are in full sun we can go indefinitely without the generator. On cloudy day the generator use is drastically reduced because of the solar. Still to run ac with no difficulty we would need 15k of battery and not park in the beautiful forested areas of the north east. Sometimes it’s worth $6 to run the generator a few hours.

Yeah, I live in my four season RV in Arizona, and yes I run an A/C unit. Like you, I no longer use the factory A/C and purchased more efficient aftermarket A/C units. I have invested heavily in insulation, window tint, and minimize power usage during the day when the A/C is on. I have a total of 3000w of solar on 24v with 15kwh (600 ah) of lithium battery power.

That being said, its not enough and its not practical for most RVers. If your not stationary, like I am, just drive to a cooler place. Even with gas prices, it's still cheaper

Your in the NE dealing with 80-90° temps. Not that big of a deal to overcome. I am in Arizona dealing with 100-110° temps EVERY day, and the temp doesn't drop below 100° until 9 or 10 at night. My low temp may be 80° if I am lucky. Usually sit around 85° at sunrise.

Look at this snapshot of my calender for June which I track the daily temp and rain on my property. This year has been average. Last year, in June we had 12 days in a row above 110°

 

[Bobert]

Yeah, I live in my four season RV in Arizona, and yes I run an A/C unit. Like you, I no longer use the factory A/C and purchased more efficient aftermarket A/C units. I have invested heavily in insulation, window tint, and minimize power usage during the day when the A/C is on. I have a total of 3000w of solar on 24v with 15kwh (600 ah) of lithium battery power.

That being said, its not enough and its not practical for most RVers. If your not stationary, like I am, just drive to a cooler place. Even with gas prices, it's still cheaper

Your in the NE dealing with 80-90° temps. Not that big of a deal to overcome. I am in Arizona dealing with 100-110° temps EVERY day, and the temp doesn't drop below 100° until 9 or 10 at night. My low temp may be 80° if I am lucky. Usually sit around 85° at sunrise.

Look at this snapshot of my calender for June which I track the daily temp and rain on my property. This year has been average. Last year, in June we had 12 days in a row above 110°

View attachment 104387

Yes the trouble we have here is no sun much of the time. When it does get hot the humidity tends to approach %90 and it is nearly impossible to sleep (hard to breathe) the mini split does a great job of drying things out and making it easier to breathe once the sun is off our windows (haven’t needed to reflectex them yet) the mini split cools the trailer fine even at 80 degrees overnight ( that has happened once so far this year) during the day we can cool just the living room (144 square feet) but so far it hasn’t been hot enough to be worth it. I rebuilt the trailer to be able to have a comfortable inside temperature at -30 Fahrenheit in the winter and that helps the ac work better also. Our ceilings are only 7’ tall so the cubic feet we must cool is quite a bit less than many units our length. We replaced a 15000 btu unit with a 9000 btu mini split. The mini split cools better than the roof top did I’m glad because the 12,000 btu or larger inside unit would not fit.

 

[Deek Johnson]

Curious...would you mind sharing what mini-split you installed? I was just doing some research and found good reviews on this model (but 12k BTU) but take a look at the energy/watts specification which still looks to be about 1240w if I'm reading that right. https://www.airesconfort.com/specs.html Thx

 

[Bobert]

Curious...would you mind sharing what mini-split you installed? I was just doing some research and found good reviews on this model (but 12k BTU) but take a look at the energy/watts specification which still looks to be about 1240w if I'm reading that right. https://www.airesconfort.com/specs.html Thx

I installed the 9000 btu senville unit on paper it’s super iffy for my application (not enough btus for a campers insulation) but it actually works better than our old 15000 btu roof unit. I had few options as it was the only budget option that would fit in our space. I believe the unit you are looking at has a relatively low seer rating. It might not have an inverter style compressor. Longevity wise there’s no reason to believe it won’t last as long as anything else but it’s energy consumption will be quite a bit higher.