Portable solar for limited current draw

[ohhell10339]

I want to be able to generate enough power to run my laptop and keep a couple of lights inside the RV lit.

1. Will a 100 watt portable solar array do it? Or will I need 200? (Let's assume that I'll usually have sunlight.)
2. What's the easiest way to use the DC output of the panel(s) to light the interior of the rig (and maybe run things like a fan and/or the water pump)? In a rig that doesn't have a generator, where would the interface be? (I assume it would be horribly inefficient to run the output through an inverter and then connect the inverter to the shore power plug.)
3. Likewise, what would be the mechanism I would use to charge the house batteries with the panels' output? Keeping in mind I want all this to be portable, so no permanent hard wiring.

[MrWizard]

yeah, that is constant problem here

the OP wants, what we all want, enough power to not worry about the battery
and we all know that in 99.9% of situations 100w is not enough

it can be help, extend the amount of power available during a weekend camping trip
it won't be enough for extended use, other means of recharging the battery and having power will be needed

he did not want to hear that, NONE of us ever do

[SoundGuy]

Almot wrote:
You don't get it, people - the question was about power from 100W solar, and we were told not to assume.

Yes, 100W will generate enough power to run laptop on some tasks.
No, 100W solar will not run couple of lights, and neither will 200W, because solar won't work during the time that people usually need lights 🙂

Round 4...

Yeah, EXCUSE US for "assuming", the only choice available when the OP refuses to provide complete information. :S

[Almot]

You don't get it, people - the question was about power from 100W solar, and we were told not to assume.

Yes, 100W will generate enough power to run laptop on some tasks.
No, 100W solar will not run couple of lights, and neither will 200W, because solar won't work during the time that people usually need lights 🙂

Round 4...

[SoundGuy]

steveh27 wrote:
My 2310 Dometic fridge on propane draws no electric. It is 20 years old.

SoundGuy wrote:
So yours is a manual light fridge ... but what has that got to do with the OP who as far as we know has a conventional DSI fridge? :h

steveh27 wrote:
Mine has the Piezo lgnitor to light the propane. While running on propane there is no draw on my battery. Works great for boondocking.

Agree, a manual light fridge with a piezoelectric ignitor is most suitable when dry camping as it requires no 12 vdc power to operate. If the OP would respond and clarify exactly what fridge he has that he seems to think will run on propane without any draw down on his trailer battery we could then determine whether this is true or not. If it's a DSI fridge then he's sadly mistaken - it won't run at all. 😞 Since his original question was about "how much" solar he needs this is an important question to answer.

[steveh27]

SoundGuy wrote:

steveh27 wrote:
My 2310 Dometic fridge on propane draws no electric. It is 20 years old.

So yours is a manual light fridge ... but what has that got to do with the OP who as far as we know has a conventional DSI fridge? :h

Mine has the Piezo lgnitor to light the propane. While running on propane there is no draw on my battery. Works great for boondocking.

[MrWizard]

Here
97 Bounder , 20 year old Dometic, "eyebrow" control board at top
Uses 12v to control every thing, yes even LP
No power means no worky
Almost every fridge from around 1980 up
Has electronic controls
Power usage is not heavy, but it is constant, and has too be considered

[SoundGuy]

steveh27 wrote:
My 2310 Dometic fridge on propane draws no electric. It is 20 years old.

So yours is a manual light fridge ... but what has that got to do with the OP who as far as we know has a conventional DSI fridge? :h

[steveh27]

My 2310 Dometic fridge on propane draws no electric. It is 20 years old.

I have a 105 AH house battery in my Class B. I can get by with my 120 watt portable solar suitcase.

[SoundGuy]

Almot wrote:
Classical case of incomplete information in the post #1.

ohhell10339 wrote:
Classic case of unwarranted assumptions. The fridge would run on propane, like it's designed to do.

If we're talking "assumptions" yours would be to assume only your fridge fan requires 12 vdc to operate when in the gas mode. This isn't the case at all as the main circuit board, ignitor, and gas solenoid in modern DSI fridges all require 12 vdc as well. Most gas absorption fridges also have a climate control heating element around the freezer section - some have a switch to turn this 12 vdc heating element off when dry camping but increasingly it seems manufacturers have been deleting the switch, meaning there's no way to eliminate this draw down on the battery. Mine is like that so I added my own switch for those times we may find ourselves camping without shore power and want to conserve our battery reserve as much as possible.

[MrWizard]

do as you please..
advice is offered based on experience. and differs from your idea that 100w portable is enough to do what you want
you can choose to ignore advice
but is impolite to argue that what you are presenting is the right idea, and will work, when you ask for opinions and advice
IF you are so convinced ? why ask ?

use always varies
but if you want to plan smart
you plan for the Maximum use, not the least amount of use

I doubt your parents had cellphones and laptops, i bet the fridge controls and other items also used less battery power than your trailer

and the alternator in the class C, was a lot closer to the batteries than the umbilical running to your trailer from tow vehicle, and did a better job of charging, than your T/V will ever do, with out modifications

[Almot]

Harvey, - no, 🙂 in a kayak I slept only once when there was no choice. By "tent in a kayak" I just meant that tent in a kayak was all the "rig" at that time. Tent was carried there, but for sleep it was set ashore.

It's difficult to help in situations like the OP. Fridge would run on propane as it's designed to do. Right. 12AH a day in my Norcold, in addition to propane. Still no info on equipment, and run time will vary.

Alright, here is an honest answer to the question of whether a 100 watt portable solar array will do it, or will he need 200:
Maybe yes, maybe no, results will vary depending on equipment and run time.

[ohhell10339]

Almot wrote:

Classical case of incomplete information in the post #1. What lights, what fan, how many hours on fan, how many hours on laptop, what is the fridge daily draw? He'll get 10 answers from 10 people, all different. The fan alone can easily consume all that 100W would harvest, and more.

Having said this, - solar does have an inherent inaccuracy in estimates, and it's better to err on the higher side and install more than you "think" you need. I would go for at least 200W, preferably 300W. On the roof - because it's a pain dealing with more than 100-120W portable.

Classic case of unwarranted assumptions. The fridge would run on propane, like it's designed to do. While I may run the fan occasionally, it won't be that often or that long. The hours I will use the laptop and the lights will vary, as I said. Therefore, to state one definitive amount or duration would be meaningless.

Roof solar has a number of disadvantages. One is difficulty of access for cleaning. The worst, though, is that you cannot park in the shade. Also, you can't easily adjust the tilt or angle of a roof-mounted panel. There is the positive aspect of the panel charging while you're driving during the day, but your rig's alternator is doing that anyway.

Now that I recall, my parents had a single 100 watt panel on the roof of their Midas and it appeared to be sufficient for them.

[Harvey51]

Almot, sleeping in a kayak is amazing! I have to get out and walk around every hour.
We never used a generator either but lack of charging power and ignorance of battery state of charge measurement did result in our first RV batteries only lasting a year. I fully understand many RVers will need more than 100 watts. But I am sure 100 will be adequate for quite a bit of laptop use. The portable panel would also be useful charging on hikes and at powerless jobsites but every RV should have at least one panel on the roof or walls.

Ther you go ohhell - start easy with one panel or go all out with 2 or 3.
If the former, do keep additional panel(s) in mind when locating the first one and get a charge controller good for at least 10 amps.

I see at least one instance in this thread of posters confusing the units of electric current (amp) and energy (amp-hour) which is like cancer, spreading confusion to new people. I'm sure the "DC side of life" website can sort that out.

[Almot]

Harvey, I have never used a generator when camping BEFORE I installed solar; have never plugged, either. Because it was a tent in a kayak. 🙂

Classical case of incomplete information in the post #1. What lights, what fan, how many hours on fan, how many hours on laptop, what is the fridge daily draw? He'll get 10 answers from 10 people, all different. The fan alone can easily consume all that 100W would harvest, and more.

Having said this, - solar does have an inherent inaccuracy in estimates, and it's better to err on the higher side and install more than you "think" you need. I would go for at least 200W, preferably 300W. On the roof - because it's a pain dealing with more than 100-120W portable.