Kelly and Laura’s Ascent into Solar Power…

Hello folks! This blog is dedicated to our experiences with solar electricity on the RVs we’ve owned and will own!

We spend most of our time in Colorado but take a couple of long trips each year. We prefer National Forest, Park and State Campgrounds. We are now self sufficient when it comes to electricity and can park almost anywhere. It wasn’t always that way! We started with a 21″ FunFinder travel trailer and dead batteries after several days of boondocking.

I did a bunch of research to figure out why and from reading HandyBob’s blog determined that I didn’t have enough charging capacity using the truck alternator. There’s a fairly long explanation as to why that is so but it boils down to not enough voltage and current to begin with coupled with a very long wire run from that alternator to the RV battery bank that exacerbates the not enough voltage problem even further. Bottom line: no way RV batteries get charged in a reasonable, or perhaps any, amount of time. What to do? Buy a generator? Not an option. We hate those things! Use candles? Ah, no. Stay home or always park in a campground with electricity? No. It turns out that a well designed and installed solar system is perfect.

Link to our RV Installations:

http://cuernoverdesolar.files.wordpress.com/2012/12/318sab-solar-install2.pdf

Photos of our adventures:

https://picasaweb.google.com/107468884836373763995

If you want to truly understand battery charging, solar installation, etc. and its nuances you must start by reading the HandyBob blog here:

http://handybobsolar.wordpress.com/

Handy is excellent! It can make your head hurt. I’m going to extend what he says into a series of simpler entries to help others down this path.

Thanks for reading and feel free to contact me if you have questions!

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12V vs. 110V Stuff

Since your RV is inherently a 12VDC system it makes the most sense to choose electronic items that run on 12VDC!  Sometimes, though, one stops thinking and does silly things!

1. Don’t invert 12VDC to 110VAC to power something that has a 12VDC option.  Think about your portable electronic devices.  Many of these have car chargers.  Use those instead of the 110V charger.  I have installed a couple of extra cigarette lighter outlets in our rig to facilitate this.  The one that gets used the most is by the desk…

2. Don’t necessarily buy a 12VDC option of something thinking you are doing yourself a favor.  The most common item is a 12VDC coffee maker.  They don’t work.  Spare yourself the expense!  The absolute best idea I’ve heard lately came from one of the folks I helped with a solar install.  Use your Mr. Coffee but instead of letting it heat the water simply pour hot water created on your stove into the filter!  Brilliant!

We have a 110VAC percolator that we use.  It pulls about 75 amps for about 10 minutes to make very good coffee.  I think that a traditional coffee maker might pull about the same but for less time.

Thinking back to electrical power basics: P = V * A.  So a 12VDC product will take about ten times the amps as a 110VAC product.  That means short heavy cable runs or products that use less power and therefore don’t get as hot or work as fast.

3. I am not an expert on CPAP machines.  That said I did do a little research as I’ve encountered folks recently that said they couldn’t do solar in their RV because they use a CPAP machine and they can’t run it all night.  My BS detector was immediately stimulated when hearing this so I thought I would check.

Many of the machines I looked at (OK, I looked at maybe three) had 12V options.  They all used between 25-300 watts with most using closer to the 25.  You will want to look at your machine to see what the specs are.  You’re back to the power equation.  If you can use 12VDC do that rather than inverting.  You will be more efficient.

As to the power required.  If your machine uses 120 watts (I picked that number to keep the arithmetic simple) they you will need 10 amps to run it on 12VDC.  If you run it for eight hours then you use 8 hours * 10 amps = 80 amp hours.  In my case that will be a bit less than 20% of my battery capacity (I have 440 amp hours in my four T105s).  The arithmetic will be similar for inverted 110VAC plus the inverter inefficiencies.  Maybe more like 90-100 amp hours.

Needing a CPAP machine does not eliminate your ability to have solar power on your RV.  One will want to have the most efficient model possible and use common sense!

4. This should be number one.  Turn off the lights.  Turn off stuff you aren’t using.  Do what we should always do: conserve.  If you have an inverter and it isn’t inverting something, turn it off.  If you have stuff plugged into inverted outlets that draws stand by power even when turned off, unplug it.  Think about LED bulbs instead of incandescent bulbs.  Heck, even HandyBob isn’t turning his nose up at those anymore!  LED strip lighting is inexpensive and does a great job of lighting up your rig and uses 1/10th the power.

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To Invert or Not to Invert, That is the question…

Almost all of the equipment in your rig runs on 12VDC power.  Most if not all of the lights, the electronics for the Fridge, stereo, heater, etc. all run on 12VDC.  If you are plugged into 110VAC in a campground the converter that is provided in your rig converts the 110VAC shore power into 12VDC to run all of these native 12VDC devices.  If you are not plugged in, power is provided by the battery or batteries in your rig.  In addition to providing the 12VDC power, the converter also acts as a battery charger, albeit a typically less intelligent battery charger than you need.

There are typically a couple of exceptions to the 12V rule: the giant Air Conditioner mounted on top of your rig, the microwave oven in your kitchen and perhaps a television.  These are all 110V devices that will only function if you have your rig plugged into 110V power.  They all have large power requirements (with the exception, perhaps, of the TV).  In addition to these standard items in your rig you may have also brought along other typical household devices like a coffee maker and toaster.  Again, these are typically large power users that require huge amps to run.

Back to some electrical power basics.  Remember that watts (power) equals volts times amps ( P = V * A ).  If you have a 1200W device, like a toaster, and you run that on 110V you need approximately 11A for that device.  If you want to run that same 1200W toaster on 12V you will need 100A instead.  100A is a lot of amps requiring very large cable to safely work.  The difference in wire size?  100 amps requires wire about 1/2 inch in diameter.  For 11 amps, that wire size can be less than 1/10 inch in diameter.  I have over simplified the discussion about wire size but it is illustrative if not completely, technically, accurate.

Wire size is why, way back when, higher voltage alternating current (AC) was chosen rather than lower voltage direct current (DC) for most of our daily household electrical requirements.  The size of the wire required in our homes is significantly smaller, and thus less expensive, at the higher voltage.  In Europe they chose 220V AC to further reduce their wiring requirements and in some cases we use 220V in our homes to power big things like our ovens and stoves.  These higher voltages were chosen to reduce wire sizes.  Why not even higher voltages?  What, you want to kill yourself?  110V shocks are sufficient and usually not fatal.  Higher than that?  Not so much…

But in an RV, having a portable source of 110V alternating current is expensive (and noisy and I think you know what I think about generators).  Enter the use of 12V wet cell batteries.  Batteries are relatively inexpensive and are also very efficient sources of electricity.  Unfortunately, they provide DC power at relatively low voltages.  Thus to provide lots of watts they need to provide lots of amps.  And they can only run those relatively small, low power devices, like lights, efficiently and without destroying themselves.  Drawing high current from a battery for long periods of time will destroy it.

Enter the inverter.  An inverter is the opposite of the converter, inverting 12V DC into 110V AC.  This is done using magic provided by a large, heavy, box.  OK, it isn’t magic so much as a bunch of electronics and some transformers cleverly concealed in a box.  An expensive box if the number of watts you want to create is large, say large enough to run your microwave.  I should mention that you will never, realistically, invert enough battery DC into 110VAC to run that giant air conditioner on your roof.  Don’t think about it, don’t try it.  If you need air conditioning, plan on parking someplace that has 110VAC.

There are basically two different kinds of inverters: Modified Sine wave and True Sine wave.  The differences are fairly arcane but relevant.  The more sensitive the device is to power, the more likely it is that you need True Sine inversion.  As you can imagine, True Sine is more expensive.  Most, if not all, electronic devices, like TVs, gaming stations, computers, really like True Sine.  Toasters, curling irons, etc., can live with Modified Sine.  You should probably rule out Modified Sine.  Modified Sine is less expensive but less flexible.

Inverters come in all shapes and sizes and prices.  Here is the key: if you are not going to try to run a large device, like the microwave, or a toaster, then think about getting a relatively small, True Sine inverter of sufficient size to run the device.  I have a 300W, True Sine that measures about 6″x4″x2″ that will run my TV just fine.  Cost about $100.  It has a fan and makes some noise but it does what I need it to do.  It plugs into a convenient 12V cigarette lighter outlet next to the TV.  The TV then plugs into it.  There are a bunch of choices for inverters of this size.  Spending a little more buys you a better inverter in most cases.

We also have a 2000W Magnum 2012 True Sine Inverter to run the big things.  That bad boy cost about $1700 and weighs 43 pounds.  It will run, ONE AT A TIME, the microwave, toaster, hair dryer, curling iron, crock pot, TV and DVR, etc.  It lives in the battery/solar/inverter compartment at the front of our rig.  It is wired into the 110V electrical system in the rig.  It also has a very precise battery charger so if your rig is plugged into 110V shore power, it can be used to correctly charge the batteries.  We don’t often use it to do this as we have solar to provide battery charging.  It is a sophisticated piece of equipment.  Installing the inverter and electrical wiring to support it cost about half of what my total system cost!  Just to be able to run those pesky 110V devices.

In order to support this large inverter, my system required four Trojan T105 6V batteries.  If you try to run a large inverter using a smaller battery bank, you will fry those batteries.  Period.  If you do not use large enough wire on a short enough run between the battery bank and the inverter, you will fry the wiring (and perhaps your rig).  Period.  We’re talking #3/0 or larger wire.  That is wire as fat as your thumb.  If you are spending $1700 on an inverter and $700 on batteries, why would skimp on wire?  Duh.

If you are contemplating a large inverter, read this:

http://handybobsolar.wordpress.com/inverter-issues-spring-2013/

Subjective, objectivity is what I call HandyBob’s notion of inverters.  You might as well benefit from his experience.  DO NOT BUY JUNK.  Period.

What’s the bottom line?  If you have the need to run those pesky 110V devices while in your RV, you need an inverter.  You should only buy what  you need!  If you only want to run your TV then you can get away with a stand-alone small True Sine inverter.  You will save money and you will save your batteries.  All inverters draw power whether or not they are providing power to a device.  The larger the inverter the more power you waste.  If you are not using 110VAC turn the inverter off or unplug it!

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Ken’s Install

Ken reached out to me via the blog several months:

“Good day_ Kelly and Thank You for this blog.

I have almost completed a Ford E250 hi-top conversion van boondocking project…The solar panels should be here in a few days. I have the battery box/vent in place, the 12v wiring for the fans, fridge and lights connected to the distribution fuse block. Here is my setup:

(2) 120w 12v solar panels in parallel #10 wire > Combiner Box #6 wire> Morningstar Tristar 45 PWM > 6v T105 in series #6 wire…

The Trimetric 2025RV 500a shunt, everything is real close…the run from the
roof is only 10′.

I did the daily power consumption math and came up with 60 amps…the ARB 12v only fridge is 30 amps a day…so 240w of solar 14amps x 5 hrs = 60amps, 225AH battery is a 30% draw down per day +/- 10% I should be good…on paper. I’m using LED lights and a Marine manual water pump…so beyond the appliances just want to charge Ipad, Cell and Laptop with a small 300W >500W plugin inverter (brand recommendation request).

I got the #6 welding cable off ebay precut with lugs for a decent price, 2/0 for the series battery connection and a braided ground. I’m putting in a 30 amp shorepower plug and have a Progressive Dynamics PD 9245 converter/charger ready to go, for the times I use an rv park or campground.

Now that’s as far as I want to go it alone.

My challenge is I live in Wisconsin and all you guys are out west. Do you or Handy Bob know of any solar installers that see things your way…that are within a days drive from the Milwaukee area (a days drive means maybe 400 miles)…I’ve put a lot of time in to this project and don’t have unlimited funds…just a regular guy…and would prefer an experienced hand to connect everything. All the dirty work is already done. The solar panels are going to be mounted on a Thule roof rack because my hi-top roof is full of curves. The benefit is the brackets will be side mounted so the only hole in my fiberglass roof will be the wire drop and good air flow under the panels.

I appreciate any ideas you guys have and I pretty much know what needs to be done just lack the experience to do it…so as far as labor cost for someone to help I could probably create a grocery list of what actions need to be taken and then I could get a pretty good estimate.

Thanks again_Ken”

As you can tell, Ken had a great grasp of all of this.  My immediate response was you can do the rest of this yourself.  If one is handy enough to put together their own conversion van one can certainly put this solar stuff together.

Over the next couple of days Ken sent me his wiring diagrams (HandyBob, you would have loved them!  He used MS Word rather than PowerPoint so they weren’t quite as purty but close).  We tweaked on a few things and got it just right.

Wiring Diagram (2)

I cleaned up the only error he had in the drawing: battery negative to chassis ground.

One of the issues most perplexing was the notion of chassis ground vs. negative.  We had a long conversation and got that squared away.  The long and short: in autos and RVs the manufacturer often (if not always) uses the chassis for the 12V negative and call this ground.  In the case of RVs the 110V grounds are connected to the chassis too (they can’t put the neutral 110V line there!).

The charge controllers and the inverters both have a chassis ground connection in addition to negative 12V.  We wire the ground with green wire and the negative with black (in a RED + /BLACK – scheme) or white (in a BLACK + /WHITE – scheme).  In RVs the green and the negative are often seen wired to the same post on the chassis, thus the confusion.  The real key for Ken and for all of you that are going to use a Trimetric (and that will be all of you) is to ensure that the only thing connected to one side of the shunt is the battery negative.  The other side of the shunt may well have a connection to chassis ground but that’s the only place!  Otherwise your meter won’t measure correctly.

So here are Ken’s photos.  As you can see he is a bit persnickety about stuff!  Second to mine his is the best install I’ve seen.  And he told me he was a big guy and had to stand on his head at times to hook things up!  This looks real good to me.  Oh, and if you are in the Milwaukee area and need help with a solar install on your RV, Ken’s your man!

photo01 photo04 photo03 photo05 photo06

Very efficient space utilization!

photo07 photo12

Highlighting the shunt to battery negative connection.  The small wire is the Trimetric connection.

photo15

I like labeling the sides of the AC disconnect!  Nice!

photo17

100% is good!

photo08

Note the strain relief that he added to the box.  HandyBob is doing that now with his installs.  Ken also put cardboard over the panels while he was working to keep them from being energized and blowing something out while he was working.  Did I mention that he was a bit persnickety?  It can’t hurt to do this during your wiring.  Sparks are not a good thing!

photo18

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Some Installs I’ve helped with… Tom B’s Rig

Like most of you, Tom reached out to me for some help.  I’ll let him take it from here…

“Finished installing the two panels today. I ordered SS mounts, but they didn’t work with the radiused roof on the Mountaineer. So my first attempt was to raise the mounting feet with blocks made from Trex composite deck material. I made 3″ blocks for the driver side mounts and 2″ blocks for the passenger side blocks.  They were hard to install and I didn’t like the result. So I bought aluminum angle and fabricated extensions to mount the second panel.

The down wire is pulled. There is a pocket door between the upper level bed/bath and the living space. There is a dead space between the pocket door and the shower in the bedroom and I measured about a zillion times before I bored a hole in the roof; hit is exactly. Fished the #4 jumper cable thru the roof and down to the basement via the large hole already there for the water supply to the shower. 

I already had the Magnum 2812 Inverter/charger and batteries installed in the basement on the driver side. Pic shows the black case for two of the batteries. The other two are to the left in the battery compartment (not enough room for all 4 batteries.) I have a piece of 3/4 in plywood thru bolted to the basement wall with one of the bolts thru a metal support. 

Next step is to mount the junction box on the roof, mount the A/C disconnect, power post and TriStar, Dicor all the roof penetrations, connect the MC4 cables and tie them down, terminate them in the junction box, complete the A/C – CC – Power post wiring, test polarity from the panels and throw the switch. 

I’ll send more pics when I’m finished. 

I woke up last night thinking about the install/operation of the solar system and realized I don’t know the answer to a rather basic question: Do I need to disconnect the solar system before connecting to shore power or starting the generator? I’m unclear how the CC and Inverter/charger would behave (blow fuse???) or whether the inverter/charger ‘knows’ the solar is present and charging the batteries?????”

As you can tell, Tom has a pretty good grasp of this!  In answer to his middle of the night “oh my gosh” comment here is what I told him…

No, you can leave everything connected.  They all play nicely together.  The amount of current that the batteries can take is determined by the voltage they are at.  So all the stuff that can provide current will but not too much.  The charge controller is actually the smartest thing in the setup.  Next is the Magnum and finally is the charger in your original Converter.  I would disconnect that one altogether.  Usually it plugs into the converter box someplace so simply unplug it.  When you are on shore power let the Magnum do the work.

When I’m plugged in I turn the Magnum off and let the solar do the work.  If you do that all the 12V stuff will take power from the batteries or solar all the time.  No 12V juice provided by the shore power.  The only thing shore power will run are 110V AC devices.  I like this as it makes me feel like I’m using my investment in batteries and solar even though I am connected to shore.  The only reason, really, that we connect to shore is if we are using high draw AC stuff for long periods like the air conditioner or an electric heater.  If we don’t need that stuff I don’t even pull out the cable.  I designed my system to provide enough power in the first place so why not use it?

Here are Tom’s photos.  Nice clean panel mounts…

P1020982 P1020983 P1020985

P1020984 I’m with Tom, I like this approach much better.  Obviously!  It looks like mine (OK, I’ll give credit, it looks like HandyBob’s…)

P1020986

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Some Installs I’ve helped with… Carlin and Wes’s Rig

Carlin reached out to me a couple of months ago from Las Vegas.  She and Wes planned on fulltiming in their RV and wanted a functional solar system.  Turns out their rig is very similar to mine and so my design would be perfect for them too.  They purchased most of their stuff from Northern Arizona Wind and Sun (a good vendor by all accounts) and arrived in Colorado just as Laura and I were able to get back into our home after the Black Forest fire evacuations.  Good news for us, though the fire burned under our trees on the north and east side of our home, we were spared.  Countless hours on the chain saw and hauling tons of slash paid off.  Hundreds of our neighbors were not so lucky.  Our hearts go out to all of those folks.

Any who…

I was fairly hands-on during this install though Wes and Carlin did all the heavy lifting.  They already had the panels up and attached to the roof when I arrived and had a pretty good idea about how to run the downwire.  After conferring they completed that aspect of the install and had the downwires in the battery/equipment compartment at the front of the rig.

RooftopWe had some fits and starts trying to fit all the equipment conveniently in that space but manage pretty well.

Panel

We had a very good and relatively easily accessible spot for the Trimetric and Magnum panels.

Trimetric

This was my third install so I’m gaining confidence.  HandyBob warned me that you will skin more knuckles doing this than you want to and he, as always, was right.  I think we did pretty good work on this one with few problems or missteps during the process.  Wes and Carlin could probably have done this by themselves but as a team we were much more efficient than we would have been separately that’s for sure!

HandyBob, you would have cringed at the site of the 55″ LED TV in the living room, but, heh, not everyone wants to look at a 20″ screen to watch football!  We spent a bunch of time talking about how to conserve power and I’m confident these guys will do just fine!

Several days later I got an email from Carlin and she was showing off.

Showing Off

36 amps isn’t bad.  I’m thinking it was that low because the batteries were already mostly charged!  This photo was taken at about 10:20AM.

Way to go guys.  Thanks for reaching out to me.  I enjoyed meeting and working with you.

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2013 Winter Journey…

We left Colorado on December 20, 2012 for our winter journey to Arizona and California.  The goal: to beat the Colorado winter.  We almost accomplished our mission but came home just in time for a blizzard and 20 degree weather!  Oh well…

The solar system we built worked flawlessly.  Though we were often plugged in to shore power (we had long stays in state and regional parks that had 110V) we used our base system for all 12V loads in the rig.  The winter was unusually cold so we used a 110V 1500W electric heater instead of the propane furnace.  This saved us about 30 gallons of propane a week so was worth it.  I didn’t want to break my boondocking mantra but it was expedient!

We had about 20 days of true boondocking out of the 70 nights of camping.  On those days we used propane heat when necessary and continued to use all of our electrical devices as when plugged in.  We have about 440 Amp Hours of storage.  We were down to 70% capacity a couple of times (per our Trimetric meter) when the sun shone the following morning.  In most cases we were back to 100% before lunch!  In fact, we rarely got to see the system perform at its maximum as the batteries were full before the sun was highest!  We routinely saw 20-30 amps into the batteries even while the sun was at low winter angles.  This was dependent on the orientation of the rig as well but we usually camp with our awning (and thus the solar panels) pointing to the southeast.

We installed several strands of 5050 SMD LED lights in the rig.  What a great addition!  These strips provide a ton of light without drawing much power at all.  I put one strip above our chairs shining down which effectively replaced the two incandescent fixtures for reading and one long strip above the main slide shining up.  That one provides very nice ambient lighting in the rig while only drawing about 2 amps.  I plan to put another string on the other slide and one above the kitchen sink.  You cannot beat these for great lighting!  I even sent 15 feet to HandyBob expecting a guffaw.  What I got instead was a photo of how he cleverly used them to replace his fluorescent bulbs in his fixtures!  And cut his power consumption for lighting!  And the boss loved them too!

We always think about the power we are using when we are in the rig.  We learned this winter that we did not need to worry about it!  Even on days when the sun was not shining normally we always charged.  We never had a day when we did not reach 100% charge.  Even on cloudy days the system delivered 10-20 amps.  We learned how many percent making a pot of coffee requires.  We know what watching TV all evening does to our capacity.  We turn off lights when we don’t need them.  We actually live smarter!  And we were a bit smug when others around us were having to run their stinking generators while we had all the power we wanted!

Thanks to the wife for making this a great trip!

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Solar System Main Connection Panel

The attached paper details the connections between the solar panels, charge controller and batteries.  There is enough detail in this paper for you to build your own main connection panel.

Solar System Main Panel

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