Solar Power Efficacy?

[meaningful_meanderings]

How effective are solar electrical systems in RVs? Presume they work best with a correctly sized generator for back up. Are they worth it or should I save the weight for more propane to power the generator? I presume the batteries can also be charged from the tow vehicle while driving...? Does the electrical management system typically tie in with the generator to recharge storage batteries as needed when sufficient sun light is not available?

Thanks

 

[LarsMac]

I have met a number of people who are very pleased with their systems.
The solar can charge you batteries all day while you're driving, too.

 

[Isaac-1]

This really depend on how you camp, the great thing about solar is it is always charging when the sun is out, and it is silent. I have 400 watts of solar on my coach now (installed by the previous owner in 2015), plan to increase that to around 600-700 watts (space limited). 400 watts is about break even for me if I am in mostly sunny weather to provide power for LED interior lights, TV, laptop computer, phone charging, cell hotspot, roof fans / furnace blower, as well as limited higher power draw using the inverter for things like operating the microwave, or even limited cooking in the air fryer.

p.s. what solar will not do unless you have a very extensive, and expensive setup is run air conditioning. In theory my battery / solar setup could run my air conditioner, batteries for perhaps 3-4 hours per day, but with 400 watts worth of solar panels I only get about enough power to run air conditioner 1-2 hours per day.

 

[meaningful_meanderings]

Yea, I was tinkering with the idea of off grid some years ago (just the idea...) and realized it is a life style change. Figured that would have some impact on RVs solar too. Too, I keep thinking about the roof size paradox; more panels need more roof but more roof means bigger RV with usually means more stuff that uses electricity. I can see it potentially stretching the fuel supply for boondocking but requires stuff to be dual fuel.

Presume that with a decent PV (solar) system, on shore power the batteries function like a UPS?

 

[Isaac-1]

Usually not, but it really depends on the setup

 

[John From Detroit]

The question is rather complex. Depends on where and when you are. how many panels. What panels (some are better than others) and what Charge controller you have

In theory it's possible to not need a Generator at all but I'd not wish to test that theory till I tested it by having it and not using it save for one hour a month.

 

[Isaac-1]

When it comes down to it, any solar beats no solar, but at the same time more solar is almost always better. It is also about managing expectations

 

[Kirk]

I presume the batteries can also be charged from the tow vehicle while driving...

All modern RVs come with the capability to charge the battery from the chassis alternator.

How effective are solar electrical systems in RVs?

The only valid answer to this question is, maybe. The effect for solar depends on so many different factors that none of us can say what your experience will be. If you wish to learn about solar and so be able to figure out what you may want or need, I suggest you spend some time on the website of Chad Heiser Electric because Chad is a fulltimer who learned about solar mostly be reading and try things and now makes a business of RV solar systems. Because Chad has far more customers available than he is able or willing to serve, he has posted a great deal of excellent information on his site and he will gladly give advice to those wishing to do things themselves or to know what they need, absolutely free. Chad knows more about solar on RVs than anyone I have ever known.

 

[Mark_K5LXP]

Something I tell anyone that asks me about solar is to answer the question, "what problem are you trying to solve?" For some it's to run stuff without listening to a generator, or having to maintain one as much. Others it's the idea of being autonomous, not having to plug in or run a genset. This isn't easy, or free so you have to decide what the cost/benefit is for your goals. There's no payback, or return so whatever you put into it is solely for whatever utility you're looking for. Planning for clouds and reserve is another factor to add to the mix.

Mark B.
Albuquerque, NM

 

[LMHS]

To start with...
You run off a battery bank system, not a solar system.

Solar is just one way to recharge your battery bank system.

HandyBob's Blog

Making off grid RV electrical systems work

handybobsolar.wordpress.com

 

[solarman]

How effective are solar electrical systems in RVs? Presume they work best with a correctly sized generator for back up. Are they worth it or should I save the weight for more propane to power the generator? I presume the batteries can also be charged from the tow vehicle while driving...? Does the electrical management system typically tie in with the generator to recharge storage batteries as needed when sufficient sun light is not available?

Thanks

If designed correctly, then 100% effective.. solar is designed to meet a goal, that is, a specific known power consumption over a 24 hour period with battery capacity to allow for 5 days autonomy.

so that's the ideal, in practice, DIY RV installs rarely meet this goal.
generator size only needs to meet peak demand unless you have a system that acts as a UPS system.

One of the limiting aspects of an RV is roof real estate, it is often not possible to install sufficient PV to satisfy demand, hence many diy installs give solar a bad 'wrap' mainly due to poor design and over expectations.

having said that, there are ways to increase apparent PV area with stacking and sliding systems such as pictured here. This is a set on my daughters RV, there is a total of 1400 Watts on a 22ft roof. we could have maxed it out at 2400 Watts, but there was no need as this suits their requirements.
the system is designed to power the A/C overnight and has a battery capacity of 16,800 W/hrs

the system is all Victron and is designed as a UPS with generator backup.
the main inverter/ats/charger is a Victron multiplus 2 unit @3000VA

 

[Utclmjmpr]

I also have 400 watts on the roof,( installed be me 15 years ago) What I like is the ability to use a residential refer and run the coach heater all night,, and still awake in the morning with 12.3 levels in the battery bank ( 4- 6 volt deep dischargeable system ) This in my experience,,allows me to run the generator much less than I did before the install.. It has paid for itself many times over in fuel savings..>>>Dan ( I have roof windows in my garage roof and rarely have to charge the battery bank while stored.)..>>>Dan

 

[UTTransplant]

Our maximum efficiency for flat mounted panels on a sunny day ranges from 40% to 90%. The variation is winter vs. summer. Low sun angle means less efficiency, and you have to consider the shorter days making it worse to. In summer the sun is so much higher, and the days are longer. We can go days without the generator in the summer, but we need to run it daily for a short while in the winter. Since the propane furnace is a heavy hitter due to the fan, the draw is higher in the winter too.

 

[HueyPilotVN]

I have 1,600 watts on a 28 foot Class C, eight 200 watt panels, and 1,500 AH of Lithium batteries.

I have not yet had a chance to do a detailed test of the performance of the system under summer conditions.

 

[meaningful_meanderings]

If designed correctly, then 100% effective.. solar is designed to meet a goal, that is, a specific known power consumption over a 24 hour period with battery capacity to allow for 5 days autonomy.

so that's the ideal, in practice, DIY RV installs rarely meet this goal.
generator size only needs to meet peak demand unless you have a system that acts as a UPS system.

One of the limiting aspects of an RV is roof real estate, it is often not possible to install sufficient PV to satisfy demand, hence many diy installs give solar a bad 'wrap' mainly due to poor design and over expectations.

having said that, there are ways to increase apparent PV area with stacking and sliding systems such as pictured here. This is a set on my daughters RV, there is a total of 1400 Watts on a 22ft roof. we could have maxed it out at 2400 Watts, but there was no need as this suits their requirements.
the system is designed to power the A/C overnight and has a battery capacity of 16,800 W/hrs

the system is all Victron and is designed as a UPS with generator backup.
the main inverter/ats/charger is a Victron multiplus 2 unit @3000VA

Does the generator interact with the power management system or do you have to start manually as required?

I was unaware of the telescoping/nesting panels, that changes things a bit.

 

[Isaac-1]

There are auto start generator controllers that will automatically start the generator under certain conditions, such as auto when battery drops to a certain voltage, or auto start when thermostat calls for air conditioning, etc. Though they are rarely standard equipment.

 

[solarman]

Does the generator interact with the power management system or do you have to start manually as required?

I was unaware of the telescoping/nesting panels, that changes things a bit.

The Victron multiplus becomes the power management system in this case.

The victron system has the capability to control input and output power from shore/generator and battery concurrently. The battery SOC is monitored and a relay activated to start the generator when needed.

the victron unit also provides an assist to shore/generator input and adds energy from the batteries when heavy loads are applied. when shore/generator input exceeds load, it charges the battery with the surplus energy. It's a real nice system and changeover from shore/battery/invert is seamless..

I need to post an article on the multiplus unit..

the telescoping panel assembly is my own design.

 

[meaningful_meanderings]

The Victron multiplus becomes the power management system in this case.

The victron system has the capability to control input and output power from shore/generator and battery concurrently. The battery SOC is monitored and a relay activated to start the generator when needed.

the victron unit also provides an assist to shore/generator input and adds energy from the batteries when heavy loads are applied. when shore/generator input exceeds load, it charges the battery with the surplus energy. It's a real nice system and changeover from shore/battery/invert is seamless..

I need to post an article on the multiplus unit..

the telescoping panel assembly is my own design.

Where did you find drawer slides that long? You using LFP batteries or the regular Li? Definitely post the article.

 

[solarman]

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