Am I crazy to put a 1760W solar system on my RV?

[jdcp12065]

My wife and I bought an older RV in rough shape that we are renovating. We saved a bundle on the purchase price so we have money in our budget to spend on a powerful-ish solar system.

Panels:
4x LONGi LR4-72HPH 440Watt
Voc: 48.9, Isc: 11.46 A
Each wired in series with a mate, then the 2 pairs in parallel.
Will be mounted to (manually) tilt with the sun.

All-in-one Alternator + Charge Controller:
Growatt 24V SPF 3000TL

Battery Bank:
6x 100ah SOK 12V Lithium
Each wired in series with a mate, then the 3 pairs in parallel.

Generator Backup:
Honda EU2200i -or- Yamaha EF2400i

Coach power system will not be connected to the engine. A DC-to-DC converter will step down the battery bank for the 12V RV accessories.

What is the consensus on large panels like these? The 4 large panels are much cheaper than lots of 100/200W panels. The panels are less than 1/3rd the price of the batteries.

Will I get a small percentage of the 1700W during the beginning/end hours of daylight or none at all?

Thanks for any advice.

 

[willo]

I'm using LifePO4 cells from china, much better price for that amount of storage but you have to add a BMS to it.
You're looking at effectively 300ah@24v with those. Mine is 560ah@24v for the cost of 1.5-2 of those batteries.

Those panels are around 53lbs each, keep that in mind when considering mounting and tilting.
I keep eyeballing the REC 330s. Biggest issue I have is fitting the things on my roof. There are lots of things that get in the way: A/C, Vents, skylights, etc.
I would get some cardboard and cut it the size of your proposed panels and then do some test placements and take photos.

Don't ignore the potential for engine charging - I added a 240w 12/24 isolated DC-DC charger to my 5th wheel.

I haven't used the growatt, but many here have. I'd look at feedback from owners but I think you'll be fine there.

Finally, you want some sort of shunt based battery monitor - you want to know how much power is going in and out of those cells.

MPPT allows us to generate power a bit sooner than PWM, in general you need enough voltage to get rolling. When you scale up to over 1kw of solar, I think the payoff of MPPT vs PWM is visible. My biggest limiter right now is when my batteries are to cold to charge. My new pack has built in heating to sort that.

 

[Pitownpi]

I obtained Trina 400w panels,80" x 40" doing 3P am also looking at tilting mounting brackets. The only ones I've found wide enough are the 41" Eco-worthy

28" & 41" Length Adjustable Solar Panel Tilt Mounting Brackets | ECO-WORTHY

ECO-WORTHY 28" & 41" Length Adjustable Solar Panel Tilt Mounting Brackets designed for off-grid solar systems, like RV, marine, motor-home, roofs, sheds, etc. Quick assembly with stainless steel fasteners and precise hole placement. Gain up to 25% more solar panel efficiency by tilting your...

www.eco-worthy.com

..and instead of just the pair of brackets, I'd add a 3rd, ie 3 sets of 2 for 2 panels....3 brackets each 400w panel. Other than that, I'm researching just getting the aluminum angle 6061 aluminium and making my own. I'm weight.g the idea to make them so I could tilt in any direction, including along the length.
Have you got any other ideas for mounting and tilting such monster panels?

 

[willo]

Have you got any other ideas for mounting and tilting such monster panels?

Actually, I've been thinking about this.
For my main run of 9 panels, I used unistrut to mount them. However, I created hinge mounts on the outside edge.
If I add a couple perpendicular pieces of unistrut (easy with the brackets/nuts), then I could add a pair of linear actuators to the panels.
(My panels are like 40", in sets of three, so around 120 inches along the top)
A pair of linear actuators to connect the panels to the unistrut mounting and probably another piece to stiffen the edge would do the trick.

I'm still not sure it's worth the effort, flat mounted doesn't produce as much power, but it's one less thing to deal with when I'm pulling out.

 

[Roadtripp]

I’m finding with alternator charging I dont need as much solar. Which is good because my bus is small and won’t fit much solar. I hung one 435 watt panel on the side and one on the roof. It’s working great along with the Kisae DC-DC Charger. But I’m not running a air conditioner. Any sizable loads are only on for a few minutes. Such as my little water heater or induction plate. I suggest install as much solar as you can fit and you won’t regret it. You can also remove some of the vents, antennas, skylights, etc and install more solar. Ive removed everything on two RVs and covered the roof with solar. If you’re rebuilding a older RV it’s something to consider.

 

[willo]

If I were going to continue working on my old RV (gonna sell that sucker) I'd switch to a split A/C unit and go full solar up top as much as possible.

 

[Roadtripp]

Yep, a mini split A/C is what I installed after removing everything from the roof. Was able to fit 2500 watts on the 32 foot Motorhome. Actually it’s a fair amount of weight so if I did it again I’d go with less. It was noticeable while driving. 1760 watts sounds perfect to me. And a DCto DC Charger. There’s some RVers who are running two small window mount A/C units on 1300 watts. The GE units were only $139 each. These window units are what I want to try because my $1000 mini split A/C ran for 3 months then quit. I’d also choose more efficient panels than what I installed. They were all I could find at the time 10 years ago.
Do you think it’s worth putting 1760 watts on a RV you’re planning on selling?? Hope that works out for you. Im wanting to sell mine as I got a smaller more nimble RV. It’s a 1991 so not worth much. And tried selling it a couple times but did not find anyone who valued the solar. They basically wanted the solar for free. I plan to take the 24 volt Outback solar equipment off but leave the panels. I’ll replace the 24 volt inverter with a 12 volt inverter I already have.

 

[HRTKD]

The issues with placing large amounts of solar on the roof of an RV:
1. Weight. Every panel added reduces the cargo capacity of the RV. Can your roof handle the weight?
2. Space. Do you have enough space to put panels of X size on the roof? I used a CAD program to map out my roof and figure out what panels would fit. Don't forget to take into account the additional space required for the mounting brackets. Can you secure the larger panels into the roof truss instead of just into the roof decking which is usually just thin OSB?
3. Install time. Fewer panels means less time to install. However, larger panels often need more mounting brackets than smaller panels. For example, I used 6 brackets on mine instead of the normal four brackets.

 

[Filantrops]

From all videos on youtube i see one common problem when panels are tilted manually - it usually requires person standing on the roof. And roof of RV's, vans or camping trailers are not built for this type of repetative activity. Roofs bend a littlebit every time, that weakens all the seals on the roof and can lead to leakages. I recommend to place panels so that you can adjust the tilt while standing on a ladder or something of that sort.

 

[GSXR1000]

I would consider 24v system to reduce price on SC, wire and so on... then use a 24-12 to your coach battery.. then connect your 12v system to your coach... or not...

 

[Nakinto]

If you can fit those panels on your roof AND have the support, GO FOR IT! I have a 2600W setup with my RV but it is a separate system, ground mount. I have seen up to 4KW systems where the panels retract and extend like wings on either side and some where they have mounted them over every sq foot of the roof and sides. The more solar you have the better, especially if you plan on boondocking during any northern winters! Plus with 1600w, you shouldn't really need to tilt the panels unless you are, again, boondocking in the north. Depending on how you build it, you might want to put an extra frame just for the solar, remember, also, top heavy is your enemy on RVs. Please don't end up on your side.

As for getting power early and late, that is very dependent on the panel orientation. If you have tilt on the panels and aim them east in the morning you will get a lot of power then, but nothing in the evening, if you point them west you will get a lot in the evening but nothing in the morning. When I say "A Lot" I mean more then if you JUST faced them directly south. If you move the panels from East in the morning to West in the evening you will get the best of both worlds but that is best left to a solar tracker, which will increase solar gain by ABOUT 25%, I say about because I have read anything from 15% to 45% and most of the 'scholarly articles' state 30% here are some links as I am being hounded for them.

Beginners' Guide to Solar Trackers: How to Increase Output for Your Home Solar Panel System

solartown.com

Post | Solar FlexRack

solarflexrack.com

Just manually moving them east to west should see a good 10-15% increase but is a LOT of work to do every day, it sucks, trust me, I tried it for a week and said FT!

 

[willo]

This is one reason why I like the higher panel voltage that's accepted by MPPT vs PWM.
PWM controllers - typical input voltage is like 17VDC for a 12V battery and 28VDC for a 24V battery.
If the PV is less

You can start generating usable power a bit earlier in the day =-
Realistically, it's not a huge window, but it's helpful. (Windows snipping tool is a little odd, so forgive the lack of labels here)
It also helps out on marginal solar days. On cloudy days I'm almost always generating some useful charging power.
Blue starts going up at 5:52am and drops at 18:34. I've got a usable voltage generated from 6:23 to 18:07.
This is from today, near Golden, CO.

The blue line is voltage from my panels. The Orange is current being used by my solar controller. (Peak is around 14.6A)
Note that the blue maxes out around 67V, and my battery is a 24v lifepo4 pack. All I really need is like 30v and I have usable charging.

I'll round and suggest that I get around 45 minute or so at the beginning and end of the day of charge time that a PWM system couldn't use.
(I want to call it an hour each way, but I really need to put together a PWM panel to back that up.)

This was a cold day and I'm not heating that pack, so charging was delayed until the batteries warmed up, and charging tailed off when the pack hit 100%. My new pack is getting heaters and will make better use of all that wasted power time.

Upping your solar collection is all about optimizing. One item can be tilting, sure. It's a direct payoff --- if the side of your rig faces the right way.

I'm a flat paneller, and I'm ok with it. Seriously tho, I'm just not into the idea of trekking up on my rubber roof all the time. I'm considering adding some flexible panels since I can walk on them if I need to. Don't forget that you have to access those surfaces to deal with leaks, resealing, A/C maintenance, etc.

 

[rin67630]

Will I get a small percentage of the 1700W during the beginning/end hours of daylight or none at all?

Don't expect that much, and also consider shades.
You probably won't want to park during the summer heat in full sun...
If you have all the panels in one row, having them all in parallel might be more favourable. One panel in full sun + 3 shaded is better than having a pair in shade and another pair half shaded.
During bad heavy cloudy days, to get only 5% of the nominal power is not unusual.

 

[HRTKD]

I'm a flat paneller, and I'm ok with it. Seriously tho, I'm just not into the idea of trekking up on my rubber roof all the time. I'm considering adding some flexible panels since I can walk on them if I need to. Don't forget that you have to access those surfaces to deal with leaks, resealing, A/C maintenance, etc.

Welcome to the Flat Panel Society. You're member #2.

 

[Screwball]

Welcome to the Flat Panel Society. You're member #2.

I joined the flatpanelsociety as well ...
On my previous toyhauler I put a lot of work into a two-sided tilting mount ... and in the 5 years of fulltime living i did not tilt them a single time ? ... who wants to crawl up there and do all that extra work when the campfire is on and the cold beer in the fridge is calling your name ?!?
On my new trailer I figured I need ~1000w for day to day, added an extra 500w for the residential fridge and another 500w for compensating flat mount losses = 2000w of maintenance/worry free fixed flat panels.
8x 250w Trinas, in 2 groups of 2s2p to better deal with partial shading

 

[HRTKD]

Had to update my signature with the Flat Panel Society line.

 

[fratermus]

What is the consensus on large panels like these? The 4 large panels are much cheaper than lots of 100/200W panels.

As you've found, high-wattage, high-voltage panels tend to be much cheaper than their smaller counterparts. I recommend them for everyone who has the need, the room, and the ability to get them into place. I recently wrestled 250w panels up the ladder by myself and it wasn't as much fun as it sounds.

Will I get a small percentage of the 1700W during the beginning/end hours of daylight or none at all?

A little, but there's not much there to harvest. I get 0.5-3% of rated output at dawn/dusk when there is only indirect light on the panels. That'd be about 16-47w for your proposed array. Here's a test where I got ~0.8% of rated at daybreak from higher-voltage panels where nominal 12v ones likely wouldn't have reached Vbatt.

This morning (7,000' altitude, ~40deg F, flat 750w poly string) I was getting 2.6% of rated (~20w) while the sun was fully hidden behind the trees/hill. The sun started to show and output jumped to 5% (50w), then quickly to 30% of rated (230w) and climbing until Vabs was achieved.

For comparison purposes, I typically see ~15% of rated under full overcast (no shadows on the ground), 8-10% in dark full overcast, and ~25% in bright full overcast (can't see where the sun is but the sky is bright).

 

[willo]

Here, this'll give you an idea. This is today, time is MST if you want to compare against sunrise. Location is between Golden and Boulder, CO.
Edit: This is 12x rich solar 100s, wired in a 3s4p config, so I generally see 60-70 volts in good light.
I'm probably down in power generation a little bit today, as I have the front of the camper jacked up an extra couple of feed to save my back while working in the battery bay.

 

[rickst29]

Had to update my signature with the Flat Panel Society line.

Can I join the society? All of my installations have been "flat" on the RV roofs.

 

[HRTKD]

Can I join the society? All of my installations have been "flat" on the RV roofs.

Go to the link at the top of the page where your name is displayed, click on that and then go to "Signature" to edit your signature.