Our solar hardware has arrived, and we are working on assembling the components. I am not a carpenter; I am a low-voltage wiring chick… Rock is not a carpenter, either. You’ll have to pardon the third-grader carpentry skills.

Allow me to share a few things that I have figured out…

  • There is a LOT of DISinformation out there. Holy crap!
  • There is a lot of MISinformation out there. Holy cow!
  • There is a lot of missing information out there. Holy shit!

Basics

We plan on not relying on external power sources at all, if possible, so this is what our setup is going to look like.

To start, you kinda need an approximation of how much energy you will actually need on a weekly basis. Sunshine doesn’t happen daily, aim for every few days.

As an example of how the conversion chart works, let’s assume a solar panel rated at 60Watts, 12Volts and 5Amps.  The formula for Watts is Volts times Amps.  To use the chart, cover the W in the chart with a finger and use the remaining visible chart calculation of V multiplied by A.  Using our sample panel data, 12 Volts multiplied by 5 Amps equals 60 Watts.  W = V x A  The formula for Volts is Watts divided by Amps.  To use the chart, cover up the V with your finger and use the remaining chart calculation of W divided by A.  Using our sample panel data, 60 watts divided 5 Amps equals 12 Volts.  V = W / A  The formula for Amps is Watts divided by Volts.  To use the chart, cover up the A with your finger and use the remaining chart calculation of W divided by V.  Using our sample panel data, 60 watts divided by 12 volts equals 5 amps.  A = W / V
Easy calculations of power. Taken from Wikipedia.com As an example of how the conversion chart works, let’s assume a solar panel rated at 60Watts, 12Volts and 5Amps. The formula for Watts is Volts times Amps. To use the chart, cover the W in the chart with a finger and use the remaining visible chart calculation of V multiplied by A. Using our sample panel data, 12 Volts multiplied by 5 Amps equals 60 Watts. W = V x A The formula for Volts is Watts divided by Amps. To use the chart, cover up the V with your finger and use the remaining chart calculation of W divided by A. Using our sample panel data, 60 watts divided 5 Amps equals 12 Volts. V = W / A The formula for Amps is Watts divided by Volts. To use the chart, cover up the A with your finger and use the remaining chart calculation of W divided by V. Using our sample panel data, 60 watts divided by 12 volts equals 5 amps. A = W / V

Using your KillAWatt gauge, collect information of what you absolutely CANNOT live without over a month. Figure out what it uses and for how long and how frequently. Gather WATTS and AMPS and VOLTS. Nothing works with ONE number; they all use something different!

For example:  A standard iPhone 4S charger uses 5 volts, 1.0 amps, 5 Watts.  You will need all of these numbers eventually in your calculations.

I used a simple spreadsheet in Excel and just assigned it a priority rating of 1-4  — with 1 being “Imperative”, 2 being “Need”, 3 being “Want” and 4 being “Won’t Make The Cut”… Columns for W, A, V, Priority, Duration. Maybe I can share my spreadsheet, I’ll see if I can clean it up and link it on here.

We put sticky notes around the house. We annotated every light switch we clicked on and every power strip we turned on. Electric shavers aren’t used daily for us. Coffee’s hot water IS a daily. TV was logged in hours, as was the computer, laptop, iPad, phone(s). That night table lamp that is on for five minutes at bedtime, that end table lamp that comes on with the timer at dusk and is on for 12 hours. Ceiling fans in every room. Washing machine and dryer that you use every other day… You can figure out where to put your note pads!

Powah

Next, you need to work backwards. Use (based on the spreadsheet KillAWatt entries you figured out) to get storage, then what you can create. Or Batteries, and 12V Supply & 120V Supply, then solar panels.

Storage on batteries is rated as AMP HOURS… if the battery you are looking at is rated as CCA or Cold Cranking Amps, its is a STARTER Battery, not a running battery. Pick again. You want aH or Amp Hours! An AmpHour is ONE Amp for ONE Hour, which is often referred in Battery Speak as a 20-Hour Rating. (Reference: One AA battery is about a 2 aH battery. Car starting batteries are about 50 aH.)

My Dad is an Electrical Engineer, so I have grown up understanding a lot of this – – I can read electrical schematics; HOWEVER, that does not equate to “I know what I am doing.” But what it DOES mean is, “I can translate pretty well.” Caveat Emptor: Your Mileage Will Vary! (If you are seriously lost, please, please, please, consult with someone who knows what the crap they are doing! Some of this gets spooky. You can hurt yourself, or cause a fire if you aren’t paying attention to all the details.)

We calculated what our monthly use was around the house, prioritized by necessity. We then figured out what we wanted to be able to store (even if we went three or four days without sunshine), and then we calculated from there what we could reasonably (room on the van roof and available sunshine for our area) create from solar panels that we could afford. (Remember: this is a FRUGAL Build.)

Power Itself

Power in a RV, car, van, or cabin can be supplied in either DC (direct current, like a car’s cigarette lighter) or AC (alternating current, like city power in a house) and they are hugely different.

Batteries and solar panels come in divisions of 12 Volts. 6, 12, 24, 36, 48 volts. 12 is the easiest to divide, and the parts and pieces are the cheapest and most readily available. Boats, cars, and many RVs run 12 volt.

If your favorite coffee pot or toaster oven plugs into a kitchen counter socket, it is a 120 Volt AC power. You will need an INVERTER. This will lose you about 10-25% of your power in the conversion from solar’s DC power to AC power… and again, anything using electricity to make heat, is a poor choice. Plan accordingly. (Plan for propane, solar oven, fire pit, rocket stove, Kelly stove, or whatever you choose for heat, when possible.) You might need a couple things in AC, perhaps, but be very judicious in what you plan on running as AC current. (My desktop computer needs AC and I will not give it up. This may change in the future.)

AC Power is Not All Alike

Making the conversion to AC power from DC solar power is not to be taken lightly. You lose a lot in the translation. If you MUST use AC, then look at what it is you are taking… I am taking my computer and a 42″ screen on which I look at my computer. These are “delicate” items who require “Pure Sine Wave” power. That means that their power needs to be clean. Special. Fancy. Buy a Name Branded inverter that is called “Pure Sine”, not “modified sine wave.”

Non-delicate items do not need Pure Sine Wave. Chances are, your electric shaver or coffee pot doesn’t care…

YMWV!

We came up with:  220 Amp Hours in two 12V 110 aH batteries, a 1000 Watt inverter for 120V power (we probably won’t ever use the full capacity, because they’ll drain our little battery bank too quickly but it has room to grow with better panels and more batteries later), with a 100 amp fuse box for the 12V little stuff, two 150 Watt 12V solar panels (all we can afford right now, and they are about 40″x40″ in size), and a tie-in with the van’s 150 amp alternator for emergency charging to the “house” batteries. (In South Texas, we get a good solid 4.5 hours of real decent sunshine on most days. Winter for us is about 3 hours, Summer approaches 7 hours. Your sunshine may differ.)

These folks have a very generous sun-hours calculator. I find our numbers are about an hour less than they suggest.

Wholesale Solar’s Sunshine Calculator

What this Means for JUsT

This means that we have purchased about $1,200 worth of goodies! No joke. I about fainted. Rock had to poke the Purchase Button because my frugal finger couldn’t… We are frugal, and slipping the crowbar in the ol’ wallet for this was painful, but necessary. Solar panels have a 25 year life, and we pay $106 monthly for power in the little sanctuary were we are currently living… so in one year, we will have paid off the investment. It is frugal. Albeit painful.

I am a very big fan of Renogy, and we purchased their MPPT Controller and their solar panels, but we did not select their monitor. More on that, later. It is almost 5 a.m. and I am pooped… LOL!

Hardware

Renogy 150 Watt 12 Volt Monocrystalline Solar Panel

50′ solar cable Bulk Black copper #10 AWG 1000 volt PV Wire with Tough XLPE insulation

Blue Sea Systems ST Blade ATO/ATC Fuse Blocks

Renogy Tracer 4210 40 Amp MPPT Charge Controller, 12/24V 100VDC Input

Victron BMV-700 Battery Monitor

 

Next, we will discuss the inside of the van… outlets and ports and lights.

Later we will discuss the installation itself, including poking holes in the roof of the van and all the terror that involves.

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We would love to hear from you – drop us a comment below.

Tali

JUsT Us

2 thoughts on “Solar System, Part 1”

  1. Wow, that’s a lot of technical information! Sounds like your RV is going to be one hot spot 🙂 I think the investment is worth it. Short term pain for long term gain. Even us frugal people can deal with that. Awesome work guys!

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