Ram Promaster Forum banner

Roof Configuration For Solar Panels

2960 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
41 - 60 of 104 Posts

· Premium Member
2022 Promaster 2500 159" WB High Roof
Joined
·
150 Posts
Are you running the inverter up front or wired to the back of the van? I am thinking about the electrical in the back and having a line ran through the wall from the battery under the seat to the back. but if I could do it all up front that might make sense too.Thanks for the info on the 12v charging. Doesn't make as much sense as coming straight off the battery now.
I also like the idea of a spare panel. Storing it under the bed doesn't damage it? I think most panels are pretty tough.
Thanks,
Andy
We ran positive and negative cables to the inverter a little over half way between the drivers seat and the wheel well. My Bluetti units are under the front of the bed platform so I can access the ports and the control panel. At this point I am planning on plugging AC appliances directly into the Bluetti. I may wire stand alone AC outlet in the kitchen galley for a hot water heater, but that will probably be it for any AC wiring.
 

· Registered
Promaster 136wb
Joined
·
54 Posts
Discussion Starter · #43 ·
So, some modifications to what I am thinking. Still thinking 350 to 500 solar, either 3x100w or 3x175w. Adding the spare portable panel down the road if I need it. But running a line from the battery box under the drivers seat to the Bluetti in the back not relying on the 12v outlet. Lot easier to run it before I finish the walls than after. If I need it I can add it. I could easily save the cost of the inverter/kill switch for the b2b by cutting out the portable panel or putting one less panel on top.
As far as solar, I still think I can get what I want during most days. I am planning on either being on the road driving, parked at a trailhead hiking to a lake or at a river fishing pretty much 5 days a week. I am not a stationary person. On the weekends I will be refereeing soccer for gas money! Most national parks and soccer parking lots don't have a lot of shade and I also plan on using a solar shower so that needs sunlight too!
I think putting all of that in the back makes the most sense. I like the bench idea behind the drivers seat too...but not sure yet. With the Bluetti being pretty much an all in one solution it doesn't take up much space so the bench might serve a good purpose.
 

· Registered
Van #2 2021 EXT
Joined
·
6,172 Posts
If you are installing an inverter powered by your PM starter battery / alternator, it is best to keep the 12vdc wires as short as possible to the starter battery.

The 12vdc wire length make a huge difference for size of wires.

Then run the 120vac 3-wire to where ever you place your Bluetti. In a van, basically the lengths you have for 120vac are practically irrelevant.

The reason is, the amperage needed in a 12v wire is 1000% more ( 10 X ) than the 120v for the same amount of power.

V * A = W

12v ,,, 1200W / 12V = 100A

120v ,,, 1200W / 120V = 10A


So the Bluetti has an inverter built in & to charge if efficiently from the PM van alternator, you need a 2nd inverter (as noted above). @Boondogger can verify this. So 12vdc to 120vac to whatever the Bluetti charger is, to I assume 48v (or close to it), to 12vdc or 120vac final use.

With 2 inverters, you can use the separate inverter if the van engine is running for 120vac ,,, that might extend your Bluetti energy use a bit.
 

· Premium Member
2022 Promaster 2500 159" WB High Roof
Joined
·
150 Posts
As
If you are installing an inverter powered by your PM starter battery / alternator, it is best to keep the 12vdc wires as short as possible to the starter battery.

The 12vdc wire length make a huge difference for size of wires.

Then run the 120vac 3-wire to where ever you place your Bluetti. In a van, basically the lengths you have for 120vac are practically irrelevant.

The reason is, the amperage needed in a 12v wire is 1000% more ( 10 X ) than the 120v for the same amount of power.

V * A = W

12v ,,, 1200W / 12V = 100A

120v ,,, 1200W / 120V = 10A
As usual, RV is right. We made sure to size the cable based on the length and draw (amps) of the inverter.
 

· Registered
2014 136” HR
Joined
·
7,849 Posts
As far as solar, I still think I can get what I want during most days. I am planning on either being on the road driving, parked at a trailhead hiking to a lake or at a river fishing pretty much 5 days a week. I am not a stationary person.
This yells B2B in addition to solar. I can tell you from years of experience that solar is fickle. Not just clouds or shade, but also these days smoke. Solar collection can suck even when the day looks clear. Since you move a lot, the alternator would be a ready source—and I again stress, it's the alternator you would be using, not the van's battery. B2B connection to the alternator is triggered by an engine-on circuit, plus we have an optional on-off switch on the dash.
 

· Registered
Van #2 2021 EXT
Joined
·
6,172 Posts
As As usual, RV is right. We made sure to size the cable based on the length and draw (amps) of the inverter.
Here is a good calculator;


example;

Font Rectangle Software Parallel Screenshot




The wire run length is return to starter battery terminals ,,, pos & neg ,,, so 7.5 feet length red & white = 15’ length of the circuit.

Voltage drop above example is 5%, but if running @ 2% ( not needed if the PM engine is running IMO), the result of wire size would be much bigger;

Font Rectangle Technology Parallel Electric blue



I design all my “critical electrical loads” to 2% or 1% voltage drop.
 

· Registered
Van #2 2021 EXT
Joined
·
6,172 Posts
This yells B2B in addition to solar. I can tell you from years of experience that solar is fickle. Not just clouds or shade, but also these days smoke. Solar collection can suck even when the day looks clear. Since you move a lot, the alternator would be a ready source—and I again stress, it's the alternator you would be using, not the van's battery. B2B connection to the alternator is triggered by an engine-on circuit, plus we have an optional on-off switch on the dash.
100% 👍

When I joined The Forum in 2019, Solar was “Magical”.🤔

I pondered installing it on my 1st van ,,, but did not want the mileage & heat penalty ,,, I used “Science ,,, not Magic” to guide me in my decision. BTW @GaryBIS did us all a solid in his testing with wind resistant & solar panel setups ,,, We travel much of the time @ 70MPH & 80MPH ,,, being familiar with aerodynamics, I can tell you wind resistance & velocity is a formula jokingly is ,,, Speed = Money Cubed. Gary did his testing @ 60MPH IIRC ,,, So “literally” YMMV. 💸💸💸

We DIYers, really don’t know until we try out our creations & have some road use experiences.
 

· Registered
Van #2 2021 EXT
Joined
·
6,172 Posts
Solar usually allows us to maintain SOC during the day, maybe advance a tad, thus allowing us to boondock longer. B2B has become our primary charging source.
Also, I assume as you are now running lithiums, the solar charging is way more efficient ,,, AGMs near the 100% SOC will increase their “resistance” to all charging ,,, Lithiums ,,, let’r rip & take whatever energy the solar panels can give 👍.

Depending upon the solar charger, the charger can be an excellent maintenance & conditioner for all chemistries.

B2B alternator charging ,,, same thing ,,, lithium just takes the energy fast & is a huge advantage over AGM or FLA nearing full SOC.
 

· Registered
159" 2500 HR Window Van
Joined
·
144 Posts
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 have Bluetti A200Max and its not a direct plug in B2B situation. Firstly the Bluetti products are 48V internal batteries so you would need a 12x48 charger and these are hard to find especially from credible Van/Marine type suppliers such as Victron Stirling etc. Some brave souls have bought cheap chinese 12x48 chargers and got good results but its tricky. (Search on Bluetti or Transit forums). What I did is called the "Orton" method after the inventive first user. I use a Renogy 700W inverter off the van starter battery/alternator and plug the Bluetti 120V charging brick into that. Its inefficient, generating losses and heat in both inverter and charging brick, but it gives you 400W for as long as you are running the vehicle. Plus its fool proof - the brick takes care of any voltage issues and the Bluetti manages its own charging profile.

PS the solar charging can be running in parallel with the inverter/alternator charging giving up to 800W of charge with a 400W solar panel system.

PPS the Bluetti likes higher voltage solar panels so get at least 2 and setup in series. The 200P has a voltage input range of about 40 - 150 so it cannot run on a single panel. The 200Max is more versatile and can do about 10 - 150.
 

· Registered
159" 2500 HR Window Van
Joined
·
144 Posts
@MT Boiler As you can see there are more answers on this forum than a person can digest in a lifetime of travels.... For a sense of sanity look at examples of some builds in the build thread... These are real world operating systems that can provide good ideas.

Good luck with the plans and build!
 

· Premium Member
2014, 138WB, High Roof, Gas, SW MT
Joined
·
3,302 Posts
Ok, this might be a stupid question, but, I am going to ask...If I am pulling DC power from the vehicle battery when I am driving, what prevents my 'power source' from continuing to pull from vehicle battery when I am parked? If most of my power usage is when I am stopped/parked, lights/hotpot/microwave etc. is there a way to just use power source power not vehicle battery power so I can start my vehicle in the morning? To me once you hook it up the power flow is as needed and the 12v cigarette outlet is when I plug it in.
Hi,
That is the job of a DC to DC charger. It looks at the at the voltage of the van battery, and if its above a certain level, it knows the engine is running and its OK to pull power from the van battery/alternator to charge the house battery. It won't discharge your van battery van battery overnight or when the van engine is not running.

One potential problem with the Bluetti style units is that most of them will only accept a few amps charging at 12 volts, so, while the van alternator will happily supply 50 ish amps of house battery charging, but your Bluetti unit may only be able to accept something like 8 amp (varies with type of unit), and this is not enough for effective charging. Its nicer to have a house electrical system that will allow you to recharge your house battery in a couple hours of driving, and this requires a charge rate in the 30 amp area depending on your loads.

Another challenge of these all in one units is that they tend to output only a limited amount of current at 12 volts. In most van conversions, most of the loads are 12 volts - lights, fridge, water pump, furnace, inverter, .. - so its good to have a descent amount juice available at 12 volts. You also should add a 12 volt fuse box in order to safely supply all of the 12 volt loads you have.
This is not to say that you can't use one of these all in one units - many people use them and are happy with them. You just have to work around the two challenges mentioned above.

As was mentioned by @Lolaeliz above is that with the reduction in Lithium Iron Phosphate battery prices, its possible to do a simple house electrical system that will have more capability than the all in one units as the same or lower price.
If this is of interest, here is an example of such a system that is designed to be easy to build and has more than enough capability to meet your needs and can be expanded if your loads grow over time - its cheaper than most of the all in one units. Simple Electrical System...

Gary
 

· Registered
Joined
·
740 Posts
I have Bluetti A200Max and its not a direct plug in B2B situation. Firstly the Bluetti products are 48V internal batteries so you would need a 12x48 charger and these are hard to find especially from credible Van/Marine type suppliers such as Victron Stirling etc. Some brave souls have bought cheap chinese 12x48 chargers and got good results but its tricky. (Search on Bluetti or Transit forums). What I did is called the "Orton" method after the inventive first user. I use a Renogy 700W inverter off the van starter battery/alternator and plug the Bluetti 120V charging brick into that. Its inefficient, generating losses and heat in both inverter and charging brick, but it gives you 400W for as long as you are running the vehicle. Plus its fool proof - the brick takes care of any voltage issues and the Bluetti manages its own charging profile.
Can you go into detail a bit on your "Orton style" inverter setup.

What gauge cables did you use for the 700 watt Renogy inverter?

Gator clamps or terminals on those cables?

Do you have any fuse in the set up?

The Promaster has a 180 amp alternator, thats 2100 watts output I believe, is there a maximum size inverter you would use this way?

You mention things getting HOT, are you concerned about damage to the vans electrical, or are you only cooking the inverter and charging brick etc?

I ask because Im thinking of installing a similar setup with 500 watt inverter..

Thanks!!
 

· Registered
2017 136” HR
Joined
·
937 Posts
Ok, this might be a stupid question, but, I am going to ask...If I am pulling DC power from the vehicle battery when I am driving, what prevents my 'power source' from continuing to pull from vehicle battery when I am parked? If most of my power usage is when I am stopped/parked, lights/hotpot/microwave etc. is there a way to just use power source power not vehicle battery power so I can start my vehicle in the morning? To me once you hook it up the power flow is as needed and the 12v cigarette outlet is when I plug it in.
If you are charging your device from the Promaster stock 12V outlets - they are off when the engine shuts off. Problem solved.
 

· Registered
Promaster 136wb
Joined
·
54 Posts
Discussion Starter · #57 ·
Maybe I am oversimplifiing here but...A power inverter is a couple hundred bucks at the most. Attach one under the driver seat hard wired to the starter battery. The Bluetti comes with an AC power pack that will plus into that and should do all the adjustments the power station needs plus it has a surge protector...correct? So why wouldn't that work. Then I don't have to do anything other than bring the power station up front.
 

· Registered
Van #2 2021 EXT
Joined
·
6,172 Posts
Maybe I am oversimplifiing here but...A power inverter is a couple hundred bucks at the most. Attach one under the driver seat hard wired to the starter battery. The Bluetti comes with an AC power pack that will plus into that and should do all the adjustments the power station needs plus it has a surge protector...correct? So why wouldn't that work. Then I don't have to do anything other than bring the power station up front.
Should Work 👍;

1) Figure out the Bluetii Charger Load “AC Power Pack” (spec’d draw of the charger in watts).
2) Take that & factor i up for the inverter inefficiency ,,, If a decent inverter I think 120% to 130% should ld be close.
3) Install it under the seat or close by where it gets lots of air circulation so it does bot heat up.
4) Size your starter batter to inverter wires (add a fuse on top of the starter battery), calculate amps.
5) “Optional” ,,, Instead of bringing your Bluetti to the inverter, run 3 wire 12gauge & an outlet box to your Blueetti

Regarding #5 above ,,, 120vac so you do not need to work so much about the length of this ,,, you could even use an extension cord (proper gauge).

Some inverters may have a voltage sensing trigger On/Off switch, so the inverter turns on when the engine is running only (fed from an ignition switch circuit).
 

· Registered
Joined
·
740 Posts
Maybe I am oversimplifiing here but...A power inverter is a couple hundred bucks at the most. Attach one under the driver seat hard wired to the starter battery. The Bluetti comes with an AC power pack that will plus into that and should do all the adjustments the power station needs plus it has a surge protector...correct? So why wouldn't that work. Then I don't have to do anything other than bring the power station up front.
You just repeated what Ramvanguy said in a previous post #52, about his set up. It would work.
 
41 - 60 of 104 Posts
Top