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[J.P.M.]

JPM , I'm not saying 15.83 'sun-hours'. that's the total peak 'daylight hours'. Not at all an insolation number. My site had a kit from EC on it the year before I bought it- the guy from EC provided me the summer/winter numbers of 7.8 and just under 3 , as my insolation numbers. I certainly don't have the skill to do that, but the Environment Canada guys surely did. At least, I would hope so. I think you're seeing the numbers and getting upset at the 'this is how long my daylight hours' last number and not reading where I am saying 'Sun-hours' or insolation numbers *7.8 peak in summer*, versus 'total daylight' - NOT insolation. And its a bit under 3 in the winter , which makes me glad that at this point, I"m not there in the winter.

Reality - my question isn't about load. not in the slightest. I have bigger loads coming ... ~5 years down the road. I don't know those in detail yet - but I"m more than happy and willing to rebuild a battery bank and move to 48V *at that time*. What I need to do is *get to 5 years down the road*. For the next 5 years, I am looking to hold up 2 people in a 25' trailer. We are using it for generally 3 days at a time, max. Daily consumption ~2-2.2KWh.

All the calculators I could run pretty much gave me a bank size of 600Ah. but getting this 804Ah bank turns out less expensive than the 6, and I don't have to parallel any batteries to do it - the 600Ah bank needs a lot of wires, big ones - and this bank only needs 2. That's a lot of stuff that I don't have to worry about. Also only 12 caps to check for water, compared to 24 if used 6V L16s.

My loads look like i should never exceed 20% DOD. I'm completely happy with that for the next 5 year window. Even if I've missed something stupid, and they go to 30% , I'm still happy; the battery bank is big enough to hold me up, and the input power SHOULD be enough to supply my *loads . 20% is ~4Kwh/day , if I did my math right; i'm only projecting half of that based on the stuff I have going into the trailer. So I'm pretty sure - for now, I left a lot of overhead.

What I don't know is if the 6x300Wh panels will be sufficient to run enough current into the battery bank to *charge* it effectively, because unlike calculating my loads or figuring out the amp draw, that number seems to be all over the map and its got me stumped. I"ve read that undercharging your batteries can be bad for them as well, and seen numbers indicating an ideal range; I"m not sure how to validate that I"m there specifically for current provided by array vs size of battery bank. I am putting a propane generator on, but obviously would like to minimize that use. If i need 2 more panels, good; if i need more than2 more, i'll spend the money on smaller batteries.

My math went 'assume 25% dod, thats 200Ah, thats about 4800Wh at 24v, lets not count on 7.8 , lets go with 5 on average for the days i'm going to be up there, and that gives me a panel size of 960 , lets use a factor of .6 for system losses, that gives me .. 1600. ish.'. So I think i can get sufficient power from teh 1800 watts of panel including system loss - but i'm still concerned that the incoming amperage might be low - do I NEED to get up to C/10 , or is a lower amperage inbound sufficient given the days of 'no use' in between our visits?

Don't know why you think I'm upset. I'm only seeing you with a lot of confused thinking and offering information. Take it or leave it, but in any case get less confused than you are now if you want a better design. Keep the cart behind the horse and learn more about the solar resource before you run off and wind up with a less than optimal or unworkable design due to ignorance of the solar resource. In the end it matters not a whit to me.

Assuming "EC" means Environment Canada, did that person provide an orientation for the surface that sees 7.8 (I'm assuming)kWh/m^2 per day in summer day or 3.0 kWh/m^2 per day in winter ? Looks to me like that's the 2 axis tracking insolation availabilities. You may be planning on dual axis tracking but know it'll be pretty expensive relative to a fixed surface ,and require a lot of maint. to keep working.

One last time: The number of daylight hours, or put another way, how long the sun is above the horizon at any location for any day, is mostly useless information. Don't worry about it. Pay more attention to the POA insolation for the surface type and orientation you plan on and learn and understand what you're doing.

Run PVWatts after you read the help screens for a primer in the solar resource.

Take what you want of the above. Scrap the rest.

[Ampster]

Don't know why you think I'm upset. I'm only seeing you with a lot of confused thinking and offering information. .......

Perhaps you are not listening to the OP and your persistence in pontificating is leaving that impression. FWIW, the OP has not seen you upset like I have. LOL

[Droo71]

4000W inverter. Overkill - but the price was completely right. LOTS of headroom.
I have a prewired panel to make sure I have the right sets of breakers and can easily organize and operate my setup and not make dumb wiring mistakes.
I have a 100A Charge controller, up to 224V input as configured, 100A output.
I have 1800W (nameplate) of panels.
I know my estimated DoD % on my battery bank; i used 25% (200AH) althoug the actual expected draw is only 100AH.
I ran my 'how much panel' calculation against 4800 watts to allow myself a healthy capacity margin.
I know my estimated draw on the batteries, in amps, to support my expected simultaneous loads, and I know the required wire sizes and battery bank size to support this. I'm oversized to that ,because the batteries I am looking at are comparatively cheap. As a result, my planned battery bank is 800Ah.
200Ah. of storage is 4800 watt/hr at 24v (and it is twice my estimated ACTUAL loads, but i figured i would be safe).

If I use 5 hours for insolation (which I did) - most of the months I will be there, I get 5 hours all but 3 months of the year - and I am not there for those months - 4800/5 = 960 watts of panel. If I assume 40% loss in the system , that still only takes me to 1600W - and the next largest number with the panels I have is 1800W to provide the power to replace my usage.

I don't believe I am out of the ballpark in insolation or estimate usage, and I've left myself about 100% of overhead based on my existing loads.

You keep telling me that I don't know my resourcing. A longterm solar evaluation was done on the lot to give me my insolation values, (it was done before I owned the lot, but I have the paper) I have an insolation value in Nov and Dec of 2.xx , all lower than 3. January 3.63 February - April is 5-6 May-August gets 6-8 September , October is back to 5-6
This includes tilt angles of 30, 45, and 60 , facing due south. There are recommended dates when I should adjust the panel tilt.

I am not worried about load. I am comfortable that I have sufficient insolation and panel to manage *MY EXPECTED LOAD*.

My concern is - 'given this setup, do I need more panels to ensure that I can reliably put a full charge into the batteries'. Instead, you keep insisting on telling me that I'm not getting 15 hours+ of max sun - which I know. And I"m not even counting on the 7+ in the report; I've used *5* as a number. Which I also stated already, although you seem to have ignored it.

All the other math I have listed above seems quite clear to me, I am really struggling with determining the appropriate *charge rate* to look for coming out of my charge controller into the battery bank. Everywhere I look seems to have different numbers on what I actually should plan for.

[Droo71]

Ok,
So I did run PVWatts.
I feel quite validated. FAR more power than I need for the next 5 years... assuming, as I asked in the first place, how much panel wattage I need to most efficiently/effectively/safely charge the battery.

PVWatts gives me a result - with my current system - of over 200Kwh/month from Mar - September.
My expected USAGE is 20Kw. I budgeted my panel size at 40Kw/mo. This is tons more than I was expecting to have available. And significantly more cost effective than pulling in the grid.

DC array Output (kWh)
143.8654938
185.3646851
255.9937286
243.4103699
246.793869
238.7581787
255.1073456
232.07724
214.4846191
154.8916473
124.7474213
109.3949966
2404.889595

[J.P.M.]

Perhaps you are not listening to the OP and your persistence in pontificating is leaving that impression. FWIW, the OP has not seen you bnb upset like I have. LOL

Well, perhaps you're not reading what a couple of other posters have written that are along the same line as mine with respect to resource availability. First things first. It might just be you are also ignorant of the resource and the importance of modeling a system. What you call pontificating some others call information.

Besides, the OP is always free to ignore what's offered, as he is free to see what I've written in the past.

[J.P.M.]

Ok,
So I did run PVWatts.
I feel quite validated. FAR more power than I need for the next 5 years... assuming, as I asked in the first place, how much panel wattage I need to most efficiently/effectively/safely charge the battery.

PVWatts gives me a result - with my current system - of over 200Kwh/month from Mar - September.
My expected USAGE is 20Kw. I budgeted my panel size at 40Kw/mo. This is tons more than I was expecting to have available. And significantly more cost effective than pulling in the grid.

DC array Output (kWh)
143.8654938
185.3646851
255.9937286
243.4103699
246.793869
238.7581787
255.1073456
232.07724
214.4846191
154.8916473
124.7474213
109.3949966
2404.889595

Well, aren't you happy you found PVWatts ?

If you're happy, I'm happy.

A respectful suggestion: Since Ampster is so adept at warning you about what he thinks is my pontificating, perhaps he'll be better at clearing up your apparent confusion about units. I sure wouldn't want to incite his ire by trying to tell you that your ignorance is showing and you add to the confusion when you use incorrect nomenclature as you do. Ask him to give you a lesson or two on units. You'll look less ignorant if you get them right.

(hint: Usage is in units of energy, that is kWh, not units of power as in kW. Writing "My expected usage is 20Kw (sic)" makes no sense. Another hint: Panels are sized in STS watts, not Kw(sic)/month. that unit makes no sense as a panel size whatso ever.

You want good and straight answers, communicate effectively and know the basics. That's basic good manners if nothing else.

Add: I'm done with this post. Good luck.

[SunEagle]

Ok,
So I did run PVWatts.
I feel quite validated. FAR more power than I need for the next 5 years... assuming, as I asked in the first place, how much panel wattage I need to most efficiently/effectively/safely charge the battery.

PVWatts gives me a result - with my current system - of over 200Kwh/month from Mar - September.
My expected USAGE is 20Kw. I budgeted my panel size at 40Kw/mo. This is tons more than I was expecting to have available. And significantly more cost effective than pulling in the grid.

DC array Output (kWh)
143.8654938
185.3646851
255.9937286
243.4103699
246.793869
238.7581787
255.1073456
232.07724
214.4846191
154.8916473
124.7474213
109.3949966
2404.889595

As JPM stated the usage is in kWh/month not kW and the panel array is sized as kW.

So I am not sure what kW array size you entered into PVwatts (1400W, 1800W?) to get that DC array output in monthly kWh but if the numbers work for you then go for it.

Just be sure you really understand the cost to purchase and maintain that 800Ah battery system. because you will need it if you get multiple days of little to no useful sunlight for your pv array to provide you the power you need.

[Ampster]

@Droo71,
You appear to understand the insolation numbers and I never worry about a few misplaced kW instead of kWhrs. Any calculations that are critical or involve a large purchase should be checked or reviewed for consistency.
I don't have much to add except to wish you luck as your dream evolves.There is a tendency on all online forums for people to not read the entire thread before commenting. I make the same mistake sometimes. Don't let your experience on this thread dissuade you from sharing your ideas and questions as your build evolves.

[Droo71]

@Droo71,
You appear to understand the insolation numbers and I never worry about a few misplaced kW instead of kWhrs. Any calculations that are critical or involve a large purchase should be checked or reviewed for consistency.
I don't have much to add except to wish you luck as your dream evolves.There is a tendency on all online forums for people to not read the entire thread before commenting. I make the same mistake sometimes. Don't let your experience on this thread dissuade you from sharing your ideas and questions as your build evolves.

Thanks.
I take very little personally - but I do think that ignoring someone's question, and calling them ignorant and confused based on a number that isn't relevant to their question - then refusing to read or acknowledge their modelling or information - well. It says something. And not about me.

I have sent this question around to a lot of places. Three different commercial solar installers did get back to me. All them agreed with my modelling *as long as my load calculation is correct* , so my 100% overhead seems like a decent idea.
One of them sent me some locations in my wiring to look at fuses and breakers that aren't listed in the docs for the panel that I bought, and explained why fuses and why breakers in those spots; he also sent back the math on what i need to charge the battery - and I do need 2 more panels. And its still a better/cheaper idea than going with the L16 battery.