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Old 11-08-2019, 04:40 PM   #1
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How much is too much? Solar I mean

We plan to have an all electric, power hungry coach. Two ~3000 watt inverters and 3 15k air conditioners, induction cooktop, convection micro, in house laundry etc etc.

We also plan to be in trees, up north (ish) where "the sun don't shine" etc. So my thought is to over provision the panels as much as possible knowing our success of sucking power in will be limited a bunch of times.

I haven't done the math yet on amp hours as we haven't narrowed down the actual coach. I also realize that AC, dryers, ovens and such are major power hog. Reality is that we'd likely never do laundry without power or generator, use the convection micro somewhat limitedly and cook top to boil water or short times. The DW despises generator noise but loves to be out in the woods boondocking. Makes it tough for me to accommodate both needs for a week or so at a time.

Anyway presuming I coat the roof in panels with as high a watt rating as I can buy, is there ever a time when that is too much? And yes I'll probably replace the L16 or 8D with equivalent physical size (but hopefully much higher useable amp hour) LiFePo4 batteries to store whatever we can get.
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Old 11-08-2019, 05:20 PM   #2
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I managed to put 1405 watts on a 19 foot roof with some effort. I had to use higher brackets to clear some stuff. I moved a TV antenna out of the way and mounted a large panel over the rear roof rack and bathroom vent. I changed out my 13500 BTU air conditioner for a much more efficient 11000 BTU air conditioner. I can run my air conditioner now under full sun 7-8 hours a day without depleting the batteries. My trailer has no slides and is well insulated without too many large windows. This helps reduce the amount of time the air conditioner compressor has to run each hour.

You need to consider your total capacity for additional weight, available space on roof, using enough large conductors to bring amperage down to MPPT controller(s). You also need to consider you battery storage system. I use four BattleBornBatteries 100 amp hour batteries.

Two 3000 watt inverters is a huge load on a battery system.
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Old 11-09-2019, 03:53 AM   #3
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Here is a link to the first of 11 videos this person did with a large install...Victron equipment (2 3000w inverters), prismatic cells, solar.

Might be worth a watch if you have the bandwidth plus there are parts you can skip ahead.

https://youtu.be/qD35LupYG-0
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Old 11-09-2019, 08:02 AM   #4
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We also plan to be in trees, up north (ish) where "the sun don't shine" etc. So my thought is to over provision the panels as much as possible knowing our success of sucking power in will be limited a bunch of times.
Figure about a 10x reduction in capacity when in the shade. You're not making that up in panel or battery volume, so operational accommodations will need to be made. Things are getting shut off or the generator runs.

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Old 11-09-2019, 01:30 PM   #5
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Remember, if you want to run power hungry equipment on 12 volts you will need very heavy wire the on the battery side of your inverter. A 1200 watt microwave will pull 100 amps at 12 volts.
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Old 11-09-2019, 01:57 PM   #6
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If you want to be in shade you need some portable panels.
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Old 11-09-2019, 06:50 PM   #7
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I’d say 2000W or buy the wife some noise canceling headphones and run the generator. Like you, I often park in the shade so I do not have to run the generator for AC. I DIYed 900W of solar (700W tilts) and in good sun on a cool day I’ll get 5-6KW out of them...most days only 2-3KW. At home 5.5KW is 70cents of power so maybe $1.50 to run my generator. Since we only dry camp in the summer for maybe 30 days saving $1/day I’ll pay for my solar in 40 years and my all in solar cost was only $1.25/watt...panels and 100A FlexMax mppt controller installed.
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Old 10-17-2020, 09:00 PM   #8
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We plan to have an all electric, power hungry coach. Two ~3000 watt inverters and 3 15k air conditioners, induction cooktop, convection micro, in house laundry etc etc.
Ugh. Why plan to do such a thing if you want to boondock? IMO boondocking requires propane and lots of panels/batteries, and/or a tolerance for living a more primitive lifestyle. Expecting otherwise will almost certainly result in disappointment and an empty bank account.

Quote:
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We also plan to be in trees, up north (ish) where "the sun don't shine" etc. So my thought is to over provision the panels as much as possible knowing our success of sucking power in will be limited a bunch of times.
Yes, cover as much of the roof with them as you can. You will still get some power in the shade.

Quote:
Originally Posted by Driveby View Post
I haven't done the math yet on amp hours as we haven't narrowed down the actual coach. I also realize that AC, dryers, ovens and such are major power hog. Reality is that we'd likely never do laundry without power or generator, use the convection micro somewhat limitedly and cook top to boil water or short times. The DW despises generator noise but loves to be out in the woods boondocking. Makes it tough for me to accommodate both needs for a week or so at a time.
You don't want to do the math, it will be ugly. A/C is difficult to achieve but up north you won't really need it much. Furnace/cooking is simple with propane. Refrigeration can be done with propane also though there are some very efficient electric compressor fridges that work well off-grid. I despise generator noise also so I will only fire mine up in emergencies. That rarely happens, but I am careful with my usage. I have only a single 1200W sine-wave inverter and I use propane for heat and cooking. I have 900W of solar and 420AH of AGM batteries.

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Anyway presuming I coat the roof in panels with as high a watt rating as I can buy, is there ever a time when that is too much?
NO. :-)
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Old 10-17-2020, 10:02 PM   #9
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Buy a coach with a very quiet generator, in a hush box if possible. You will need it for dry camping in the shade. Lithiums are a must because they will take full charge until full, way less run time that lead acid.
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Old 10-18-2020, 12:15 AM   #10
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I'm in the camp of putting as many watts on the roof as can practically be accommodated. There are many variables to PV production. Flat mounting reduces 10-15% from specifications. Low january sun increases that to nearly 50%. Additional limiting may be self shading from other items in the roof. So more is better.

Imho.
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Old 10-18-2020, 01:07 PM   #11
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We have 2925W of solar, and sometimes wish we had more. Go with as much as you can fit. Consider at least 24V, if not 48V.

The math doesn't really work out with rooftop AC units for extended use (this statement applies specifically to any unit requiring triple ACs, and most requiring double) - they're too inefficient. You can cool your rig for a few hours at a time, but won't be able to set the thermostat and just forget about it with current panel technology - you will run into a deficit even in optimal conditions. That requires more efficient AC units - with mini-splits, it's possible.

Everything else should be more or less "use as you want" once you are in excess of around 2kW, even in moderately shaded winter conditions, assuming you have a large enough battery bank to get you through the night and aren't using resistive electric heat.

I recommend as much solar and battery as you can afford, and integrating your generator with the system so it'll automatically start or stop when specific criteria are met. You can build a pretty low-hassle, automated system that just about handles all the details for you.
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Old 10-18-2020, 02:44 PM   #12
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Old 10-19-2020, 04:21 PM   #13
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Old 10-21-2020, 04:19 PM   #14
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There might be a limit .........

The only limit of concern will be the battery charge current limit. It's very unlikely to be a problem, but it's worth a quick check. You don't want the bms cutting off the charging.

Is a mini split an option? I.e., do you have a place for the outdoor units?
They are not expensive and their reduced battery and solar requirement might even pay for them. They are hugely more efficient than the best roof top units. Much much quieter. On a larger RV a two-zone mini split works though two single-zone mini splits will be even more efficient. One can heat with them in winter when the sun is good.
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