Advice and Expectations

[michaeld]

Hello

I found this forum when I was looking for info on the Classic 150 regulator and I came across the sizing tool and then this forum. Bear in mind before anyone pounces on my granted I haven't had much chance to look around just yet and I will. I've done nothing for the last two weeks 'but' catching up on this best I can.

So far I've only been able to estimate my battery bank for a small system this morning I saw or rather tripped over some systems that were seven and ten kilowatt builds. Those costs made me almost faint. However those were hybrid grid-tie.

If I may pose a question here, I was looking at a four 250 watt panel array using twelve 6 volt lead acid cells that yields 12v at 1,350 amp storage. Is this unrealistic to expect it to work if I only know one hard factor. That is what I consume in billable usage and that has trended around 650 KWH heavy usage to 630 nominal.

If anyone here has an opinion I'd sure like to hear it before I go nuts with it.

Thank you much!
Mike

[Rybren]

Whatever you do, don't spend a penny on anything yet. 

The solar mantra is ready, aim, fire.

Ready involves defining, as accurately as possible, the loads that you would like to run off of your solar system.

Aim involves designing a system - batteries, solar panels to charge the batteries, a charge controller, an inverter, and a myriad of other equipment.

Fire involves building the system and getting it on line.

You currently don't know your loads, so you can't identify what you need in terms of batteries, which in turn means that you don't know what you need in terms of solar panels to charge those batteries.

I suggest that you visit the beginners section of the NAWS forum.  It's about the best place (aside from here) to get you going.
http://forum.solar-electric.com/forumdisplay.php?18-Solar-Beginners-Corner

Good luck.  Read, read, read.  Ask lots of questions.  Don't spend a penny until you've completed the Ready and Aim steps.

One more thing..

If I may pose a question here, I was looking at a four 250 watt panel array using twelve 6 volt lead acid cells that yields 12v at 1,350 amp storage. Is this unrealistic to expect it to work if I only know one hard factor. That is what I consume in billable usage and that has trended around 650 KWH heavy usage to 630 nominal.


Yes, this is unrealistic. 

[TomW]

My real world system is 2,350 watts of solar, 450 AH of tired 24 volt traction battery. At 43 degrees North in the Midwest I manage to run 2 freezers, a fridge, some LED night lites, my network hubs and access points, a cluster of Raspberry Pis and a brace of CAI Webcontrol boards 24/7 and usually can get by without taking the loads off the inverter and on to the grid. Our electric used to be in the 450 to 500 KWH a month and we have it down to about 300 KWH a month. Neither the fridge or the freezers are super efficient but all are "Energy Star" rated. On high production days we heat water in an electric water heater, run the washer, vacuum, power the TV, whatever.  Even run the AC occasionally on bright days.

As pointed out before, learn before you leap. Wrong bits for a system can be expensive over time.  Been there, done that but did not get the T-shirt. 

Tom

I do not have a KWH meter on the RE stuff so cannot give solid figures.

[michaeld]

Thank You for the link Rybren I had been to that site to help choose the battery type and size. I did not notice they also have a discussion forum there as well. I imagine it was due to the deliberation of the cost of the cells? Then to add the costs of the panel an charge regulator it keeps escalating from there.

I'm not even looking at combiner, wire, connectors, shunts, breakers, or any other components that will be required which I'm not even aware I'll be needing. At least after two weeks of shooting-in-the-dark research I was able to find this forum to read. I was aware there is a lot of disinformation on YT as I could tell from some of the builds.

Can you say if it's not possible (given the limited information with regards to the components I chosen so far) or it's simply not possible/feasible given the consumption?

Worry not, I'll not make any purchases until I have an idea if this is do-able and the full cost involved. I'll be able to better look at these forums tonight, but thanks again for the confirmation and link.

Best Regards Rybren,

~~~~~~~~~~~~~
Thank You too TomW,

That is IMO a big success you have with your system and makes further research not seem so futile. I'll throw this in the mix, my biggest power drains do not include electric oven or water heating those are gas fed, although the microwave does eat it up but can be replaced with a lower wattage as this one is overkill.

My next biggest drain is the window type a/c (summer months) then the refrigerator, which I'm currently tracking both with a kill-a-watt meter. Other than that just the lighting and then stereo/flat panel/consumer electronics pc, cellphone chargers so if your running two freezers, and a fridge I guess I should be looking to add to the panel array.

Are you running a 12 or 24 volt bank to get the performance you get? I also forgot to mention I was considering a Samlex 3000W twelve volt converter. At least at this point in my personal learning curve.

Many Thanks for looking in and seeing my post Guys!

Best!

[TomW]

michaeld;

24 volt system. I started at 12 volts but that was a big mistake. Had to replace everything eventually to get up to 24 volts. Frankly, I wish I had gone to 48 but at the time 48 volt was more uncommon and pricey. I think that is not so now. Midnights controllers can feed 12,24,48 and some do 36 volts I think. Once you get up into serious system land, say 2500 watt inverter you get to a point where 12 volts just won't be practical on cabling to feed the inverter.

Best of luck.

Tom

[Rybren]

As Tom alluded to, a 12V system is not the way to go on the type of system that you will likely require.  A very roughguide is that 12V is good for inverters up to 1000W;  24V for up to 2000-2500ishW; and 48V for anything larger.

The size of your battery bank is determined by your loads and days of autonomy(days before you have to fire up a generator).  The size of your PV array is determined by the size of your battery bank.  The inverter output is determined by the maximum continuous required output and the size of your biggest load (think big surge on startup of motors and compressors)

Your proposed battery bank would be six parallel strings of batteries.  It would be virtually impossible to charge them equally and you'd likely kill them.  At a size of 1,350AH, you'd want to be able to pump ~135AH into that bank.  A 1000W isn't going to cut the mustard for you.

Please visit the link that I provided to NAWS.  The forum is very active and the folks there will help you design something that will meet your needs.

Cheers,

Jerry

[vtmaps]

I was looking at a four 250 watt panel array using twelve 6 volt lead acid cells that yields 12v at 1,350 amp storage.

Jerry was too gentle about running 6 parallel strings of batteries... it's much worse than he said.  You want a single string of batteries at whatever amphour capacity and voltage will support your needs.

You should realize that 1350 ah at 12 volts is the same as 675 ah at 24 volts is the same as 337.5 ah at 48 volts.

First step is determine your loads.  Second step is pick a battery and system voltage that can handle the load.  Third step is buy enough solar array and electronics to charge the battery. 

--vtMaps

[michaeld]

Well I must say in just a few hours here it's been quite the eye opener but at least I've seen the light so to speak. My curve so far has been evaluating the practicality of gas/propane generators a month or so ago. Lugging petrol or storing bulk isn't much an interest.

I can't say for anyone else's but likely it's the Harbor Freight small load lo-cost kits that catches the interest initially then I became aware of the 15 and 30 amp TriStar regulators and google didn't offer up much from there. It was only this morning I became aware of the Outback 80 amp and subsequently the 96 amp Classic 150 from what little time I've had today now I know that Sunny Boy makes a reputable 6000W off-grid converter.

It seems like the converter is the component most prone to failure from some instructional videos but I'm not even sure that is an accurate opinion. The bank I had selected was a single string of two 6 Volt 225 amp LA cells in series by four 12 Volt (equiv) in parallel to get that 1,350 rating.

From your estimate of a 135 amp charge rate, can I safely assume that ten percent overhead to hold true now that I realize I will need to go with a higher voltage converter supply? At the same time it occurs to me that even if the load didn't exceed the ratings of the bank, in this example it still exceeds the ratings of the chg/controller. But would it be wise to use it as a rule with the larger battery bank?   

If there are any replies I will be sure to read them but I may not trouble you with more beginner questions for a day or two. I need to step back take a break let this all sink in. I already know that if I go with a higher voltage supply, I am going to switch from LA type to AGM type. Those were I believe just 20 more per cell if I remember? Although in the past I haven't had much luck with closed cells but at least I won't have to be as cautious about hydrogen build up.

I'm going to watch some jeopardy and do some reading. I do value your comments and suggestions. I'll pop up again after I study a bigger bank/converter supply. Many Thanks!

Mike 

~~~~~~~~

Hello vtmaps! it wouldn't let me post my reply until I read your post. Thank you for the relationship of amps to Xvolts,
this info may be common or basic ohms law but it wasn't quite as evident to me right at the moment. But this pause to read your comment made me think of one question not so much technical as it is to common sense to those experienced with PV systems either designers or owners.

In my limited experience with panels (10 years ago) with the newer cells/panels would it be prudent to expect 90 percent or better chg output over a 6 hour period on a good day that is? and roughly how much trickle chg percentage should you expect over the 2 hours at twilight and dawn or would those hours be negligible?

Thanks Mike

[michaeld]

That was such a wordy reply I didn't notice I had missed stating the reason I'm looking into off-grid heavy load. So for the last three summers running the line xfmr just up the street (between me and the sub-station) has popped from the heat as it's running at a peak load from the neighborhood. Now their fast as can be getting a new one in, it's back on in the morning. A-OK there.

It's the net hurricane Sandy that gnaws at me trying to get to sleep at night. The last thing I need to hear is one more 'I Told You So'.

[vtmaps]

In my limited experience with panels (10 years ago) with the newer cells/panels would it be prudent to expect 90 percent or better chg output over a 6 hour period on a good day that is? and roughly how much trickle chg percentage should you expect over the 2 hours at twilight and dawn or would those hours be negligible?

Figure out how many "equivalent sun hours" your location has (you haven't told us your location).  That means, for example, that even if you have 14 hours of daylight, it works out to perhaps the equivalent of 5 hours of noontime sun.

equiv sun hours  X  array wattage  X  75%  =  the energy (in wattHours) that your array produces each (sunny) day.  It will vary with the seasons in most locations.

The most important thing for you now is to calculate your loads so that a system can be designed.  And abandon all thoughts of designing the system with either 12 volts or parallel batteries. 

--vtMaps

[Vic]

Hi michaeld,

Regarding the amount of solar energy that you might expect for your location (in the USA,  am assuming),  here is a link to the NREL PVwatts2 solar calculator:

http://pvwatts.nrel.gov/pvwatts.php

And,  CONSERVATION is the first order of business,  after you have a good handle on the loads that you now have.

Also,  systems connected to the Grid can work well,  but many of those systems produce NO POWER when the Grid is out.  There is an SMA INVERTER which has a -TL suffix that allows limited use of solar power from your PV modules even when the Grid is out -- but only when the sun is shining brightly onto the PV modules.  This could allow running a refer/freezer,  TV,  etc during the day,  but one would need to coast through the night,  and during bad weather.

Many people could do quite well with a smallish Inver-generator and perhaps 20 or so gallons of stored fuel,  during "disasters".  Generators,  like the Honda EU2000is,  can run most essentials in many homes,  while sipping fuel,  and making little acoustic noise.

Just something to think about.   And,  yes,  please study much,  before buying anything.

The wind-sun site that was mentioned previously,  is a great resource  when trying to design a system.

More later,  have fun,  good luck.    Vic

[michaeld]

I meant to also state my latitude last time but I'm at 40 degrees north but instead of the mid-west I'm closer to the eastern seaboard in Roxbury NJ. Thank you for the time plots, I'll need that info soon enough in other considerations.

For right now I need to clear my mind on this last bank plan while I'm getting it wrapped around my load requirements. Basically from what I can tell my biggest worry is a load created by a 25K btu window a/c. That runs 24/7 only in the summer months with optimal sunlight. I would venture to say at best with lighting overall another 200 watts intermittent only at twilight, refrigeration ~ 4-500 Watts 24 hour period, another 125 Watts max for consumer electronics.

I could be shocked with my estimates as I haven't measured every appliance. The microwave is a whole another issue altogether. With as little use as it see's it's a good possibility it may not survive a transition when it comes. Checking the price of a 6048W SMA inverter it more than quadrupled the price of a 3Kw one, but it looks to be heavy duty. I was considering a backup to the Samlex.

If anyone is interested in checking my math, at the following link I was converting KwH to Kw just to get a rough estimate. If I take the 650kwh usage (then take 24hrs * a 30 day cycle = 720 hours) this calculator tells me I use 0.90277777778 per hour, so essentially in a 24 hour period I use 21.67 kw or at the heart of the issue is this figure even relevant to the drain on the bank?

Once I get a footing on either the solar array or the cell bank I should be able to figure out the unknown value of the other. I don't know I may have even confused you guys at this point. If your hanging in there with me God Bless and Thanks!

Mike

http://www.rapidtables.com/calc/electric/kWh_to_kW_Calculator.htm

~~~~~~

Excellent advice Vic! I may have to re-visit the little Honda option if that is what I'll need to do for supplemental charging.

Thank You Sir!

[Rybren]

Michael,

Your proposed system will not be small; it will be very large and you must get it right!

Grab that Kill-A-Watt meter and measure everything that you plan on using.  Measure each item over an extended period of time (say 3 or 4 days) to ensure that your readings are good.  You should then have a good grip on your load baseline.

I'm a tad confused about your proposed battery bank and it makes me think that you might also be confused.  You intitially stated that you wanted a 12V system comprised of 12 6V batteries for a capacity of 1,350AH.  That would be 6 parallel strings of 2 batteries.  Each battery would have a capacity of 225AH (6 x 225 = 1,350)

In a later post you said that The bank I had selected was a single string of two 6 Volt 225 amp LA cells in series by four 12 Volt (equiv) in parallel to get that 1,350 rating.  Four parallel strings (still too many)  would be 225 x 4 = 900AH not 1,350.

Remember, voltage adds in series, but the AH remains the same: 6V @ 225AH + 6V @225AH = 12V @ 225AH.
AH adds in parallel, but the voltage remains the same: 12V @ 225AH + 12V @ 225AH + 12V @ 225AH + 12V @ 225AH = 12V @ 900AH

[michaeld]

Yes it is quickly catching up to me! usually I over engineer projects! This is the simple but under rated bank I came up with. I still may use it and choose 12 volt cells to get to a 24 volt supply unless I'm advised of the method used to obtain a 48 volt supply. I'm starting to see that two chains of this circuit would get me that penitential but if thats the case it means 24 cells and twice the footprint. Maybe a shelf of some kind would support that kind of weight? Sorry for my crude diagram not very good at pc paint.

- 6 + ---- - 6 + (2x 225=450a)
|                  |
- 6 + ---- - 6 +
|                  |
- 6 + ---- - 6 +
|                  |
- 6 + ---- - 6 +
|                  |
- 6 + ---- - 6 +
|                  |
- 6 + ---- - 6 +
|                  |
|                  |
(2x6=12vdc)

Best,
Mike

[michaeld]

Obviously I'm overloaded mathematically today I should have written 2x 6 volts at 225 amps at the top. The coverage calculator Vic linked to gave some better than expected results.