Realistic use of solar for solar NEWB

[RamblingMan22]

380 watts of solar panels. 4 pack of 6V batteries. 3000W inverter.

This is the solar setup on the 26 ft bumper pull toy hauler that I just purchased. Realistically, how can I expect that setup to work for me? My main uses would be as follows:
-I’ll use the trailer a lot at construction sites and campgrounds where shore power is available.
-About once/year I take a longer road trip for a week or more. On these trips it would be nice to have some power available for sleeping in rest stops, or more remote and primitive camp sites— just for 1-2 nights at a time between shore power charges. I’m not needing every appliance on when I do this. Maybe some lights, the fridge, a cell phone charger, and enough juice to run the AC for an hour or two in the evening?!?! (This is my ultimate goal for building a solar system… even if I have to add to my current setup)

And… now the dumb questions (that I will also be asking the dealer and asking for instructions)… what do I have to do to run a solar system? Are they mostly plug and play? Or will I have to turn charging on and off? How do I monitor battery usage, because it’s important to stop draining the batteries past a certain point, right?

Sorry… I’m a newb.

 

[Kirk]

RV Solar Simplified! Simple RV Solar Setup.​

Watching this should help. For specific instructions we would need to know exactly what your RV has.

 

[PJ Stough]

To my way of thinking, with four 6 volt batteries, hopefully they are deep cycle, you should have about 200-225 "useable" amp hours. With that I would want 600-700 watts of solar power. I would use a 45 amp MPPT controller, and a 2000 watt pure sine wave inverter.
You wont be able draw enough amps from the batteries fast enough to make a 3000 watt inverter practical, as at close to max amp draw, the battery voltage with drop below inverter low voltage cutoff.
The 600-700 watts of solar will come close to maxing out the 45 amp controller, and give you about 200 amp hours of solar input during the day, unless of course it is cloudy.

 

[Mark_K5LXP]

Recommendations toward my solar plan

Are they mostly plug and play?

Depends on your definition of "mostly".

Mark B.
Albuquerque, NM

 

[Ex-Calif]

380 watts of solar panels. 4 pack of 6V batteries. 3000W inverter.



Sorry… I’m a newb.

Don't be sorry about being a newb. We've all started somewhere. Welcome aboard.

The first practical use of solar is to be able to make extended trips off grid without plugging in, affording the use of the 12V systems on board.

Advanced solar installs with "high power" and "high collection" rates coupled with an inverter may allow use of A/C systems.

Your batteries are most surely wired to produce 12V so you probably have about 400 a/h. It is useful to understand power which is measured in Watts, like a hair dryer.

Volts X amps = Watts so 400 X 12 = 4800 Watts or technically Watt/hrs - About half to 2/3rd of that is available before the voltage drops too low to b useful so you probably have 3,000 watt hours to play with.

So a 1500W hair dryer would last about 2 hours. With your 3,000W inverter you can run all kinds of appliances for a short period of time including coffee pots, blenders etc. etc.

Once the juice is used it needs to be replenished. You are sure to have a plug in battery charger/Power supply. 40 amps is a typical number.

40 amps X 12V = 480W - So that's available to run the house and charge the batteries.

In regard to the 380W of solar it is limited to some collection limitations - like only during daylight sun and season will affect how directly the sun hits the panels. A general formula is 80% collection efficiency X 6 hours of collection.

So 380 X 6 X .8 = 1824W. What this means is that if you are using the hair dryer for 2 hours a day (3,000W) you will run a deficit and over a few days the batteries will be dead unless you plug into shore power.

From your described usage you will be plugged in most of the time. Having solar for you is nice but probably not necessary.

A typical solar install is wired into the charging system seamlessly. There may be an isolation breaker somewhere but for practical purposes it should be seamless to you and do its own thing automatically.

 

[Mark_K5LXP]

The thread I linked is a very similar scenario so that can provide some background without repeating here.

As far as solar goes, a key consideration is that the sun don't always shine. If you're in Arizona or New Mexico it shines "more" but in my travels, wherever I've camped has trees or geography that can impact the duration or intensity of sunlight. Clouds are pretty much game over, you don't get zero output it's a small fraction of their capacity. So if you're out in the desert in the middle of summer, they work great, you get all you paid for. But wait - if you're out in the desert in the middle of summer you're also going to be baking inside that RV, so most or all of the energy you collect will go towards A/C. I would much rather camp in the shade than bake in the sun to keep the panels happy. OK, so you get portable panels so they bake in the sun while you're in the shade. But now you every time you camp you have to haul out the panels, find a spot, run wires and attend to them. Then figure out a way to secure them so they don't wander away, or you have to haul them in and out every time you leave camp. Lather, rinse, repeat every time you want solar. Once in a while it's OK, I have a portable panel in mine I'll lay out sometimes when I want to use some of my radio gear away from the RV but the long and short of it is I treat solar (I have some rooftop too) strictly as supplemental. All free Ah are good Ah, but I don't even bother to keep track and I just plan on running the generator when I want A/C or the batteries need to be topped off. A few cloudy days, or a shady camping spot and it doesn't matter how much solar or how big a battery you have, you're running the generator or sitting in the dark. Just making the point that you *can* make solar work if that's the primary goal but it won't be simple or cheap. Just decide how important solar is to you, how much genset time is acceptable and design accordingly.

Mark B.
Albuquerque, NM

 

[Gary RV_Wizard]

Using that solar system is is simple - it's just a battery charger that operates when and if there is sufficient sun to produce useful power. When feasible, it automatically adds amp-hours to the batteries, even when on shore power. When you lack shore power, your equipment, lights or whatever, runs off the batteries. The 12vdc stuff runs direct and the 120vac stuff runs thru the inverter, which in turn draws from the batteries. So you don't have to do anything special to make it work - it's pretty much magic.

The more complicated discussion is how much charging do you get and how much power you can draw from the batteries before they run dry (go "dead"). The sunshine is a finite amount per day, depending on where you are and time of year. The inverter is a huge draw because boosting the voltage by a factor of 10 to get 120v requires that the amp draw from the batteries be 10x the inverter output amperage. For that a/c unit, it's huge number. A typical RV a/c unit draws 11-14 amps (depends on age & btu rating), so 10x means you are pulling 110-140 amps from the batteries (plus the conversion power loss, roughly an additional 10%). Even 4x 6v batteries (about 420 amp-hours) doesn't last long at that rate. Others have addressed the monitoring question already.

 

[NMJEEP]

Depends on how you use it. When we are not on shore power we do not use AC power (inverter). Our Solar can maintain our batteries without any issues as long as we are just using DC. In our case that is lights, refrig, heater if needed, water pump. The refrig is on propane but needs DC for the circuit board. Heater is propane and DC for blower motor. Never had the batteries go below 2/3 charge and by mid afternoon they are back at 100%. Helps to have been a tent camper before owning an RV.