Proposed 24v Motorhome Solar System

[SunRunLandYacht]

Proposed 24v Solar System for fulltime retired explorer couple with 35’ 50amp Motorhome RV (mh). I think this setup will handle the majority of our living environments or we will adapt &/or change altitude. I am new to solar and would very much appreciate constructive advice and suggestions. I want to do this right, the first time and feel safe sleeping with it.



Solar Panels = 2800w: 7- 400w Trina or other 40”x 80” 45v @ 9.74a solar panels. Six mounted above roof of the mh and one deployable on roof of tow vehicle. All panels will be wired in parallel (45v @ 58 to 68amps) to minimize effects of shading at, available boondock campsites in National Parks or other. Solar is maxed out so usage will be adjusted as needed.



24v Solar Controller = Victron 150/100 or other that will handle the 68amp input with safety margin. Are there better alternatives?



Battery Bank = 2 – Big Battery 24v 170ah Power Blocks in parallel = 8kWh already ordered and shipping 11-20-20. Might add another Power Block or cut consumption as usage dictates.



Inverter / Chargers = 2-Victron (or ?) 24v/3000w inverter/70a charger MultiPlus (have a 2-way transfer switch between shore power and Onan GenSet) or maybe MultiPlus Quattro (at times will be plugged into full or limited shore power). Believe these can be wired single phase, with parallel communication to second unit that will turn on and off as 120v usage exceeds output of single unit or I can install them in split phase if determined to be best. These units are very efficient and I have read that alternatives are less efficient, noisy fans and have other issues. I think I may need 2 Current Surge Limiters for the inverters and 2 micro starts for roof air-conditioners (intend only limited use of one, if necessary)? The only drawback to Victron equipment, I see, is the cost but I do like the inter communication and monitoring between the equipment components. Please advise as I am without a money tree.



Orion (?) 100amp 24v DC to 12v DC converter for house lights, h2o pump, etc.



I believe the alternator on my Cummings diesel is currently used to provide 12v DC operating circuits, charge the two flooded start and 2 AGM house batteries, etc. The AGMs are currently used to power a 1kw Xantex Inverter for limited overnight power and to keep the ice maker going while traveling and will be removed along with a newish 70amp 12v Progressive Dynamics converter. I think I will be able to install a small 12v DC to 24v DC step-up inverter ?/ converter to provide limited charge to the LiFePo4 battery bank enroute. I do not want to damage my alternator and can charge bank with generator + dual 70amp Victron chargers; if absolutely necessary. I hope this system can, otherwise, make the GenSet useless and removable.



Monitoring: Have TR-16 with 500amp shunt (sampler) on AGM negative now. Will probably be installing a Victron BMV-712 battery monitor with bluetooth but need to research more and look into needs vs wants and other options like the Victron Color Control, Octo GX computer and what you suggest. I want to be aware of system condition and safety, always.



I know I have asked a lot and there are many things I have not covered and questions not asked, so your help and suggestions will be appreciated. Much thanks in advance and stay safe! Mike



​

 

[JDTravels]

Hello and welcome to the wonderful world of solar powered wandering. (Sorry for the book below....)
I was wondering if you have a chance to do a power audit to estimate your average daily needs?
I found this to be an invaluable tool during my planning stage.
I really like the Victron for the integration and the sealed ckt boards. Being able to custom configure the system was also a huge plus.

We currently live fulltime (3+ years) in a 40 FT DP that I have converted to all electric.
Rig: induction cooktop, replaced 2 roof air conditioners (15K each) with 1 mini split(240V) 12K, residential fridge(21 cu ft), convection/microwave, stainless steel electric only water heater, 2 desktop computers, and a large screen tv.
Solar/electrical: 1800W of panels(2 strings/3panels), 2 Victron Quattros(3000W/48V) splitphase, BMV712, 150/35 solar controller, Color control GX(for wife), 30A DC-DC converter (48V to 12V). 100 AMP(48V) hours of Fortune Lithium cells in 2 pack config. 200 Amp total battery size.
I went for the higher voltage less current from the solar panels to reduce the wire size and heating/loss and allow me to save money by going to a smaller controller. I have disconnected the alternator from the house battery system completely...not needed with all the solar. I would recommend that you connect a trickle charger to the chassis battery once in a while to keep them happy. (I use a old Sears battery charger plugged into 110V off the house system)

We don't usually camp in the trees and seek clear skies for solar and satellite. We are TV/news junkies. Plus clear LOS for cell booster better performance.
We have been happy thus far with the overall performance of the system. We have had some times where I wish we had a bigger battery on really hot days when running the air into the evening. 105 days in AZ without a breeze. We have tripped the overtemp on one of the inverters in the summer heat and large load. On the other end, in the winter running the heat pump when we do not harvest as much solar, I have to run the genny for a couple hours about every 3 days to bring the batteries back up. I have been testing a propane catalytic heater (Wave 6) and have been very happy with it. One thing to note is that when you are using a configuration split phase with the Victron Quattro, you cannot use the auto sensing mode. Thus they will have to stay on all the time.

We are moving to a new rig (trailer) so we can go further off the beaten path... I will be keeping the propane on the new rig this time and the Wave 6 heater to supplement the furnace (don't like furnace fan noise). I will install another mini split but the wall mounted 110V version this time. I will also install another residential fridge (10 cu ft). They do not have to be perfectly level to operate and run just fine going down the road. I like my ice cream frozen
The new setup will include:
272AH Lishen cells configured for 24V, 2 packs, Victron smart shunt, color control GX, (1) 3000/24V Multiplus, 150/60 controller and 4 400W Trina panels setup in 2 strings.
I went for 24V this time because the parts are a little cheaper and I can get replacements at most RV shops/dealers in an emergency if needed. Plus I will be able to keep my cables at about the same size because the equipment will be much closer together this time.
I would ot cheap out on the cables in my designs... in my opinion it is worth a few dollar more to go with slightly larger, (upsize one) good grade multi stranded welding cable. There are some very good sizing tools to perform your audit...some are available in spreadsheets. Don't forget to factor in some fudge..
Good luck in your design and install.....
P.S. I will still have a portable genny in the new rig...just in case.

 

[JDTravels]

I was just going over my reply and realized I did not include a couple of things:
In an RV the "50A" covers everything in the RV air, a/c loads, dc loads. I think the DC-DC converter could be a lot smaller since it will only be used to power the dc loads in the coach. I also wanted to clarify that my DC converter is to convert 48V battery to 12V loads only (lights, water pump etc.). It is not for charging the chassis battery.
In my rig the genny out is 110V single phase. It feeds the inverter that in turn charges the battery. In your case I think it will be connected to the charger.
My alternator(generator on some diesels) is used to charge the chassis battery.
I created a system/wiring schematic to help keep it straight in my head.. I used Libre office draw just because of cost..(free)
I am attaching a sample of the new rig drawing..not final yet..

good luck sir

 

[HRTKD]

That Victron solar charge controller will work. It will have a good enough safety margin. I'm not convinced that you need to go 6p with the panels but you know more about where you camp than I do. I rarely am in campgrounds, so I can pick my spot for maximum sun exposure.

I went with Victron components where I could. I'm quite satisfied with it.

What are you doing with the single panel on the trailer?

 

[SunRunLandYacht]

Thanks for the inputs JDTRAVELS and HRTKD.

Admire both of you for your solar systems, knowledge and boondocking experience. I have spent some time in Yellowstone, Quartzsite and other boondocking situations and want to be more comfortable and a less noisy neighbor. I used propane with the frig and h2o heater and watched videos on the 17” laptop but want a better experience.

I am, kind of, approaching this project from a reverse engineering point of view. In researching solar I read all of the upgrades people are doing to their systems because of energy hunger. I fully agree with the logic of starting with the energy audit to judge your needs and building a system to meet it. Based on my experience, I am going to max out the solar panels I can have on the roof of my motorhome (6) and one additional panel attached to the roof rack of my tow vehicle. I can plug it in, place in full sun and this is my max of panels. I will adjust my energy needs to the system.

JD I have a Wave 6 up front between the drivers and passengers seat facing towards the rear and a wave 3 in the bedroom, on a swing out tv wall mount. Hands down this, in my humble opinion, the most efficient way to heat. Keep it covered between uses or dust will kill the burner material and you will have to replace the heater.

As to your setup: Love the mini split and wish I had time for that mod but my roof airs are newish so I will try the micro starts and see how it goes. Have only used both roof airs once or twice and do not want to be where I need even one. Agree with you on the hard ice cream and may do the Samsung drop-in to replace my 4 door absorption frig in the future. Fortune cells...looked into that (a little) after Will Prowse’s (My Solar Hero) review but the cost I found per ah for raw cells was more than the assembled Power Blocks and he spoke highly of the 12v model in his review. I will see how the 8kWh bank works out and maybe add one more. I will definitely do the induction (X-mas) and am looking at the 2 burner True Induction unit.

Would be interested in reasoning behind downsizing to one 24v Victron 3k while increasing to 13kWh bank. How did you find the efficiency with the 2 48v 3k in split phase use? I still have to look into the monitoring setup, believe the BMV-712 with Bluetooth and smart shunt (? amps) is a minimum requirement if I want to internet monitor and manage the system. What does the Color Control GX bring to the system other than the color display?​

I will add up DC requirements for 12v lights, h2o pump, Lorex security system, etc. I think you are right 100 amps is probably excessive for the Orion 24v to 12v converter. Good point about split phase and auto sensing!

I will definitely not cheap-out on the other materials & supplies needed and will design in sufficient to liberal safety margins. I will look at your elec. diagram and when I have enough information try to do the same.

Hope I have addressed everything in this book chapter.

Much Thanks and Stay Safe,​

Mike

 

[HaldorEE]

Proposed 24v Solar System for fulltime retired explorer couple with 35’ 50amp Motorhome RV (mh). I think this setup will handle the majority of our living environments or we will adapt &/or change altitude. I am new to solar and would very much appreciate constructive advice and suggestions. I want to do this right, the first time and feel safe sleeping with it.



Solar Panels = 2800w: 7- 400w Trina or other 40”x 80” 45v @ 9.74a solar panels. Six mounted above roof of the mh and one deployable on roof of tow vehicle. All panels will be wired in parallel (45v @ 58 to 68amps) to minimize effects of shading at, available boondock campsites in National Parks or other. Solar is maxed out so usage will be adjusted as needed.



24v Solar Controller = Victron 150/100 or other that will handle the 68amp input with safety margin. Are there better alternatives?



Battery Bank = 2 – Big Battery 24v 170ah Power Blocks in parallel = 8kWh already ordered and shipping 11-20-20. Might add another Power Block or cut consumption as usage dictates.



Inverter / Chargers = 2-Victron (or ?) 24v/3000w inverter/70a charger MultiPlus (have a 2-way transfer switch between shore power and Onan GenSet) or maybe MultiPlus Quattro (at times will be plugged into full or limited shore power). Believe these can be wired single phase, with parallel communication to second unit that will turn on and off as 120v usage exceeds output of single unit or I can install them in split phase if determined to be best. These units are very efficient and I have read that alternatives are less efficient, noisy fans and have other issues. I think I may need 2 Current Surge Limiters for the inverters and 2 micro starts for roof air-conditioners (intend only limited use of one, if necessary)? The only drawback to Victron equipment, I see, is the cost but I do like the inter communication and monitoring between the equipment components. Please advise as I am without a money tree.



Orion (?) 100amp 24v DC to 12v DC converter for house lights, h2o pump, etc.



I believe the alternator on my Cummings diesel is currently used to provide 12v DC operating circuits, charge the two flooded start and 2 AGM house batteries, etc. The AGMs are currently used to power a 1kw Xantex Inverter for limited overnight power and to keep the ice maker going while traveling and will be removed along with a newish 70amp 12v Progressive Dynamics converter. I think I will be able to install a small 12v DC to 24v DC step-up inverter ?/ converter to provide limited charge to the LiFePo4 battery bank enroute. I do not want to damage my alternator and can charge bank with generator + dual 70amp Victron chargers; if absolutely necessary. I hope this system can, otherwise, make the GenSet useless and removable.



Monitoring: Have TR-16 with 500amp shunt (sampler) on AGM negative now. Will probably be installing a Victron BMV-712 battery monitor with bluetooth but need to research more and look into needs vs wants and other options like the Victron Color Control, Octo GX computer and what you suggest. I want to be aware of system condition and safety, always.



I know I have asked a lot and there are many things I have not covered and questions not asked, so your help and suggestions will be appreciated. Much thanks in advance and stay safe! Mike



​

One comment is watch out for the max current limit of an MC4 connector if you are using MC4 branch connectors. Like these:

Amazon.com: Renogy Solar MC4Y2 Branch Connectors MMMF+FFFM Pair, Multicolor: Garden & Outdoor

Amazon.com: Renogy Solar MC4Y2 Branch Connectors MMMF+FFFM Pair, Multicolor: Garden & Outdoor

www.amazon.com

Despite the fact you can buy 4 into 1 MC4 Branch connectors, but I wouldn't go above 3 into 1 with these panels. An MC4 connector max current is only 30A and 4 of these panels into 1 would definitely overload it.

My preference would be to configure the 6 panels as 3 parallel strings of 2 panels in series. That is because I hate using more than 75% of a connectors current rating (things used at their max tend not to last as long). But doing that would preclude you being able to use the ground mounted panel unless you add a dedicated solar charge controller for the ground panel.

 

[SunRunLandYacht]

One comment is watch out for the max current limit of an MC4 connector if you are using MC4 branch connectors. Like these:

Amazon.com: Renogy Solar MC4Y2 Branch Connectors MMMF+FFFM Pair, Multicolor: Garden & Outdoor

Amazon.com: Renogy Solar MC4Y2 Branch Connectors MMMF+FFFM Pair, Multicolor: Garden & Outdoor

www.amazon.com

Despite the fact you can buy 4 into 1 MC4 Branch connectors, but I wouldn't go above 3 into 1 with these panels. An MC4 connector max current is only 30A and 4 of these panels into 1 would definitely overload it.

My preference would be to configure the 6 panels as 3 parallel strings of 2 panels in series. That is because I hate using more than 75% of a connectors current rating (things used at their max tend not to last as long). But doing that would preclude you being able to use the ground mounted panel unless you add a dedicated solar charge controller for the ground panel.

HaldorEE, thanks for the heads up. Because of my boondocking experiences, I have had to set up camp based on space available and some were shaded at times. That is why I want to max out the solar panel square footage to provide best possible solar input to the controller and thus the battery bank under less than ideal shaded conditions. In ideal conditions the down side is the battery bank will be charged sooner. Issues with unavoidable shading are why I want to wire in parallel. If there is additional information on series vs parallel, other than smaller wire gauge, please enlighten me. The 400w panel meets voltage requirements for a 24v bank and does not require series wiring. Would running them in sets 2 to the roof mounted combiner box take care of the over amp MC4 issue.​

Another good point about the ground deployed panel. I just assumed, (yes I have been bit numerous times.), that there would be a way to input it to the system with an extension cord type setup. I think the braided welding cable from the combiner box to the controller will have to be a fairly large gauge for the ?60 amps it will carry but it will be about 10’ to the controller. Can the two solar inputs be combined in some configuration or would there have to be a second small controller added to use the seventh panel?

I am in the research stage and will diagram all components, breakers, fuses and wire gauges before installation begins. I would like to present it to to be critiqued by more knowledgeable eyes and minds in this forum. The further I dig into this solar system setup the more minutiae I find that has to be factored in.

Thanks again.​

 

[HRTKD]

With regard to the ground deployed panels, I did that in my system. 640 watts on the roof and the same on the ground. I chose to use two solar charge controllers, one for each set of panels. I did it that way in part to simplify the wiring - they are distinct systems - and also because all four panels together on one controller would have exceeded the capacity of the Victron 100/50 solar charge controller. Yes, I could have moved up to a bigger controller, but the redundancy of two identical controllers was a nice benefit.

The downside of ground deployed panels is that you have to store them. Figure that out before you go down that path.

The 10 gauge PV wire I used on the roof is the same wire I used to create an line from the side of the trailer to the ground deployed panels. My line is only 25' at this time, but I plan to create a second 25' line for those times where the first line isn't enough.

 

[HaldorEE]

HaldorEE, thanks for the heads up. Because of my boondocking experiences, I have had to set up camp based on space available and some were shaded at times. That is why I want to max out the solar panel square footage to provide best possible solar input to the controller and thus the battery bank under less than ideal shaded conditions. In ideal conditions the down side is the battery bank will be charged sooner. Issues with unavoidable shading are why I want to wire in parallel. If there is additional information on series vs parallel, other than smaller wire gauge, please enlighten me. The 400w panel meets voltage requirements for a 24v bank and does not require series wiring. Would running them in sets 2 to the roof mounted combiner box take care of the over amp MC4 issue.​

Another good point about the ground deployed panel. I just assumed, (yes I have been bit numerous times.), that there would be a way to input it to the system with an extension cord type setup. I think the braided welding cable from the combiner box to the controller will have to be a fairly large gauge for the ?60 amps it will carry but it will be about 10’ to the controller. Can the two solar inputs be combined in some configuration or would there have to be a second small controller added to use the seventh panel?

I am in the research stage and will diagram all components, breakers, fuses and wire gauges before installation begins. I would like to present it to to be critiqued by more knowledgeable eyes and minds in this forum. The further I dig into this solar system setup the more minutiae I find that has to be factored in.

Thanks again.​

Basically just wiring advantages. In my much smaller system I have one 300W panel on the roof and if I want to add a second panel it would be added in series with the first one. That is why my SCC is rated for 100V even though I am only using a "24V" panel.

One thing that could simplify your system is to go with a 48V battery system. That would let you use a smaller SCC (150/50) and make all of your wiring lighter, cheaper and easier to install. My system only has a 2000W inverter and I am using 24V. My opinion is that any time you go bigger than a 3000W inverter you should at least consider using a 48V system. Especially if you are using 16 cells in a 2P8S configuration to create your 24V battery.

On components. I am a fan of Blue Sea, they make yachting electrical equipment. And I really like PKYS as a vendor. That is who I have been buying components from. Paul Kennedy is the PK part of PKYS (Paul Kennedy Yacht Services). He is a very knowledgeable electrical system designer and installer. He is a very good choice if you decide to go with a Victron based system.

PKYS INC Marine Electrical Systems Experts

You can get custom electrical control panels from Blue Seas which are a very cool solution. Probably better than you would see in high end RVs.e

360 Series Modular Panel System by Blue Sea Systems

Blue Sea Systems Systems Custom Made Circuit Breaker Panel

 

[HaldorEE]

With regard to the ground deployed panels, I did that in my system. 640 watts on the roof and the same on the ground. I chose to use two solar charge controllers, one for each set of panels. I did it that way in part to simplify the wiring - they are distinct systems - and also because all four panels together on one controller would have exceeded the capacity of the Victron 100/50 solar charge controller. Yes, I could have moved up to a bigger controller, but the redundancy of two identical controllers was a nice benefit.

The downside of ground deployed panels is that you have to store them. Figure that out before you go down that path.

The 10 gauge PV wire I used on the roof is the same wire I used to create an line from the side of the trailer to the ground deployed panels. My line is only 25' at this time, but I plan to create a second 25' line for those times where the first line isn't enough.

Higher voltage (series) is much better if you are going to be running cables any distance since it reduces resistive losses in the wiring. Very smart.

 

[SunRunLandYacht]

With regard to the ground deployed panels, I did that in my system. 640 watts on the roof and the same on the ground. I chose to use two solar charge controllers, one for each set of panels. I did it that way in part to simplify the wiring - they are distinct systems - and also because all four panels together on one controller would have exceeded the capacity of the Victron 100/50 solar charge controller. Yes, I could have moved up to a bigger controller, but the redundancy of two identical controllers was a nice benefit.

The downside of ground deployed panels is that you have to store them. Figure that out before you go down that path.

The 10 gauge PV wire I used on the roof is the same wire I used to create an line from the side of the trailer to the ground deployed panels. My line is only 25' at this time, but I plan to create a second 25' line for those times where the first line isn't enough.

HRTKD thanks for the input.

I need to clarify my concept for “ground deployment” for the 7th panel, as it will differ from the norm. I am going to build an aluminum roof rack with tilt to mount to the roof of my minivan semi-permanently. The minivan already has threaded attachment points that can handle a 150# load. It will be like a rack mounted solar panel with wheels. All I have to do is park it in the sun, tilt and plug in, voila, an extra 400w potential of tuned solar power input. Cleanup is a snap... unplug and go. (And yes I will tell all of the inquirers at the Walmart parking lot that YES the minivan IS solar powered- hummer!)

I agree with you about the fuzzy factor of a redundant second controllers, and that is a clear alternative. That’s why I am looking at two 3k Victron inverters rather than one 5k, beside the extra 1k of capacity.



I would really like to know (input please) if there is a good safe method to simply plug the 7th panel into the Victron 150/100 controller I am currently focused on? How would/could or should I combine the large gauge welding cable 10' +/- carrying 40 something volts @ 58ish amps from the combiner box on the roof of the motorhome and a 10 gauge (?) extension cord from the 7th deployed panel???



Thanks again Mike



​

 

[HRTKD]

The minivan is your toad?

The only way I see to wire the single panel into a solar charge control that will already have other panels wired into it is to make all the panels parallel. Put an SAE connector on the side of the motorhome and plug the single panel into that. From the SAE connector, the wire would go into a combiner box and from there into the solar charge controller.

I'm not sure the single panel is worth the hassle, but that's a novel way to add a panel.

 

[SunRunLandYacht]

Basically just wiring advantages. In my much smaller system I have one 300W panel on the roof and if I want to add a second panel it would be added in series with the first one. That is why my SCC is rated for 100V even though I am only using a "24V" panel.

One thing that could simplify your system is to go with a 48V battery system. That would let you use a smaller SCC (150/50) and make all of your wiring lighter, cheaper and easier to install. My system only has a 2000W inverter and I am using 24V. My opinion is that any time you go bigger than a 3000W inverter you should at least consider using a 48V system. Especially if you are using 16 cells in a 2P8S configuration to create your 24V battery.

On components. I am a fan of Blue Sea, they make yachting electrical equipment. And I really like PKYS as a vendor. That is who I have been buying components from. Paul Kennedy is the PK part of PKYS (Paul Kennedy Yacht Services). He is a very knowledgeable electrical system designer and installer. He is a very good choice if you decide to go with a Victron based system.

PKYS INC Marine Electrical Systems Experts

You can get custom electrical control panels from Blue Seas which are a very cool solution. Probably better than you would see in high end RVs.e

360 Series Modular Panel System by Blue Sea Systems

Blue Sea Systems Systems Custom Made Circuit Breaker Panel

HaldorEE Thank you very much for the interest and willingness to help a Newbie!

I referenced these design limits when I started making notes some time ago: 12v = 2000w inverter, 24v = 4000w inverter and 48v = 8000w inverter. People, if that’s not right let me know. I keep in mind that my two 24v banks can easily become 48v...and I am at the research stage.

Definitely want to look at Blue Sea as I have seen them in several systems on youtube; thanks for the info.

I have considered the wiring and 48v advantages. I am sitting about 20’ from my nephew’s 48v fixed base solar system. We have had discussions in length about these topics. The two big design consideration I have accepted are: (1) SHADING - If since there is the potential for shading of the motorhome roof in an only camp space available situation in one of the National Parks I frequent or other, according to Will Prowse (My Solar Hero) and what other references I could find, that shading severely effects solar panel production on panels wired in series. So for that reason I am wiring in parallel and paying the price of good quality larger gauge welding wire for the 10’ +/- from the roof mounted combiner box to the Victron 150/100 SCC input. Would appreciate input as to how to combine the roof pv input with input from an additional ground deployed 400w panel??? I know that I can do two SCCs.

(2) MAX SYSTEM VOLTAGE OF PARALLEL PANELS - With a non series wired solar panel configuration the approximate 40+v of these 40”x80” panels will support a 24v battery system but that is the max, if not in series. I am not considering panels that might be borderline for 36v or other potentially exotic system, I want to stay as close to mainstream as I can. I know that the future probably holds 120v ac panels but we are not there now. I also like the safety of a 24v system again according to My Solar Hero(WP). Therefore I am going with a 24v system. Believe me, I would prefer to get as close to the voltage output of the inverter (120v) as I could considering efficiency but with these two limiting factors I think I am dead on target. Please, to those among you with the knowledge, tell me where I am wrong and or offer suggestions?

Thanks again HaldorEE and Stay Safe!​

 

[HaldorEE]

HaldorEE Thank you very much for the interest and willingness to help a Newbie!

I referenced these design limits when I started making notes some time ago: 12v = 2000w inverter, 24v = 4000w inverter and 48v = 8000w inverter. People, if that’s not right let me know. I keep in mind that my two 24v banks can easily become 48v...and I am at the research stage.

Definitely want to look at Blue Sea as I have seen them in several systems on youtube; thanks for the info.

I have considered the wiring and 48v advantages. I am sitting about 20’ from my nephew’s 48v fixed base solar system. We have had discussions in length about these topics. The two big design consideration I have accepted are: (1) SHADING - If since there is the potential for shading of the motorhome roof in an only camp space available situation in one of the National Parks I frequent or other, according to Will Prowse (My Solar Hero) and what other references I could find, that shading severely effects solar panel production on panels wired in series. So for that reason I am wiring in parallel and paying the price of good quality larger gauge welding wire for the 10’ +/- from the roof mounted combiner box to the Victron 150/100 SCC input. Would appreciate input as to how to combine the roof pv input with input from an additional ground deployed 400w panel??? I know that I can do two SCCs.

(2) MAX SYSTEM VOLTAGE OF PARALLEL PANELS - With a non series wired solar panel configuration the approximate 40+v of these 40”x80” panels will support a 24v battery system but that is the max, if not in series. I am not considering panels that might be borderline for 36v or other potentially exotic system, I want to stay as close to mainstream as I can. I know that the future probably holds 120v ac panels but we are not there now. I also like the safety of a 24v system again according to My Solar Hero(WP). Therefore I am going with a 24v system. Believe me, I would prefer to get as close to the voltage output of the inverter (120v) as I could considering efficiency but with these two limiting factors I think I am dead on target. Please, to those among you with the knowledge, tell me where I am wrong and or offer suggestions?

Thanks again HaldorEE and Stay Safe!​

Your thinking is sound. I am an EE so I tend to be very conservative in my designs. That is why my thresholds are <2000W = 12V, 2000W to 3000W = 24V, above 3000W = 48V. 4/0 AWG wire is not only heavy and expensive, but it is really hard to horse into tight quarters. I am able to comfortably use 1/0 AWG wires with my 24V, 2000W inverter. I could use 12V, but then I would be using 2/0 AWG wires.

 

[HaldorEE]

I also never use anything to its rated capacity. If I need 20 A, then whatever it is will be rated for 30A.

 

[Hedges]

(1) SHADING - If since there is the potential for shading of the motorhome roof in an only camp space available situation in one of the National Parks I frequent or other, according to Will Prowse (My Solar Hero) and what other references I could find, that shading severely effects solar panel production on panels wired in series. So for that reason I am wiring in parallel and paying the price of good quality larger gauge welding wire​

I'm not at all convinced that series wired panels experience any penalty under partial shading. So long as bypass diodes work, can carry Imp. (have heard some can not.)

Let's assume each panel has 3 bypass diodes.
If shading completely obscures one cell, one third of a panel is lost. In parallel configuration, good chance only the remaining panels deliver power.
In series configuration, all unshaded panels and the 2/3 of the partially shaded panel deliver full voltage and current. Only 1/3 of one panel's production is lost.

Solar edge will present arguments why their per-panel optimizer is better when a cell is partially shaded. But I say shadows move, and most of the time you have one or more whole cells shaded.

I use high voltage string inverters at home, and have experimented with shading one panel in a 9s2P array. Power production only decreased about 1/18th. Series/parallel is fine with slight amount of shading, but would have a penalty if one string had considerable amount of shading (as I argued regarding parallel panels.)

Now a benefit of parallel panels or strings, if panels are tilted, is you can cram more watts of panels on a given charge controller. Oriented differently (only if you tilt panels on the roof, of course), you get lower peak watts but spread over more hours.

 

[SunRunLandYacht]

The minivan is your toad?

The only way I see to wire the single panel into a solar charge control that will already have other panels wired into it is to make all the panels parallel. Put an SAE connector on the side of the motorhome and plug the single panel into that. From the SAE connector, the wire would go into a combiner box and from there into the solar charge controller.

I'm not sure the single panel is worth the hassle, but that's a novel way to add a panel.

Toad attached

Thanks HRTKD, we agree, I thought I would either run the input from the ground deployed panel back up to the combiner box or do a second SCC; which remains to be seen.

This past summer I (with my better half) spent two weeks in a beautiful campground along the Blue Ridge Parkway and enjoyed several nights BSing with some wonderful acquaintances around campfires. Two of them had some sort of solar setups. During this time was when I became interested in a solar system. No one ever said a word but I was the neighbor running the !?#.. generator (only during designated hours). What is the point of being surrounded by beautiful nature and forced to listen to someone's !?#.. generator?

One of the people with solar was directly across from me. His rv site had some shading, he had panels on the roof (don’t have details) but he said the three panels he had on the ground, in the sun were the ones saving him; they just adapted their need to available power from them. Makes sense to me.

Stay Safe, Mike​

 

[HRTKD]

I considered going whole hog and ditching my on-board 5500w generator. I would use the freed up space and weight for an inverter and more battery. For now, I run the generator when I need to run the microwave and the air conditioning.

The generator came in handy a couple weeks ago when I was camping at -10° F. Mainly to run a space heater and the tank heaters.

 

[Hedges]

So you burned 15 kWh of fuel to generate 5 kWh of electricity to heat something?

 

[HRTKD]

So you burned 15 kWh of fuel to generate 5 kWh of electricity to heat something?

Absolutely. The frozen water lines needed more heat than the furnace could provide.