Need expert review on my First System Design for my RV

mjsandiego2003

New Member
Hi all,

First post here, and I'm hoping you all can give me solid advice. I am trying to maximize the solar charging and battery storage on my 2020 Thor Magnitude RV. I have no background in PV system design, but I do my research and hope my first attempt isn't too full of issues. I'm a relatively experienced engineer, but not with PV, or any significant electrical systems.

My coach is somewhat unique in that it has a residential refrigerator inside, and a mini-fridge outside, both of which are electric only. With the two 6V batteries I currently have, I am not able to even make it through the night while boondocking in the desert. And we boondock... alot. Like 10-16 weeks a year. I do not need to run AC, or go bigger than the current 2k inverter inverter I have (It covers the fridges, TV, fans and a few 110 outlets in the coach), really just trying to keep the batteries charged without running the generator 8-10 hours a day while boondocking. Oh, and without completely braking the bank.

My main constraint s I really do not want to put more holes in my roof. and my wife Reeeeaaaaaalllly doesn't want them either, and as they say, Happy wife, Happy Life. My second constraint is space, I cannot afford to give up a storage bay for solar, and the electrical system is literally right under the dinette (Plus they are insulated)

Fortunately my coach is "pre-wired" from the factory for solar, only problem is its with 10awg wire. So my thought are...crank up the voltage. I can physically fit at least 8 Renogy 175W Flexible panels on my TPO roof. My initial calculations (compensating for temperatures, and giving 25% margin) for those panels with 4 panels in series, and 2 parallel series has 1400W, Voc @ ~104.43V and ~23.75Amax. Assuming those numbers are close, I have some questions are my questions:
  1. Is that safe/appropriate to be running those numbers through ~25ft of 10awg wire?
    1. If the problem is too high a voltage, I can knock the series down to 3 in series, I get 1050W and Voc 78.32 which is better than nothing.
    2. If the problem is current, what's the max current I should run?
  2. I plan on using flexible panels, glued to the roof (maybe using corrugated plastic underneath for some insulation). I know rigid panels that tilt are ideal, but remember the holes in the roof issue. So I know I am going to face some inefficiencies due to angle, and heat. Is it ok to use a 60A Renogy Rover MPPT and just cap the output power at 800W? None ever gets listed wattage in rea-lworld output, I figure If I can get a solid 800W I should be fine. Price is attractive as well as size, which is the bigger issue. Again, I am not looking for the most efficient system, but I do want it to be reliable.
  3. What else am I missing? Below is the current plan. I'm looking to start purchasing parts, and have a parts list, but the main components that may not be recognizable are:
    1. Renogy 30ADC-DC converter (I like this not only for alternator charging, but picking up a few "briefcase" type panels if I have need more charging)
    2. Renogy Rover 60A MPPT (Inexpensive, only reason Its on my list, if this is a bad idea, I'll upgrade to a higher amperage)
    3. Victron Lynx (I imagine i could just use a busbar, but it seems like all the cool systems have this)
    4. WFCO WF-9855-LiS (This converter is plug-and-play in my coach)
    5. Battlborne GC2 (no brand loyalty here, I am also interested in the SOK. I originally thought about these because they will fit in the stock battery tray, but I decided against putting them there due to cold exposure.)
Thanks for all the feedback, good or bad!

System for Thor Magnitude.png
 

HRTKD

Boondocker
I understand you don't want to put any holes in your roof, but rigid panels are more reliable and with larger panels you can put fewer of them on the roof. The 10 awg wire should be good enough as long as the volts are high and the amps are low and the distance isn't too long. Use this wire gauge calculator to know for sure:


A two-pole circuit breaker between the solar charge controller and the solar panels is recommended. This is a handy way to turn off input of the solar panels should you need to work on the system with the battery disconnected. A breaker after the solar charge controller is also needed. What you have in your design MIGHT be a breaker/fuse, but I can't tell what you have there. For the portable solar, skip the inline fuse. Just put the same type of breaker there that you use for the roof panels.

I'm not a fan of the Renogy DC/MPPT units. They have a PVmax of 25 volts. That's crap. Get a real MPPT and DC-DC device designed to handle your inputs.
 

mjsandiego2003

New Member
I understand you don't want to put any holes in your roof, but rigid panels are more reliable and with larger panels you can put fewer of them on the roof. The 10 awg wire should be good enough as long as the volts are high and the amps are low and the distance isn't too long. Use this wire gauge calculator to know for sure:


A two-pole circuit breaker between the solar charge controller and the solar panels is recommended. This is a handy way to turn off input of the solar panels should you need to work on the system with the battery disconnected. A breaker after the solar charge controller is also needed. What you have in your design MIGHT be a breaker/fuse, but I can't tell what you have there. For the portable solar, skip the inline fuse. Just put the same type of breaker there that you use for the roof panels.

I'm not a fan of the Renogy DC/MPPT units. They have a PVmax of 25 volts. That's crap. Get a real MPPT and DC-DC device designed to handle your inputs.
Great advice, thanks for responding. I meant to put in the circuit breaker after the panels, but somehow missed it. Good catch.
 

mjsandiego2003

New Member
Here is the revised schematic. I've also upgraded to the Victron 150/100 MPPT. The more I've thought about it, I don't think trying to save a couple hundred bucks is worth limiting the solar potential, and it's physically smaller, which is a benefit for me.

Also, regarding the rigid panels, I agree with your logic, and appreciate the advice. Unfortunately for my application, due to the large number of OEM components on the roof, there are not many good spaces for larger/longer 200 or 320 Watt panels, and using them means less panels which leads to only 1200W. I could use the Rigid 160 (3S3P) or 100, but then it's even more panels, which seems like chasing my tail to eek out a few more Watts. The primary advantage I see to the Rigid for me, is the ability to tilt,. This is much more in my wheel house, and I'm might try to implement a semi-permanent mounting system using no screws, which allows the panels to tilt. More details on that once I figure out what the electrical system looks like.

Any other thoughts, from you or others???
 

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HRTKD

Boondocker
The way you have your individual batteries connected is old school. When using LiFePO4 batteries in parallel, the usual recommendation is to connect each battery to the common bus bar or to a common battery bus bar which is then connected to the system's common bus bar.

This method gives equal access to all batteries, at the same resistance. The batteries could probably get by with 2/0 cable to the common bus bars.
 

Nakinto

Solar Enthusiast
If cost wasn't an issue, I would say build a frame around the rig. Attach it to the underframe of the vehicle and run just bars across the roof, only need to bolt/glue it down in maybe 4 spots on the roof and the panels will be above all the OEM components and most of the weight won't be sitting on the roof but on the frame of the vehicle. But you want something that doesn't brake the bank.

Amperage is fine, 10 AWG is good up to around 35 amps, and MOST 10 AWG wire you will find is 600v rating on the insulation so no problem there. The only issue would be voltage and the charge controller, but that CC looks like it will handle 150v so 104 would be fine.

The only thing I don't see is the battery capacity. I would highly recommend a good 6 KWH useable minimum possibly 10 as fridges are hungry things, I know my fridge (regular AC only) uses a good 3-4 KWH a night, although, it is older and probably failing, used to only use 4 KWH a day.
 

mjsandiego2003

New Member
The only thing I don't see is the battery capacity. I would highly recommend a good 6 KWH useable minimum possibly 10 as fridges are hungry things, I know my fridge (regular AC only) uses a good 3-4 KWH a night, although, it is older and probably failing, used to only use 4 KWH a day.
I get your point, and have considered more batteries. The 4 x GC2 was due to the battery compartment’s available space, but I’ve already decided on a new location. I’ve yet to measure the bench seat space and determine the if I can do better, but it is likely that I can get 2 more in there.
 

Nakinto

Solar Enthusiast
I get your point, and have considered more batteries. The 4 x GC2 was due to the battery compartment’s available space, but I’ve already decided on a new location. I’ve yet to measure the bench seat space and determine the if I can do better, but it is likely that I can get 2 more in there.
GC2 is a 450 AH battery, 6v right? So 4 would be 12v, 900AH or 24v 450 AH, and about 11KWH total @ 20% 2 KWH useable under best practices, but these are deep cycle golf cart batteries so they are specifically designed to be able to take more of a beating and you can probably eak out double that useable without TO much degradation, but as with all LA batteries, the deeper they are cycled the shorter the lifespan.

Limited space is a PITA, I found that my best spot was underneath the bed for MY system, just enough room to fit about 220 AH at 48v A 4s2p configuration. Now, your system is going to be completely different, so I don't want anyone to take it that I am recommending this as a solution.
 

mjsandiego2003

New Member
GC2 is a 450 AH battery, 6v right? So 4 would be 12v, 900AH or 24v 450 AH, and about 11KWH total @ 20% 2 KWH useable under best practices, but these are deep cycle golf cart batteries so they are specifically designed to be able to take more of a beating and you can probably eak out double that useable without TO much degradation, but as with all LA batteries, the deeper they are cycled the shorter the lifespan.

Limited space is a PITA, I found that my best spot was underneath the bed for MY system, just enough room to fit about 220 AH at 48v A 4s2p configuration. Now, your system is going to be completely different, so I don't want anyone to take it that I am recommending this as a solution.
I was specifically referring to the Battleborne LiFePO4 GC2, which have the golf cart battery form factor. The are 12V and 100Ah each, so ~1200Wh x 4 in the above schematic = ~4800Wh. 6 would bring it up to 7200WH, assuming full discharge.

https://battlebornbatteries.com/product/100ah-12v-gc2-lifepo4-deep-cycle-battery/
 

DJSizzleC

New Member
I understand you don't want to put any holes in your roof, but rigid panels are more reliable and with larger panels you can put fewer of them on the roof. The 10 awg wire should be good enough as long as the volts are high and the amps are low and the distance isn't too long. Use this wire gauge calculator to know for sure:


A two-pole circuit breaker between the solar charge controller and the solar panels is recommended. This is a handy way to turn off input of the solar panels should you need to work on the system with the battery disconnected. A breaker after the solar charge controller is also needed. What you have in your design MIGHT be a breaker/fuse, but I can't tell what you have there. For the portable solar, skip the inline fuse. Just put the same type of breaker there that you use for the roof panels.

I'm not a fan of the Renogy DC/MPPT units. They have a PVmax of 25 volts. That's crap. Get a real MPPT and DC-DC device designed to handle your inputs.
Hi just a quick one on the Wire Size Calculator. It doesn't say what the unit of measure is for Length.

Is it m (metre), yds (yards), ft (feet) or ins (inches) ?


Thanks
 

HRTKD

Boondocker
Hi just a quick one on the Wire Size Calculator. It doesn't say what the unit of measure is for Length.

Is it m (metre), yds (yards), ft (feet) or ins (inches) ?


Thanks

You're right, it doesn't specify the unit of measure. I'm fairly sure it's feet. The site is based in the U.S., so feet is the norm.
 

synergicity

Solar Enthusiast
I get your point, and have considered more batteries. The 4 x GC2 was due to the battery compartment’s available space, but I’ve already decided on a new location. I’ve yet to measure the bench seat space and determine the if I can do better, but it is likely that I can get 2 more in there.
I am a little confused that you are willing to spend four grand on batteries and then are going to cheapen out on the more crucial items and go with Renogy? Your rig is probably close to $200K and super nice, so don't under buy on the charging system components. I would build batteries (although I understand why you might not) and then get the best other parts I could afford. Victron plays very well with other Victron gear and if you like consistent look and feel to the gear and interfaces, that is a neat way to go. Influencers seem to dig the Redarc equipment which is also very integrated with itself. I tried to maximize functionality for my budget and ended with Epever for MPPT, Progressive Dynamics for the shore charger, and Sterling for the DC/DC.

Also I am confused on why there is an AC only frig? There are so many good options that don't require 120V AC. If you do want to boondock 10-16 weeks a year, it is maybe not the optimal choice if you also don't want to be running a generator all the time. I assume you have done all the math on your loads and what that means and have planned for a week of cloudy weather. I see now that you have a big generator, so I guess that you do plan to use that when the sun isn't shining. I am assuming that is a 6000W generator and not a 600W. I hope you aren't parked near me.
 

mjsandiego2003

New Member
I am a little confused that you are willing to spend four grand on batteries and then are going to cheapen out on the more crucial items and go with Renogy? Your rig is probably close to $200K and super nice, so don't under buy on the charging system components. I would build batteries (although I understand why you might not) and then get the best other parts I could afford. Victron plays very well with other Victron gear and if you like consistent look and feel to the gear and interfaces, that is a neat way to go. Influencers seem to dig the Redarc equipment which is also very integrated with itself. I tried to maximize functionality for my budget and ended with Epever for MPPT, Progressive Dynamics for the shore charger, and Sterling for the DC/DC.

Also I am confused on why there is an AC only frig? There are so many good options that don't require 120V AC. If you do want to boondock 10-16 weeks a year, it is maybe not the optimal choice if you also don't want to be running a generator all the time. I assume you have done all the math on your loads and what that means and have planned for a week of cloudy weather. I see now that you have a big generator, so I guess that you do plan to use that when the sun isn't shining. I am assuming that is a 6000W generator and not a 600W. I hope you aren't parked near
Thanks for the feedback. As I mentioned, this is my first system, and I was unaware that Renogy is “cheapening out” the system. I will probably go with the Victron setup as shown in my second iteration. As to the residential fridge... that’s what the coach came with, and the 6kw generator is diesel, and surprisingly quiet. Fortunately for me 90% of the boondocking we do is in the deserts of Southern California, so days of sun are not much of an issue
 

The_Breeze

The Breeze
I get your point, and have considered more batteries. The 4 x GC2 was due to the battery compartment’s available space, but I’ve already decided on a new location. I’ve yet to measure the bench seat space and determine the if I can do better, but it is likely that I can get 2 more in there.
Your diagram seems to show 4 BB LifePO4 batteries, not GC2 golf cart batts?

If you do go Lith, remember to change out your BIM/BIRD for a LBIM.
 

The_Breeze

The Breeze
The way you have your individual batteries connected is old school. When using LiFePO4 batteries in parallel, the usual recommendation is to connect each battery to the common bus bar or to a common battery bus bar which is then connected to the system's common bus bar.

This method gives equal access to all batteries, at the same resistance. The batteries could probably get by with 2/0 cable to the common bus bars.
Thank you for this I was unaware and would have went old school. You mention resistance. Won't that occur due to different cable lengths to reach the bus bar? Maybe you could improve on this setup? It's locate under the steps in my Rig. I have to reach the breaker on the right.
1622141058928.png
 
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The_Breeze

The Breeze
Just came across that pic via the blueprints section but the thread itself seems to be missing info. Revisions and comments are there, but nothing else?
 

The_Breeze

The Breeze
Gold mine! THANK YOU! I have 4 BB 100s 12V. Will assume the rule still applies.

I'm building the next battery bank myself.
 
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