Yet another new project>> we install 290 watts of solar power

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Outstanding work John! Now you will have to start boondocking more! So with all that power on the roof, what will that allow you to run, and for how long?
 
Nice job John.

Where did you install the additional battery bank and how are you charging them from shore power?
 
Heglmeier said:
Looks good John.  Do you even have room on the roof for another panel?
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Pretty sure I could fit another panel opposite the new ones, but I would have to remove the little 10 watt Winnebago installed panel (it's fairly useless anyway.)

SargeW said:
Outstanding work John! Now you will have to start boondocking more! So with all that power on the roof, what will that allow you to run, and for how long?
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Thanks Marty!  I'll be running some tests here at the campground - I'll shut off shore power, flip the inverter breakers off except for the fridge and see what happens.  We don't boondock very often and don't think I have enough solar capacity to be completely self-sufficient.  I look at the panels as an adjunct source of power that will reduce gen run time when we do boondock.

I did shut off the Xantrex charger for an entire day (during daylight) and the panels had no problem supplying all of our 12V needs - we made no effort to conserve energy and left the florescent ceiling lights on as usual.  Of course there would be a difference with the inverter running.

Harry B said:
Nice job John.

Where did you install the additional battery bank and how are you charging them from shore power?
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Thanks Harry!  Same house battery bank but with higher capacity Lifeline AGMs - 125 amp/hr vs. 105 amp/hr so I have 375 amp/hrs of capacity (the Lifeline dealer said the new 31XTs are conservatively rated.)  If we were really into boondocking, I'd add another couple of batteries somewhere.
 
Shoot, John, you've got plenty of room on the roof for more panels :)  But do you have room for more batteries? That's what we need right now, more batteries.

Wendy
 
Adding more batteries would be a bit of an engineering challenge  :eek:.  One possibility would be to install 31XTs for the two chassis batteries - they have 650 cold cranking amps at 0 degrees so they would work fine for starting the engine.  I could bridge the two banks together when boodnocking but then there's the risk of running down five batteries and not being able to start the engine or gen set (it's a small risk though.)

In thinking about this, there isn't much point in adding more batteries if the panels don't have the capacity to top off the battery bank during daylight hours.  We might be sized correctly now - further boondock testing is required.
 
Howard Rawley said:
Good project, nice write up.

Thanks John!

Howard
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X2

It looks like you are getting some significant shading on the one panel with the dish up, but I guess when you are boondocking you probably have more options on how you park, than in an RV park.

The standard formula is to have one watt of solar power for each amp hour of battery, but I believe it should be closer to 1.5 watts for each amp hour of battery.  This setup will certainly help cut down generator time when boondocking!

Paul
 
Thanks Paul.  Yes, a little shading from the rear TV dish, but not a big deal - it can be lowered with the push of a button if we need to squeeze every last amp out of the panels.

So we are then a little undersized for our battery bank.  One more panel will bring us up to 435 watts which would be closer to ideal, but that extra panel will have to wait - we've blown the coach budget for the year.

Almost 4PM here, high smoke overcast, scattered clouds and 7.0 amps out of the panels  :).
 
I would be curious to know how much the shading on the panel does cut down on output.  I have read that it can be significant, but have never seen any real world figures.

Paul
 
Boy, you have no idea how helpful this write-up has been John. As Cyndi and I continue to shop for our "retirement RV" the issue of solar panels and residential refrigerators has been a big concern of mine. We enjoy boondocking so solar is definitely in our future. Exactly how much is the question.

I don't mind running my generator, but if I can significantly reduce the need to do so with solar, it's worth it to me. Something about that quietness appeals to me. I can't wait to hear future updates on your system's real-world performance.

Kev
 
We added solar panels and batteries to our coach for the quietness factor more than the cost factor, and it's been worth it. Of course, it does make a difference in deciding on campsites....trees, direction, etc. And if you climb up on the roof and tilt those panels toward the sun, wow, what a difference that makes !

Wendy
 
Great Job!
  I know how difficult it is to design and install a system. So many conflicting views. So much misinformation online. It hard to separate the wheat from the chaff!

A while back I wrote a series of articles or the RV Newsletter documenting my process..from design to research to build.

You can view it here:

http://www.thewanderman.com/2011/11/better-solar-charging-mouse-trap-part-1.html

Next up is a better battery bank, hopefully based on Lithium Phosphate cells. I have really NO space for extra batteries. I am looking into replacing my single start battery with a same type/size deep cycle. I did some research on that and most folks agree that the low amp draw spread across multiple batteries should be fine.

Here's that info:

http://www.thewanderman.com/2012/08/why-cant-you-use-deep-cycle-batteries.html

Stay tuned, I am going back to the Lithium Phosphate well since the price has been dropping. 400 ah for around 2k. Much more cycles and discharges to 20% remaining so the math is beginning to work out!

Rich "The Wanderman"
 
Nice project, John - let me know when you install an "Auto-Pilot" on your rig, that's the update I'm waiting for.  :)
 
Very Interesting!  Thanks for the write-up.

As it happens, we just today went "live" with 5.3 Kw of solar PV on the roof of the "carport" where we park the RV.  There are 22 panels of 240 w each up there with a 6Kw inverter in the garage.  With tax credits and REC we hope to net out about $3/watt, maybe less, depending on our usage and the utility rates.  System should breakeven in 8-10 years and after that it makes a modest return.  BTW, you should get 30% rebate tax credit on your federal taxes for the solar system on your RV...

We are not full time RV'ers so the fixed system seemed to make sense for us.  Whether we are here or not, it's gonna be cranking out the Kw-hr's.  This will more than off-set any diesel fuel we burn as well as gasoline, JP4 and coal from the utility. 

Now the noise reduction is a big factor for installing panels on the RV someday.
 
Thanks everybody!

Wendy, I would love to have panels that could tilt!  On our sailboat, I had a single 50 watt panel that I could tilt, but the most current we ever saw from the panel was 2.5 amps at 10 degrees of latitude.  The modern panels are incredibly more efficient.

Rich - never heard of Lithium Phosphate - I'll have to familiarize myself with that technology.

Tom - the one huge difference between sailing and RVing is the lack of an autopilot  :p.  We had a state-of-the-art below decks autopilot on the boat which made those long passages very tolerable.  At night when I was on-watch I would be at the nav station keeping an eye on the radar, our course, and reading a book.  Not bad. 

With the coach, our autopilot is organic - I call it "Jane."

taoshum said:
As it happens, we just today went "live" with 5.3 Kw of solar PV on the roof of the "carport" where we park the RV.
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Way cool!  I did the math on wind or solar for our place in Texas and the math didn't work out for us - too long of a payback.
 
To semi-quote the most frightening movie ever (Jaws), you're "gonna need a bigger RV"!  ;D
 
Kevin Means said:
Boy, you have no idea how helpful this write-up has been John. As Cyndi and I continue to shop for our "retirement RV" the issue of solar panels and residential refrigerators has been a big concern of mine. We enjoy boondocking so solar is definitely in our future. Exactly how much is the question.

I don't mind running my generator, but if I can significantly reduce the need to do so with solar, it's worth it to me. Something about that quietness appeals to me. I can't wait to hear future updates on your system's real-world performance.

Kev
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For anyone wanting to learn more about solar, here is the best website I have found:  http://www.jackdanmayer.com/rv_electrical_and_solar.htm

Paul
 
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