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What size battery? Voltage and Amp Hours?Originally Posted by JackRyan
As gnihcraes asked, how fast do you want it to charge? FYI, a panel laid flat on the roof of a camper will not provide it's full rated output, so charging will take longer than expected based on panel rating.
I'll have to look. Might go with a golf cart style battery. Im not sure what came with the camper. I know the light are powered by it, but not funtional. So might as well up grade.
Are you saying you will get better power from a panel if its on a stand as to being flat?
Sealed AGM Gel Golf Cart Battery 12 Volt 35 Amp Hour
Sealed AGM Gel Golf Cart Battery 12 Volt 35 Amp Hour
35 Amp Hour is pretty small, I feel like a 100W panel would be plenty for that. Remember, you can only charge a battery so fast, so having 10 x 100W panels wouldn't work as well as one might think.
"There are no finger prints under water."
That would have enough power for the night? couple lights, might add small tv and dvd player, watch a movie, charge phones and tablets.
I don't know about adding a TV and a dvd player. For LED lights and charging phones and tablets, I'd say you'd be alright. Especially if you charge the phones during the day. I'd just watch the movies on the phones/tablets.
"There are no finger prints under water."
True....i might go 2 100 w panels and 2 deep cycle batteries. Expandable to 3 panels maybe over kill. Forgot to mention CPAP machine is a must. Go though on tablet regarding movies. thats what we did last trip with power banks for all.
A solar panel is most efficient when it is aimed directly at the sun.
In the random google image I have linked, you would want the panel aimed along the dotted yellow line.
The Elevation Angle of the sun changes daily, so you without an active tracker you won't get optimum sun all the time.
A good rule of thumb is to point your panel towards the equator at an angle equal to your latitude. 40? for the front range near Boulder. This is sort of a "happy medium" for a fixed installation between the high summer elevation, and low winter elevation.
So, to figure out how much loss you will have from laying it flat, there are two things to consider.
1. The difference in production at "Peak Sun" between a panel properly aimed at the sun and a panel installed flat will be ~15%. Your 100w panel is now only an 85w panel.
2. The duration of "Peak Sun" is significantly less with a flat panel, especially during the winter months with low elevation angles.
As for batteries, you need an idea of how many watts your lights draw, how long you want to be able to use them without damaging your batteries, and how fast you want them to recharge.
Golf Cart batteries are excellent options as they are built for frequent charge/discharge cycles, and to handle heavy current loads. This means they have thicker and heavier lead plates in them, which makes them last longer. Normal truck/car batteries actually kind of suck, as they are designed for very short but huge current draws (starting) and then they sit.
That's not a very large battery, so if you have room to go larger, I would. Depending on where your battery lives, I would stick with the Sealed batteries, but it's not a problem as long as you understand that a flooded/serviceable battery will release hydrogen gas when charging.
With standard AGM, Lead Acid, etc batteries, you only want to use from 100% to 50% of the capacity, or else you will damage the battery and reduce it's capacity and longevity. Li-Ion is better, but requires more expensive charge controllers.
So, If we take your 35AH battery, and plan to only use 17AH out of it before recharging, you only need to replace 17AH before using the lights again.
In CO the "worst case" scenario for solar is a max of 4 hours of "good" sun per day (obviously much more in the Summer).
A 100w 12VDC panel will provide ~8AH for every hour of "good" sun it gets. This means, in 4 hours, you are going to get 32AH of production.
The advantage to a good quality solar controller is, they won't over charge (also bad for batteries) your batteries. They will let the batteries float when they reach max capacity, and essentially waste the solar panel production beyond that point.
So, you can go as small as a 60w panel to recharge your 35AH battery from 50% with 4 hours of sun.
I personally would go with a 100w panel, unless you are going to go larger on your batteries, and then you need to re-address your panel size.
This is all subjective on the draw that these devices have.
TV's are power hungry pigs (relatively). I agree with Irving on using the tablets/phones for watching a movie while camping.
You also have to consider the losses incurred by running an inverter to create 120VAC to run your TV, DVD Player, Etc.
Charging phones and tablets during the day, when you are likely to have an excess of solar, is a great plan.
The size of your system depends on the space and weight you are willing to put into it, and the power that you need to use.
Your CPAP Machine should have a current spec on it's power supply (look for input voltage and current ratings on it - something like 120-240VAC @ .5A (random numbers)). Figure out how much power that wants, add in charging 2-4 phones at ~3AH/ea, 2-4 tablets at ~6AH/ea and you can start to build a power budget, and then spec your batteries and your panels to support your wants.
Once you get all that started you also need to think about if you want to be able to go a day or two without any usable sun (camped in the shade of trees, cloudy rainy weather, etc), and then you get into scaling your batteries and solar for surviving multiple days and how long does it take to recover when you do get back to sun?
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