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Roof Configuration For Solar Panels

2959 Views 103 Replies 28 Participants Last post by  CanaDave
I just bought my Promaster, 136, 2500, HR. Trying to figure out how to 'arrange' solar panels on the roof.
Definitely adding a Maxxair to the back of the van, centered, I think. I am looking at after market roof racks, I think that would be a lot easier. But, pretty comfortable with Renogy solar panels. I get the 175's I would need at least 2, three would go off the side of the van in a straight line, but provide more power than I would probably need.They are 52.3x26.4. If I go with 100's they are are 41.8 x 20.9 .
With a MaxxAir, Fridge, lights and kitchen, I need 300w on the roof to be close, 400w would be plenty. Trying not to scrimp as this is my first experience and I don't want to run out of juice and prefer to not pull off the vehicle battery unless I am using the 12v for 'emergencies'. Three 175's would be over by about an inch if I lined them up straight across. Four 100's would be the same problem. Not sure how that affects the stealth aspect, but I would like to keep the stealth aspect available if I need to sleep on a public street.
Thoughts on how to arrange to panels? I think putting less holes in the roof by using a rack that clamps to the feet is a good idea but am open to ideas on not only racks but install thoughts.
Thanks
Andy
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Orton style is simply using a smaller inveter off alternator to create 120V and then act as though that is a shore power to charge you battery bank using standard supplied charger (that you use in your house).

Definitely use a larger cable than supplied free with the cheaper inveters. I used a 4 ft marine grade cable - 8 gauge I believe. Size and distance both matter hugely so check manual and a cable calculator. The terminal need to be a ring style and bolted down. Dont use gator clamps or anything that can shake loose.

The positive cable has a fuse at the battery to protect the wiring - I reused the existing 70 amp one from upfitter connection. Most folks are planning to pull around 40 - 60 Amps off the Promaster alternator and it can comfortably handle that all day long.

Things should get warm not hot. Make sure you have air circulation around the inverter and Bluetti - keep the fan areas open. Feel the cable and connections - if any get hot its a sign of problems.

A 500W inverter may be on small size for Bluetti charging since it pulls close to 450W when running and I always prefer a 20% margin or error. That is why I use a 700W.
Thanks for the detailed response, just wanted to fact check it before proceeding with the project!!
 

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I agree with @RamVanGuy. I actually went with the Victron 1200W inverter to add a greater safely margin, plus it should not run as hot at about 50%-60% capacity. May be overkill, but I figured it couldn't hurt.

And my thought process was pretty much the same as @MT Boiler. Another factor was the fact the the footprint of the PPS is more compact than what I would expect from a fully build out battery system with the same capabilities, gaining me space under the garage.
Any idea the max load you've put on that 1200W inverter?

What do typically use the inverter for?

Im assuming you don't have any aftermarket exterior lighting, or large stereos using up the alternators juice..
 

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Any idea the max load you've put on that 1200W inverter?

What do typically use the inverter for?

Im assuming you don't have any aftermarket exterior lighting, or large stereos using up the alternators juice..
Not sure of @BEF081056 case, but here is the Victron chart;

Font Parallel Rectangle Screenshot Electric blue


So the peak for the 1200W is 2400W @ an efficiency of 92%

So you could expect a peak of 2400W / 92% = just over 2600W

Then if operated with engine running only I believe 2600W / say 14.0 volts would be theoretically 186 amps. & if @ 12.0 volts would be 217 amps theoretically.


If @HarryN is correct (& I believe he is), the standy energy of some bigger inverters are the same or less than some smaller ones. The above loads noted were 8W / 5W / 2W ,,, apparently. & the 1600W unit has the same “standby or idle” energy use.

Note 92% “Max Efficiency” ,,, I did not see the “Minimum Efficiency” ,,, verbiage is important.


In the case of the Bluetti;

Rectangle Font Number Circle Screenshot


500W max AC input ,,, and assuming a 85% charger efficiency (I assume as I have no idea) = 588W tgen factor up the inverter efficiency say 90% = 654W

So for me I am working on say a load from the starter battery if about 650W to 700W assumed ,,, divide that by say 14volts if alternator on & providing energy = a draw of assumed about 50amps.

Hey @HarryN ,,, Just looking at the 900W Max solar input ,,, 900W / 15A max is 60volts DC ,,, any magic boxes that can take the 14vdc alternator energy & boost to 60vdc? That is stable & efficient & safe?🤔. Blaa blaa blaa that might be around 75amps to 100amps draw @ 14volts from the alternator?
 

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Any idea the max load you've put on that 1200W inverter?

What do typically use the inverter for?

Im assuming you don't have any aftermarket exterior lighting, or large stereos using up the alternators juice..
[/QUOTE
Any idea the max load you've put on that 1200W inverter?

What do typically use the inverter for?

Im assuming you don't have any aftermarket exterior lighting, or large stereos using up the alternators juice..
I just use the inverter only for charging the AC200P. I haven't measured the current draw going into the inverter, but the charge going into the Bluetti varies between 400 g 500 Watts (I have the 500W charger with the fan.)
 

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Well, no different than camping, living your life, driving cross country or having a day on the lake when something goes wrong. You can either throw a fit and bitch about it, or go with it and make the best of it. Worst case scenario is my beer gets warm (I plan on carrying a cooler as well) my van is dark at night (I will still be sit out under the starts and drink beer from my cooler with ice in it,plus I sleep better with no lights on anyway, because I would rather be outside then sitting in the van) and my fan doesn't work so it is hotter than I expected in the van. I sleep in my underwear outside under the stars because I drank to many beers from the cooler and end up with mosquito bites in to many places to mention!
Things are going to go wrong...tires blow out, alternator dies or something else. I still an living my dream. If the worst thing that happens to me on a 15k journey across the country is the fridge doesn't function for a week or two...well that is a win for me!! I mean half of the world drinks warm beer anyway.
Yeah this is the right attitude, one I try (and occasionally even succeed) to adopt instead of fussing about my SOC and solar shading and etc etc etc.
 

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Discussion Starter · #86 ·
Because you said you will be driving almost daily (like us), you may find it to be a good option once it's connected to your van's alternator. In fact, we still haven't added solar (a

Good luck!
Because you said you will be driving almost daily (like us), you may find it to be a good option once it's connected to your van's alternator. In fact, we still haven't added solar (although we did prewire for it during the build).
I just thought about that! How did you prewire it? Through the roof to the bluetti. Or no hole yet?
 

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Discussion Starter · #87 ·
Just posted a van build plan so everyone knows what I am thinking.

 

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Not sure of @BEF081056 case, but here is the Victron chart;

View attachment 93314

So the peak for the 1200W is 2400W @ an efficiency of 92%

So you could expect a peak of 2400W / 92% = just over 2600W

Then if operated with engine running only I believe 2600W / say 14.0 volts would be theoretically 186 amps. & if @ 12.0 volts would be 217 amps theoretically.


If @HarryN is correct (& I believe he is), the standy energy of some bigger inverters are the same or less than some smaller ones. The above loads noted were 8W / 5W / 2W ,,, apparently. & the 1600W unit has the same “standby or idle” energy use.

Note 92% “Max Efficiency” ,,, I did not see the “Minimum Efficiency” ,,, verbiage is important.


In the case of the Bluetti;

View attachment 93315

500W max AC input ,,, and assuming a 85% charger efficiency (I assume as I have no idea) = 588W tgen factor up the inverter efficiency say 90% = 654W

So for me I am working on say a load from the starter battery if about 650W to 700W assumed ,,, divide that by say 14volts if alternator on & providing energy = a draw of assumed about 50amps.

Hey @HarryN ,,, Just looking at the 900W Max solar input ,,, 900W / 15A max is 60volts DC ,,, any magic boxes that can take the 14vdc alternator energy & boost to 60vdc? That is stable & efficient & safe?🤔. Blaa blaa blaa that might be around 75amps to 100amps draw @ 14volts from the alternator?
Yes, I am a dealer for a one brand of DC - DC converters with ~ similar specs. It is very rugged and has a wide temperature range as you might expect from anything that I am involved with.

Depending on exactly how the BL internal setup "really" operates vs the limited info they provide, it is not so easy to know for sure if it will work or not.

Multi stage voltage / current / voltage power supplies feeding into another power supply is tricky. I have done it, but it took some real testing / experimenting and tweaking. I ended up needing to hire a friend of mine who is an expert in the area to finally pull it off on my test stand. Now it isn't that difficult and I do it on my own systems when needed.

The only way to know for sure is to test it with. I can test a lot of things for people, but not for free.

This DC - DC converter is not cheaper than the consumer grade inverters used in the Orton method, as it is really a heavy duty, commercial (or more) grade, vibration resistant, extended temp range setup. I think that Dave used a Samlex inverter on his van.

I don't think that anyone who has gone down the path of these entry level power systems is going to be interested in this price point to be honest.

I will be at the shop later this week and will see what I have on the shelf but I think that the one I have in stock is a 500 watt model vs the 1 000 watt model.
 

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Yes, I am a dealer for a one brand of DC - DC converters with ~ similar specs. It is very rugged and has a wide temperature range as you might expect from anything that I am involved with.

Depending on exactly how the BL internal setup "really" operates vs the limited info they provide, it is not so easy to know for sure if it will work or not.

Multi stage voltage / current / voltage power supplies feeding into another power supply is tricky. I have done it, but it took some real testing / experimenting and tweaking. I ended up needing to hire a friend of mine who is an expert in the area to finally pull it off on my test stand. Now it isn't that difficult and I do it on my own systems when needed.

The only way to know for sure is to test it with. I can test a lot of things for people, but not for free.

This DC - DC converter is not cheaper than the consumer grade inverters used in the Orton method, as it is really a heavy duty, commercial (or more) grade, vibration resistant, extended temp range setup. I think that Dave used a Samlex inverter on his van.

I don't think that anyone who has gone down the path of these entry level power systems is going to be interested in this price point to be honest.

I will be at the shop later this week and will see what I have on the shelf but I think that the one I have in stock is a 500 watt model vs the 1 000 watt model.
Thanks @HarryN

I kinda had a feeling you would have had experience in things & such ,,, I’m not running out to buy a Bluetti, but had the thought if “the thing” can absorb 900W it would be possible to provide that from the alternator energy with the right equipment & “testing”.

What does that mean for “Bluetti” owners? ,,, You might be able to charge up your completely drained Bluetti in just over 2 hours with the Promaster engine running with the right equipment ,,, providing Bluetti 900W absorption spec is real & not just a sales propaganda ,,, but it probably won’t be inexpensive.
 

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Thanks @HarryN

I kinda had a feeling you would have had experience in things & such ,,, I’m not running out to buy a Bluetti, but had the thought if “the thing” can absorb 900W it would be possible to provide that from the alternator energy with the right equipment & “testing”.

What does that mean for “Bluetti” owners? ,,, You might be able to charge up your completely drained Bluetti in just over 2 hours with the Promaster engine running with the right equipment ,,, providing Bluetti 900W absorption spec is real & not just a sales propaganda ,,, but it probably won’t be inexpensive.
There are a lot of factors involved in charging up a battery pack, and pumping in / out power continuously vs short term are very different.

If you look at their specs:
- Their own external DC input use is 500 watts. If they felt confident that it could handle more, they would have offered a 900 watt solution.

- Their own AC input power is 500 watts. Again - if they felt that it could really handle 900 watts they would have done it.

- The solar panel supplied interface usually puts these units into a different operating mode than a DC power supply operating mode, so it isn't as simple as just attaching DC to a solar input. A solar panel MPPT controller expects a certain type of behavior that is inherent in the IV curve and will be confused by a constant voltage connection.

The other aspect is that relatively few solar installations can supply full power continuously (hours on end ) vs an occasional experience during the very peak of the day. I would be surprised if many people would be able to configure such a setup, so for the most part they can write any spec that they want. 95% of their customers will not attempt this.

Last but not least, I would not attempt to charge their small battery packs at a very fast rate. I am a firm believer in staying with a C/2 rate max for Li based batteries that would be used in a van.

_-
 

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Thanks @HarryN

I kinda had a feeling you would have had experience in things & such ,,, I’m not running out to buy a Bluetti, but had the thought if “the thing” can absorb 900W it would be possible to provide that from the alternator energy with the right equipment & “testing”.

What does that mean for “Bluetti” owners? ,,, You might be able to charge up your completely drained Bluetti in just over 2 hours with the Promaster engine running with the right equipment ,,, providing Bluetti 900W absorption spec is real & not just a sales propaganda ,,, but it probably won’t be inexpensive.
If someone really wants to charge faster, then it is just a matter of buying a setup that can do it and has the fundamental ratings / equipment built in.

As an example, I build this unit mostly for tough conditions use, but the battery pack can in fact charge or discharge at 1200 watts on the DC connection. ( continuously / 24 hrs / day )

The inverter can also output 1100 watts (continuously) - but that assumes that you can also be simultaneously charging it that fast. In reality it only can charge from solar @ 600 watts and 120 vac @ 600 watts (continuously) but again - not that many people will really make the investment in solar to do that in a portable array.

It takes a surprising amount of effort to really obtain 600 watts (real power going into the batteries) from solar for more than 8 hours / day from a portable size array without moving it around. In my test at least, approaching 3 kW of panels in this area and it is still a seasonal thing.



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Thanks for all the notes @HarryN

I just read in another thread by the OP the entire build budget is $5K.

So they offer a DC charge connection “solar” @ 900W max & 15amps max, but that might not work well with 900w / 15amps = 60volts “continuous”. “Sometimes things don’t scale” & it is more complicated than the basic formulas would suggest.

I am not “really” one of those guys BTW ,,, I have no real interest in a Bluetti, but saw the “solar” 900W DC input s performance spec & my mind wandered to what if ? 🤪

Some of my most brilliant ideas I have had comes from that question ,,, “What If”. I am quick to explore & even quicker to drop it once someone like you come to explain “there are issues”. So thank you very much @HarryN !!

That idea kinda reminds me of throwing a car engine into an experimental airplane.

“Richard” aka “Van” once said, “The best conversion I know is to take $8000 and convert it into a good used Lycoming (Aircraft Engine)”.

Literally words of wisdom ,,, “To Live By”.


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Similar to you, with a total $5K conversion budget, probably I would just take 2 each Lifeline AGM batteries, wire them in series to make a 24 volt system.

Buy 24 appliances only. Maybe buy a used fridge.

(edit ) Your Truckfridge 130 is a dual voltage 12 / 24 volt compatible so it is an easy one to use with 24 volt.

24 volt LED light strips are very common. Look at LED supply or super bright leds.



Maybe a propane heater.

No 120 vac at all except for a battery charger.

Just a 12 position fuse block and 1 breaker.

Would be tempted to still do solar. I have some solar charge controllers that I don't use sitting around so those would cost me essentially nothing.

18mm baltic birch on the floor and a floor finish coating.

Paint the sheet metal with a thick coating, perhaps cover it with a low ply carpet. ( yes I am one of those guys )

Carry bottled water and a camping bucket.
 

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I just bought my Promaster, 136, 2500, HR. Trying to figure out how to 'arrange' solar panels on the roof.
Definitely adding a Maxxair to the back of the van, centered, I think. I am looking at after market roof racks, I think that would be a lot easier. But, pretty comfortable with Renogy solar panels. I get the 175's I would need at least 2, three would go off the side of the van in a straight line, but provide more power than I would probably need.They are 52.3x26.4. If I go with 100's they are are 41.8 x 20.9 .
With a MaxxAir, Fridge, lights and kitchen, I need 300w on the roof to be close, 400w would be plenty. Trying not to scrimp as this is my first experience and I don't want to run out of juice and prefer to not pull off the vehicle battery unless I am using the 12v for 'emergencies'. Three 175's would be over by about an inch if I lined them up straight across. Four 100's would be the same problem. Not sure how that affects the stealth aspect, but I would like to keep the stealth aspect available if I need to sleep on a public street.
Thoughts on how to arrange to panels? I think putting less holes in the roof by using a rack that clamps to the feet is a good idea but am open to ideas on not only racks but install thoughts.
Thanks
Andy
check my comments regarding uni strut channels
 

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I just thought about that! How did you prewire it? Through the roof to the bluetti. Or no hole yet?
We ran the solar wires from the area in which we keep the Bluetti (behind driver seat) to the exterior rear camera "box." No holes.

You may want to look at our build although we aren't experts in any of this! 136" Build Thread for Stony VanGo

Here's a pic of our prewire. The link to the actual wires we bought are on our build thread.
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@JohnnyRambles I might be entirely wrong on this and if I am you can definitely point it out But, I actually don't think I would save much money getting everything I would need vs the Bluetti which gives me 200ah and 2000W. The battery alone is probably $700. Add the 1000w pure sine wave inverter, solar capabilities, solar controller, Dc to dc converter, all the output combinations and the other hardware and wires needed to set it all up, create outlets and charging ports, I am just not sure how I match that. Add in the fact I know very little about electricity and power sources, it just make sense to me to buy an all in one that probably costs a little bit more but is far safer and far less space required. adding three batteries to my van is probably twice the space, not to mention all the other hardware. Plus, the times savings is huge for me. I don't have to tinker with it, research it or test it with expensive devices. I get a lot of you guys 'gig' off of creating those but I don't have the electrical experience, tools or testing equipment required to get it all done without spending hours and hours of time researching and than hundreds of dollars for testing devises. If this was fly fishing stuff I would love to spend the hours!! Not to mention the batteries. Lithium makes the most sense but they are expensive. I think I would need two to match the Bluetti. That is $1000 minimum. Or I could go AGM but those you cannot run below 50% and that means three to five of those. At 100 pounds a piece that adds 300 to 500 pounds, which will cut my gas mileage. Going the junk yard battery option adds more batteries and more weight. I plan on driving 15k to 20k a year, so 300 to 500 extra pounds will cost me a bunch in gas...Bluetti 200p is 60 pounds....no way that the total weight for batteries, equipment and hardware is not over 400 pounds if you only have 3 batteries. And I don't think there are three non lithium batteries that total the 200ah and 2000w of the ac200p.
So, I might be wrong on the costs but the space, weight and time savings plus the lack of equipment to adequately test the system for safety purposes points to the all in one.
My Wife and I converted a 159" high top and had a Bluetti AC200 Indigogo Crowd funded unit. It would run our DC lights Maxxair fan, chargers, our Alpicool 12V fridge/freezer and my CPAP for 3-4 days depending on how hard the refrigerator had to work due to outside temps and how much we used the fan. I built a roof rack using the Onaka Roof mounts and adapters and 80/20. Installed 2 Newpowa 240 watt Panels sideways to make the Bluetti's Solar input happy and never had to plug in. We could make 2 cups of coffee in the mornings with 120V knockoff K-cup machine. We always cooked on a camp stove or campfire. We strategically traveled in months that weren't too hot or too cold. It was so much fun. Sold the 1st van cannot wait to build the next one! Should take 25% the time since I kept all my wall and floor templates and I am much wiser to the ways now.
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I am not planning on using a battery bank but a Bluetti 2000w Power Station. Can I plug the battery charger into that??
Another thing to think about before I put the walls on!!
Thanks
I used the jackery 2000 instead of the Bluetti, and I have four Renogy 100 w flex panels mounted on top of my van and the max air fan over my east-west bed in the back. The Renogy 100 w flex panels are narrow enough to be able to have the max air fan between them. I put them lengthwise on the top of the van. I love using a solar generator, because it is less weight than all the batteries, and if I am at home I can take it out and use it for a power failure at the house. Sky Light Window Hood Blue
 

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I just bought my Promaster, 136, 2500, HR. Trying to figure out how to 'arrange' solar panels on the roof.
Definitely adding a Maxxair to the back of the van, centered, I think. I am looking at after market roof racks, I think that would be a lot easier. But, pretty comfortable with Renogy solar panels. I get the 175's I would need at least 2, three would go off the side of the van in a straight line, but provide more power than I would probably need.They are 52.3x26.4. If I go with 100's they are are 41.8 x 20.9 .
With a MaxxAir, Fridge, lights and kitchen, I need 300w on the roof to be close, 400w would be plenty. Trying not to scrimp as this is my first experience and I don't want to run out of juice and prefer to not pull off the vehicle battery unless I am using the 12v for 'emergencies'. Three 175's would be over by about an inch if I lined them up straight across. Four 100's would be the same problem. Not sure how that affects the stealth aspect, but I would like to keep the stealth aspect available if I need to sleep on a public street.
Thoughts on how to arrange to panels? I think putting less holes in the roof by using a rack that clamps to the feet is a good idea but am open to ideas on not only racks but install thoughts.
Thanks
Andy
Check out my Renogy 175 Solar panels review on Amazon. I have 4 of these up on my roof along with a Maxair. Your 136 may not allow 4 175's, but I promise you won't regret getting as many panels up there as you possibly can. Renogy IS the way to go, and I'm pretty sure you can squeeze 4 100 watt units on your roof, and try to get an even number for the most flexibility.
 

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Mine’s a 159, but I fit two 340w Panasonic panels perfectly in the front 2/3 of my Orion Stealth rack and a small deck around my fan in the back 1/3. Covering the whole roof this way also gives me an air gap (permanent shade) for the entire roof of the van to help with temperature control.
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