RV Solar Concept

[dougybug]

Hello Everyone. My name is Doug. My wife and I have purchased our first RV for our retirement dream. We hope to do a great deal of boondocking, so I wanted to add a solar package to our RV. I am new to the world of solar power, but do have some electrical experience. I am trying to learn as much as I can so I do not make any costly mistakes.

I have sketched out a concept for a system and wanted to get others inputs on my idea. The sketch really only shows flow, disregarding DC polarity and fusing. I wanted to add the package with as little interference to the RV's original electrical system as possible. That is why I am not tapped into the RV's 12 VDC system. I may upgrade the onboard 12 VDC battery to a 206 Ah LiFePo battery, but that is probably the only modification I want to do to the original system.

Your thoughts, concerns and inputs will be greatly appreciated. Thank you.

Doug

 

[corn18]

Is your RV a 50A or 30A system?

 

[dougybug]

30A system. Our RV is being stored at the dealership till spring (having them hold it, allows us to have the full warranty once we drive it off the lot), so I still need to size everything, but I hope this design fits or I will have to downsize accordingly.

 

[Browneye]

Lots of batteries....you're going to run AC off them?
4000w - do you also have a 4kw generator?

 

[dougybug]

Yes, planning on running AC if needed (short term) using soft start circuit.
Yes, the RV has a 4000 watt generator.

 

[corn18]

30A system. Our RV is being stored at the dealership till spring (having them hold it, allows us to have the full warranty once we drive it off the lot), so I still need to size everything, but I hope this design fits or I will have to downsize accordingly.

Ok, so we can simplify your design a lot. You want to get a 24V/4000W inverter+charger with a 30A ATS built in. That will eliminate the second transfer switch and the converter. Just feed the output from your existing ATS into the inverter/charger. This also eliminates any chance of inverting and charging at the same time.

 

[12VoltInstalls]

So the ‘converter’ on the bottom is probably actually an inverter?

You do not include details of disabling the oem converter when the 24DC>120VAC inverter is running.

Opinion: I would not use the solar for the air conditioning myself. Leave that to the generator. Although you have enough batteries to do that for quite a while.
I say this for two reasons:
1) with only three panels shown of unknown size but guessing 250W? I’m not confident you’d have enough solar watts to run, recharge and do other things on the power incoming. You might? But the unknown loads make it a guess right now.
2) the 4000W inverter is borderline big for 24V.

Or a third thought: a 3000W all-in-one seems totally clean and simple: and it may even do the air conditioner, maybe handle shorepower switching, and eliminate your need for the likely inefficient oem ‘converter’ completely.
Integration of the oem electrical with an AIO would make using everything invisible. You won’t know if you’re on shorepower or solar in use. If the air conditioning draw is light enough plugging in to shorepower might even be too much inconvenience. The only other thing to solve is your 12V systems. Other than brakes and leveling everything can be easily changed to the new 24V provided the wiring is rated for it- leaving the oem battery to leveling and emergency brake tasks.
Running the oem converter for 12V lights and the water pump will use a lot of battery power inefficiently.

 

[dougybug]

Thanks corn18. I will look into size and pricing of an inverter/charger w/ats. Sadly I may have to downsize depending on packaging since we are going into a smaller size class C (Jayco Redhawk 24B).

 

[deeuubee]

Is this for the Redhawk 24 in you profile? If so, where would you possibly put all those batteries and equipment.
You would need a really high amperage charger and panels to cycle and charge that bank in one day.
It just seems like a super large expense just to power a microwave. Care to share you load intent?
If you plan on using the microwave and A/C for short periods of time, the generator is you friend.

 

[dougybug]

I don't think I can justify the savings over gasoline and the generator, but in the future maybe. Their may even be a concern for availability. There have been times our local small town gas station has been without gas in the last few months. After installation, I wil look at it as a sunk cost. This is more to supplement gasoline and the generator, rather than to replace it. I am not sure how I will package it, thinking maybe under the "U" shaped dinette and vent both ends. Still need to work out thoset details. My load intent is to be able to carry a 30A demand as if on generator or shore power. I also want to be able to supplement charging of the battery bank when on generator or shore power.

 

[Browneye]

Certainly ambitious!
We're in a 32' class-A with 600w of solar, 600w inverter, a 230A lifepo pack, and 4kw onan.
The coach is 17 years old this year, we've traveled nearly fifty thousand miles in it, mostly dry camping.

One of the threads I started on panel mounting, has some of the battery pack stuff too:

Old RV - New PV's With Strut-Channel Mounting

I'm new here, starting a new thread on my 430W installation, so I can ask questions when they come up. This forum has been a wealth of information. I have also been scouring the 'net for, and learning about, LiFePo4 batteries as well. I'm not sure where I first saw strut channel mounting for...

diysolarforum.com

 

[dougybug]

So the ‘converter’ on the bottom is probably actually an inverter?

You do not include details of disabling the oem converter when the 24DC>120VAC inverter is running.

Opinion: I would not use the solar for the air conditioning myself. Leave that to the generator. Although you have enough batteries to do that for quite a while.
I say this for two reasons:
1) with only three panels shown of unknown size but guessing 250W? I’m not confident you’d have enough solar watts to run, recharge and do other things on the power incoming. You might? But the unknown loads make it a guess right now.
2) the 4000W inverter is borderline big for 24V.

Or a third thought: a 3000W all-in-one seems totally clean and simple: and it may even do the air conditioner, maybe handle shorepower switching, and eliminate your need for the likely inefficient oem ‘converter’ completely.
Integration of the oem electrical with an AIO would make using everything invisible. You won’t know if you’re on shorepower or solar in use. If the air conditioning draw is light enough plugging in to shorepower might even be too much inconvenience. The only other thing to solve is your 12V systems. Other than brakes and leveling everything can be easily changed to the new 24V provided the wiring is rated for it- leaving the oem battery to leveling and emergency brake tasks.
Running the oem converter for 12V lights and the water pump will use a lot of battery power inefficiently.

I labeled that incorrectly, I will be using it as a charger for the 24 VDC battery bank which is isolated from OEM 12 VDC system. My only intent for the solar package is to feed the 4000 watt inverter which will feed the input of the 110 VAC, 30 A OEM system in place of the generator or shore power (inserted after generator transfer switch with an additional transfer switch). It may seem like overkill, but I want the system to be able to handle a 30 A load as would the generator or shore power.

 

[corn18]

I labeled that incorrectly, I will be using it as a charger for the 24 VDC battery bank which is isolated from OEM 12 VDC system. My only intent for the solar package is to feed the 4000 watt inverter which will feed the input of the 110 VAC, 30 A OEM system in place of the generator or shore power (inserted after generator transfer switch with an additional transfer switch). It may seem like overkill, but I want the system to be able to handle a 30 A load as would the generator or shore power.

I think that is a great plan. If you use the all in one 24V inverter/charger, the system will operate seamlessly. Really simple install, as well. Just install the inverter/charger on the AC output from the existing ATS. You can probably just break the existing wire and plop the inverter/charger in the break. Then install the 24-12 DC-DC converter to feed the existing 12V system. Easy peasy.

 

[dougybug]

Certainly ambitious!
We're in a 32' class-A with 600w of solar, 600w inverter, a 230A lifepo pack, and 4kw onan.
The coach is 17 years old this year, we've traveled nearly fifty thousand miles in it, mostly dry camping.

One of the threads I started on panel mounting, has some of the battery pack stuff too:

Old RV - New PV's With Strut-Channel Mounting

I'm new here, starting a new thread on my 430W installation, so I can ask questions when they come up. This forum has been a wealth of information. I have also been scouring the 'net for, and learning about, LiFePo4 batteries as well. I'm not sure where I first saw strut channel mounting for...

diysolarforum.com

Very ambitious, but I am going all out. We are selling everything, banking what's left and hitting the road full time. I am afraid we will probably have that many miles on our rig in a couple of years. Thank you for all of your input. I may be crazy, but I figure I need to go big or go home.

 

[dougybug]

I think that is a great plan. If you use the all in one 24V inverter/charger, the system will operate seamlessly. Really simple install, as well. Just install the inverter/charger on the AC output from the existing ATS. You can probably just break the existing wire and plop the inverter/charger in the break. Then install the 24-12 DC-DC converter to feed the existing 12V system. Easy peasy.

Actually I had planned on letting the OEM converter running off the RV's VAC system charge the 12 VDC house battery. And the 24VDC/4000 watt inverter to run the RV's VAC system. I don't want to alter the OEM system except to add a third VAC input (generator, shore power, solar powered inverter). Thank you for the idea of an integrated inverter/charger/ATS. I will definitely see if I can find one that meets my need and price range.

 

[corn18]

Actually I had planned on letting the OEM converter running off the RV's VAC system charge the 12 VDC house battery. And the 24VDC/4000 watt inverter to run the RV's VAC system. I don't want to alter the OEM system except to add a third VAC input (generator, shore power, solar powered inverter). Thank you for the idea of an integrated inverter/charger/ATS. I will definitely see if I can find one that meets my need and price range.

That works, too. A little inefficient, but your DC loads won't be huge so not a big deal. I like your design.

 

[deeuubee]

Yes, planning on running AC if needed (short term) using soft start circuit.
Yes, the RV has a 4000 watt generator.

You are looking for opinions " so I do not make any costly mistakes."
So, I have to try to stop you from squirrel hunting with a cannon
It's your money, but let me make my case.

If you don't use your A/C, the concept works fine, but would work fine at 12V also at 1/2 the cost.
If you use the A/C for only 2 hrs a day, you would need 5 good hours of sun to replace just that with 600 watts of solar.
Assuming around 1500 watts a day of normal full time use (hair dryer, micro, toaster, coffee pot, etc) you might get a week with that large battery bank before you run out. You then have to run the generator for 6 hours to power a 100 amps charger to get it back up since your using all of the available solar just to replace the A/C usage.
Now matter how you look at it, you have to run the generator a good amount if you want to use the A/C regularly.
It seems like an expensive concept to save from running the generator a few more hours a week.
I'm not looking to discourage you, just trying to understand the concept. Good luck.

 

[dougybug]

Thanks deeuubee. You make some good points. Maybe I need to look more into the pluses of a generator. I am not sure of how the longevity of a generator stacks up against solar or what the mean time to failure for either are. I will definitely return to this post with whatever I do. But do know, I appreciate your input and anything can change as I am still in the planning stages.

 

[12VoltInstalls]

had planned on letting the OEM converter running off the RV's VAC system charge the 12 VDC house battery

A little inefficient, but your DC loads won't be huge so not a big deal.

The oem house ‘converter’ will likely use 10A for 5A of load.
One 100W panel and a pwm will probably maintain the house battery

I am not sure of how the longevity of a generator stacks up against solar or what the mean time to failure for either are.

the little hondas or their HF copy last a long, long time. But not as long as solar components at probably 20+ years will

 

[dougybug]

The oem house ‘converter’ will likely use 10A for 5A of load.
One 100W panel and a pwm will probably maintain the house battery

the little hondas or their HF copy last a long, long time. But not as long as solar components at probably 20+ years will

12VoltInstalls, thanks for your input. I am really glad I was able to bounce my concept off so many people. I must admit it has given me a lot to think about. I will updated you all when my plan (whatever it is then) comes to fruition. Thanks to everyone for helping me to make an educated decision.