Solar wiring questions (newb)

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frohickysmolder
frohickysmolder Registered Users Posts: 11
Hey I am piecing together my solar system. I started with (no knowledge and) 4 Sharp 240 watt panels. (Poly, about 38 volt.) I decided to wire them in parallel to keep the voltage the same, and bought a Morningstar MPPT-60 to cover the higher amperage. I have chosen to wire that to 5 110ah AMG batteries (i would have gotten more but i figure i could run a simple grid tie if my panels put out too much, and batteries are quite $$ as you probably know), and invert it with a 1000 watt Xantrex inverter.

I have not been able to figure out what size wire I should be using. (my research indicates 8 or 10 AWG but i dont know) I can probably get very short distances between all the equipment except the panels which will need probably 20-40 feet to get into the house. I'm not sure how to figure out wiring tho I have looked into it.

I am no electrician or carpenter but I feel pretty comfortable hooking up everything when i get around to it, tho this is my prime concern. I think I have compatible equipment, but please inform me if i dont. I know this is my first post here, but if anyone could help with proper wire sizing, perhaps it could be of value to your board. If this answer is elsewhere I'd appreciate it if you would toss me a hint.

I guess a follow up question is after reading the manuals for the equipment i have, they mention providing a set of breakers in between batteries and inverter, and in between panels and charge controller. I would assume you all agree this is necessary?

Sorry if I sound naive or intrusive on your board, but I'm looking to do things effectively and have a hang up on the wiring part. I don't know who else to ask, short of a proprietor at an electrical supply who would likely have some input. How hard is the actual wiring? Should I just find a rogue electrician and pay him a couple hours labor to do it up once I have the supplies? Or since I have made it this far should I just get it done myself.
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  • KeithWHare
    KeithWHare Solar Expert Posts: 140 ✭✭✭
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    Re: Solar wiring questions (newb)

    A very basic question is what sort of loads are you hoping to support with your system?
    Hey I am piecing together my solar system. I started with (no knowledge and) 4 Sharp 240 watt panels. (Poly, about 38 volt.) I decided to wire them in parallel to keep the voltage the same, and bought a Morningstar MPPT-60 to cover the higher amperage. I have chosen to wire that to 5 110ah AMG batteries (i would have gotten more but i figure i could run a simple grid tie if my panels put out too much, and batteries are quite $$ as you probably know), and invert it with a 1000 watt Xantrex inverter.

    How are you planning on configuring the batteries and what are the rest of the specifications on the batteries?

    Five batteries is an odd number. Are these 12 volt batteries that you are hoping to wire in parallel? Please take a careful look at the battery FAQ: http://www.windsun.com/Batteries/Battery_FAQ.htm

    Oh, and the phrase "simple grid tie" is an oxymoron. For starters, you are describing a "grid interactive" system -- a "grid tie" system does not have batteries. When you link to the grid, things are not "simple" and you certainly will not do it with a 1000 watt Xantrex inverter.
    I have not been able to figure out what size wire I should be using. (my research indicates 8 or 10 AWG but i dont know) I can probably get very short distances between all the equipment except the panels which will need probably 20-40 feet to get into the house. I'm not sure how to figure out wiring tho I have looked into it.

    For low voltage systems, voltage drop is the driving factor in choosing the correct wire size. There is a wire sizing spreadsheet around here someplace. I like the wire sizing calculations at http://www.electrician2.com/calculators/vd_calculator.html. The important thing to remember is that the appropriate wire sizes depend on how everything else is configured.
    I am no electrician or carpenter but I feel pretty comfortable hooking up everything when i get around to it, tho this is my prime concern. I think I have compatible equipment, but please inform me if i dont. I know this is my first post here, but if anyone could help with proper wire sizing, perhaps it could be of value to your board. If this answer is elsewhere I'd appreciate it if you would toss me a hint.

    Once you get everything carefully designed, the hookup is pretty easy.
    I guess a follow up question is after reading the manuals for the equipment i have, they mention providing a set of breakers in between batteries and inverter, and in between panels and charge controller. I would assume you all agree this is necessary?

    The goal of the breakers & fuses is to protect the wires. You do not want a short circuit to cause a wire to heat up and melt. So yes, breakers and fuses are necessary in a number of places.
    Sorry if I sound naive or intrusive on your board, but I'm looking to do things effectively and have a hang up on the wiring part. I don't know who else to ask, short of a proprietor at an electrical supply who would likely have some input. How hard is the actual wiring? Should I just find a rogue electrician and pay him a couple hours labor to do it up once I have the supplies? Or since I have made it this far should I just get it done myself.

    Electricians who are used to working with 120 & 240 volt AC think of wire sizes in terms of ampacity. With 12, 24, or 48 volt, reducing voltage drop is the bigger factor in choosing wire sizes. If you don't understand what and why you are doing something, working with an electrician who doesn't understand what and why will result in a non-optimal system.

    I highly recommend that you spend some time carefully understanding what you are hoping to accomplish and how you can use the pieces you have to accomplish your goals before you start hooking things up.

    Keith
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Solar wiring questions (newb)

    Welcome to the forum.
    It's cruelty time! :D
    I started with (no knowledge and) 4 Sharp 240 watt panels. (Poly, about 38 volt.) I decided to wire them in parallel to keep the voltage the same, and bought a Morningstar MPPT-60 to cover the higher amperage.

    The only part of that which makes sense is "I started with no knowledge". That's common ground to us all! :p
    Your panels will have a lot more specs that "about 38 Volt" which is probably the Voc and means the Vmp is around 30-ish.
    "I decided to wire them in parallel to keep the Voltage the same". The same as what? You've got an MPPT charge controller, make use of it! You've got 20 to 40 feet (pretty big difference) between the array and the controller? Higher Voltage helps overcome wiring resistance.
    The next bit; five 110 Amp hour batteries. What system Voltage are you trying to run? My guess is that is five 110 Amp hour 12 Volt batteries and you're wiring them in parallel. That is a mistake you should not make. Five parallel connections of batteries will be trouble. The Xantrex 1kW inverter confirms my 12 Volt suspicions.

    As Keith said, you can't just take any extra power from an off-grid system and feed it to the grid. It is far more complicated than that.

    To be blunt, at this point you don't have the understanding of the basics to continue on. No point in worrying about wire sizes or fuses yet. So let's get helpful!

    Four 240 Watt panels on an MPPT controller. What can you get from it?
    960 Watt array. @ 77% efficiency (typical) on a 12 Volt system: 61.6 Amps of peak current. That will "max out" your charge controller. It would be able to charge 600 Amp hours of 12 Volt battery, enough for up to 3kW hours AC. Quite a bit of power.
    On a 24 Volt system you'd have bout 30 Amps of peak current. No problem handling that. 300 Amp hour 24 Volt battery bank, and the end power amount will be the same with a slight improvement in efficiency. Less current = less power going to heat instead of work.
    With a 24 Volt system you would put two parallel strings of two of those panels in series. Easy connection, no fusing on the panels, good conversion efficiency, low power loss to Voltage drop in the wires. You could do the same for 12 Volt, but with a slight drop in conversion efficiency. On the whole, a 24 Volt system would work better with those panels.

    But not with those batteries. In fact, those batteries are probably all wrong. If you want the 600 Amp hours 12 Volt size you are better off with using larger capacity 6 Volt batteries in series rather than paralleling a lot of 12 Volt units.

    What else you can expect from that array is about a minimum of 2 kW hours AC per day. That would work well with a 25% maximum DOD on the batteries.

    On the whole you have the start of a good system, even if you skipped the part of figuring out how much power you need before you try to supply it. :roll:
    But I think the batteries are a mistake (AGM's by any chance?) and so is the choice of a 12 Volt system (change the inverter).
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Solar wiring questions (newb)

    "........but i figure i could run a simple grid tie if my panels put out too much,......."

    DANGER!!!

    as to connecting that inverter to the grid the guys have underscored this a bit too much. do not do this with an inverter not meant for grid tie. at the minimum sparks will fly and your inverter will be toast. the worst case is you would be killed either by electrocution or by a possible resulting fire.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
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    Re: Solar wiring questions (newb)
    niel wrote: »
    "........but i figure i could run a simple grid tie if my panels put out too much,......."

    DANGER!!!

    as to connecting that inverter to the grid the guys have underscored this a bit too much. do not do this with an inverter not meant for grid tie. at the minimum sparks will fly and your inverter will be toast. the worst case is you would be killed either by electrocution or by a possible resulting fire.

    And just to add to the caution:
    Do not try to add a "simple" grid tie using one of the import "grid-tie inverters" which plug into an AC wall outlet. These are not safe and are also not legal in the US and most other countries!
    SMA SB 3000, old BP panels.
  • frohickysmolder
    frohickysmolder Registered Users Posts: 11
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    Re: Solar wiring questions (newb)

    Thanks for the inputs they are appreciated.

    First, no I was not planning to hook that inverter up to the grid. They sell separate units designed for that. If they are not safe then I would appreciate a link if you know of any that talk about it. The only reservation i heard was with reference to "islanding" and as far as i know this was taken care of by a automatic cut off when power from the grid was removed. I was under the impression that they are fine for small application, i have seen videos and read a few things, but you are the experts so inform me.

    Second, i designed the system trying to make it fit without breaking the bank. that is how i designed the whole system really. I don't care about meeting my needs but only as an insurance against power outage and as a intellectual and DIY project to increase my sustainability. So i'm not awfully concerned with designing the system in the usually prescribed order.

    Third, So it seems you are all saying that i have done somewhat ok, but I am not quite there and have maybe made some mistakes already. how would you go about correcting these mistakes without breaking the bank. I'd rather not have to put any of the equipment up for sale, especially the heavy batteries. So the batteries, yes I was planning to wire my 12 volt AGM batteries in parallel for that inverter. I don't understand why 5 is an odd number, i just bought how many seemed practical and I thought that 500 ah would be sufficient to run some devices. I figured if my solar panels produced too much for them I could take a panel and remove it from the system and hook it up to my aforementioned grid tie inverter. I didn't imagine that the batteries would be the problem, except i have read that you shouldnt add or subtract batteries once the batteries begin to age together. It seems maybe replacing the inverter is a better cheaper idea? Maybe someone can elaborate on what the defficiency i have created is.

    Fourth, good ok will use breakers at the two points i specified.

    Fifth. So I really appreciate all of your input. I know I said I have no knowledge, and perhaps was a little silly to try and design my system by purchasing bits and pieces as I thought i gained understanding, but in the end I am not an idiot and hope you will help me prove it! lol. no im not gonna blow up the house plugging a regular inverter into the wall, perhaps I have been fed misinformation about the practicality and safety of what are termed "plug and play" grid tie inverters. I had seen evidence of them working on the internet, but I know that isn't the end all of the discussion. Most house fires begin after the cameras went off.....

    I will re-read what you have all wrote and hope you can offer me some additional information. I hope you can inform me how you would correct this system. If i have still left out any vital information please let me know what that was and I will tell you. I do not want really expensive paper weights, or to have to spend the money involving a solar company at this juncture.

    Thanks again

    Ok so on edit.

    Cariboocoot. Very helpful. But oh no so you are saying my batteries are wrong. Now what the heck am i supposed to do? If you could get very specific to me as to why they are wrong perhaps I could see how to solve this situation. I understand the words and your ************, but perhaps in better understanding the why I can see a way to fix this.

    I think originally when I was going to wire the panels in parallel it was trying to avoid a combiner box. I figured making the panels in 1 array as opposed to 2 (if this is improper terminology please excuse me) i could avoid a combiner box. I think since i am going to have the combiner box your point makes perfect sense and is better than cutting corners...

    So my problems boil down to your issue with the batteries. What can I do??
  • frohickysmolder
    frohickysmolder Registered Users Posts: 11
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    Re: Solar wiring questions (newb)

    And as for my minimum expected of the system. I believe that is high heat generating lighting. This way I can generate heat and light using high wattage to double the productivity of the system in cold weather. If you have sen Paul Wheatons videos on reducing your energy bill you will see that a simple 75 watt light can be a very effective space heater. Using a couple higher powered lights can easily make a room liveable even in the dead of winter. These run much lower wattage than a space heater which my system wouldn't run very well IMO.

    The other usage in a power outage situation will be an occasional refrigerator load and the charging of smaller batteries including lighting and communications uses.


    Two side notes/questions

    One. When a panel is left in the sun unconnected to any equipment where does that power go? does it damage the panel? I have been tentative to work on putting up the panels until I have a usage ready.

    Two. Have any of you tried using an alternator with a bike to charge up the same batteries connected to a solar array? Does it make more sense to separate the batteries for different charging mediums?
  • KeithWHare
    KeithWHare Solar Expert Posts: 140 ✭✭✭
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    Re: Solar wiring questions (newb)
    ...
    So the batteries, yes I was planning to wire my 12 volt AGM batteries in parallel for that inverter. I don't understand why 5 is an odd number, i just bought how many seemed practical and I thought that 500 ah would be sufficient to run some devices. I figured if my solar panels produced too much for them I could take a panel and remove it from the system and hook it up to my aforementioned grid tie inverter. I didn't imagine that the batteries would be the problem, except i have read that you shouldnt add or subtract batteries once the batteries begin to age together. It seems maybe replacing the inverter is a better cheaper idea? Maybe someone can elaborate on what the defficiency i have created is.
    ...

    The issue with wiring five batteries in parallel is that it is highly likely that the resistance of the battery and the wires will not be exactly equal across all connections. Because of this inequality, the battery with slightly higher resistance will not get charged quite as well and so will degrade more quickly and drag down the performance of the rest of the battery bank. The usual recommendation is to use no more than three battery strings in parallel.

    The issue with using 12 volts instead of 24 or 48 volts is amps versus watts. Since Watts = Volts x Amps, If you are drawing 480 watts from a 12 volt system, you need to draw 40 amps. With a 24 volt system it would be 20 amps while a 48 volt system would be 10 amps.

    40 amps will require a much larger wire than 10 amps. For example, 40 amps at 12 volts have a 2% voltage drop in 20 feet of #10 wire, while 10 amps at 48 volts have a 2% voltage drop in 50 feet of #12 wire.

    Because of these two considerations, there would be some benefits in using 4 batteries in series for a 48 volt system or two strings of two batteries for a 24 volt system.

    Keith
  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
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    Re: Solar wiring questions (newb)
    If they are not safe then I would appreciate a link if you know of any that talk about it. The only reservation i heard was with reference to "islanding" and as far as i know this was taken care of by a automatic cut off when power from the grid was removed.

    Yes, and UL listed devices do just that. Chinese GT inverters might not. As a quick way to tell - if it has a plug on it it's not UL listed. Grid tie requires a hard connection.
    Second, i designed the system trying to make it fit without breaking the bank. that is how i designed the whole system really. I don't care about meeting my needs but only as an insurance against power outage and as a intellectual and DIY project to increase my sustainability. So i'm not awfully concerned with designing the system in the usually prescribed order.

    No problem, but I would strongly recommend spending the big bucks on the important stuff - wire (it's expensive) circuit protection and mounting structures. Those are the things that will keep you from getting hurt (starting fires etc.) Go smaller on the system if you have to but DO NOT skimp on the above.
    So the batteries, yes I was planning to wire my 12 volt AGM batteries in parallel for that inverter. I don't understand why 5 is an odd number, i just bought how many seemed practical and I thought that 500 ah would be sufficient to run some devices.

    It is odd because it is VERY common for people to go to 24 or 48 volts once they understand solar a little better - and with 4 batteries you can do 12, 24 or 48 volts.
    I figured if my solar panels produced too much for them I could take a panel and remove it from the system and hook it up to my aforementioned grid tie inverter.

    No listed GT inverter will work at 12 volts. Also switching a panel from one load to another is probably not something you want to bite off at your stage. I'd recommend a standard charge controller.
    I didn't imagine that the batteries would be the problem, except i have read that you shouldnt add or subtract batteries once the batteries begin to age together. It seems maybe replacing the inverter is a better cheaper idea? Maybe someone can elaborate on what the defficiency i have created is.

    Paralleled batteries don't work well. Seriesed cells work a lot better (i.e. higher voltages/lower amp hour battery banks.)
    I think originally when I was going to wire the panels in parallel it was trying to avoid a combiner box. I figured making the panels in 1 array as opposed to 2 (if this is improper terminology please excuse me) i could avoid a combiner box. I think since i am going to have the combiner box your point makes perfect sense and is better than cutting corners...

    You've got that backwards. Parallel connections require combining; series (higher voltages) do not.
  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
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    Re: Solar wiring questions (newb)
    And as for my minimum expected of the system. I believe that is high heat generating lighting. This way I can generate heat and light using high wattage to double the productivity of the system in cold weather. If you have sen Paul Wheatons videos on reducing your energy bill you will see that a simple 75 watt light can be a very effective space heater. Using a couple higher powered lights can easily make a room liveable even in the dead of winter. These run much lower wattage than a space heater which my system wouldn't run very well IMO.

    A 75 watt light bulb works as well as a 75 watt heater. Same heat output (tiny.)

    Unfortunately resistance heating is the worst possible application for solar, and only works in very specific applications (i.e. guy in Phoenix who wants to heat a small area during the day.)
    The other usage in a power outage situation will be an occasional refrigerator load and the charging of smaller batteries including lighting and communications uses.

    Lighting (CFL or LED) and communications are good applications for a system like this one.
    One. When a panel is left in the sun unconnected to any equipment where does that power go? does it damage the panel? I have been tentative to work on putting up the panels until I have a usage ready

    Nope. Voltage goes to Voc and just sits there. No damage.
    Two. Have any of you tried using an alternator with a bike to charge up the same batteries connected to a solar array? Does it make more sense to separate the batteries for different charging mediums?

    Sure, that works. But you're going to get at _most_ around 100 watts. (Don't bother separating the batteries.)
  • CATraveler
    CATraveler Solar Expert Posts: 98 ✭✭✭✭
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    Re: Solar wiring questions (newb)

    With those batteries you could wire them in parallel in a balanced manner but I'd go for 24 or 48V using 4 batteries. You could maintain one battery for a year and rotate the batteries every year so that at 5 years every battery would have 4 years of service and 1 year maintained. Will give you longer life as you'll be good until the second battery dies. You could also buy another battery and use the 6 for a 24V system.

    Maybe I missed what type of battery but hopefully they are deep cycle.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: Solar wiring questions (newb)

    A watt is a watt, is a watt! A watt/hour contains Contains ~3.4 BTUs (if my math is right) it doesn't matter if that heat comes from a light bulb, or waste heat in a Tv set,,as you consume power, it all comes out as heat in the same rate! The only possible benefit form " heating with light bulbs" might,, read might be a ir heat lamp MIGHT. Make you feel warmer, bu in the net, the temp in the room will e the same if it comes from a Ir bulb, or a conventional.

    My suggestion, with all due respect, is stop watching " get something for nothing" videos done by people who either have a snake oil product to sell or go plain don't know wha they are talking about. As has been said before, resistance electric heating is a loser for pV, as there are way better ways to use PV and,, to heat. You have however come to the right place, there some very smart folks here (engineers, solar designers, PV designers etc) who actully know what they are talking about. Many have forgotten more about the subject than most of us will know.

    Leave your preconceived notions at the door, read all you can, and sooyou will be on the right track,, just avoid the " ready, fire, aim syndrome!

    Welcome and keep in touch,

    Tony
  • frohickysmolder
    frohickysmolder Registered Users Posts: 11
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    Re: Solar wiring questions (newb)

    OK so thanks for the idea about the spare battery. That may be the way I go. But then it looks like I'm going to have to exchange out my inverter because the one I selected will not accommodate a 24 volt system. This is most unfortunate. Any ways you suggest I do this I I rid myself of the packaging. Will I get close to my money back if I just place it on ebay or are there solar resale boards or anything?

    The comment about videos on youtube I cant really agree with. The problem you are correct about. I find that when most people make a video on youtube it is their first attempt at something. This is a sort of get rich quick scheme and it does tend to reproduce false info and poor technique. (In my situation that is far from where I got most of my information. If i did i would still be gluiing together solar cells, because its "so easy". I thank everyone here for helping me, but that disadvantage that youtube creates could be corrected if more of these masters would take time to produce good material on youtube. Of course then you are a free working corporate slave of google and thats a whole other story.

    Now you say a watt is a watt, and obviously that is so. But the usage of a watt in different ways has different attributes. No body would think to light their house with a space heater, because a space heater has a limited function. It creates hot air and blows it through a fan to circulate it. Furthermore a watt (and I am only guessing) can be concentrated down from a light in a more laserlike form. This would concentrate that watt further and give a specific heat to a smaller location. This is a similar or same reason why we can light a fire with a magnifying glass. So using a wattage in light I believe to be more functional. The heat will be concentrated into the area of the light, as well as not being only a heating element.

    If you are going to say there are inefficiencies in different types of appliances then of course I will have to agree with you. Maybe you would say that a heater and a light is more efficient than using the same light for both heating and light. I don't know. But I have used lights that are 1/3 the wattage of a space heater and seem to give a very similar effect.

    I'm not a fan of CFL's but I'll keep that in mind. To me they are pollutants and not nearly as effective as incandescent lighting. They also dont create much heat. flicker, and don't have the longevity of the traditional light.

    [snip--I think the cut and paste from Notepad got a bit out of hand--I think I edited to what was intended. -Bill B.]
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Solar wiring questions (newb)

    :confused:
    I think I'll just go back inside my cave and wait for Spring.
  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
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    Re: Solar wiring questions (newb)
    If you are going to say there are inefficiencies in different types of appliances then of course I will have to agree with you. Maybe you would say that a heater and a light is more efficient than using the same light for both heating and light. I don't know. But I have used lights that are 1/3 the wattage of a space heater and seem to give a very similar effect.

    If you can use the light, great. But again, resistance heat just doesn't work that well with solar - and using incandescents doesn't create more heat than a heater would.
    I'm not a fan of CFL's but I'll keep that in mind. To me they are pollutants and not nearly as effective as incandescent lighting. They also dont create much heat. flicker, and don't have the longevity of the traditional light.

    So use LED's. CFL's last a lot longer than incandescents, and LED's last even longer.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: Solar wiring questions (newb)

    I repeat, a watt, is a watt, is a watt! Plug in a 100 watt light bulb, or a 100 watt Tv and they produce the same heat into the room! The only potential exception to the rule might be in the case of a very high efficincy heat pump system than can, theoretically produce more BTUs into the room than it takes to run it. All loads are resistive, and "doing work" being lighting a light bulb or driving a drill creates heat.

    Like I said, spend some time doing some real research, here and elsewhere, and begin to understand the basics. As for CFLs, you are a products of a lot of misinformation. True, CFLs do have minute amounts of mercury, (which is 100% recylable and many major retailers including Home Depot etc) but the energy saved is enormous, and more importantly, they actually reduce the amount of mercury emitted into the atmosphere by a significant factor by reducing the emissions from generating stations. CFLS also reduce power consumption in a number of other ways. For example, in a air conditioned environment, every watt of light bulb heat has to be removed from the A/C environment. (remember the watt is a watt conversation?) So a typical CFL might reduce power consumption by ~75%,(on a per lumen basis) reducing A/C loading.

    all that said, LEDs are the wave of the future. I am now writing this with the light of a 4 watt LED reading light, that is way better than the high intensity halogen it replaced (before the CFL), at about 1/20 the power consumption.

    Tony
  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
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    Re: Solar wiring questions (newb)
    OK so thanks for the idea about the spare battery. That may be the way I go. But then it looks like I'm going to have to exchange out my inverter because the one I selected will not accommodate a 24 volt system. This is most unfortunate. Any ways you suggest I do this I I rid myself of the packaging. Will I get close to my money back if I just place it on ebay or are there solar resale boards or anything?

    Yea--That is why we try to get people to plan out their system before making purchases--We can help make what you have work--But sometimes the drawbacks are a bit much to deal with (costs, large numbers of parallel battery strings, etc.).

    We do allow people to post personal items for sale on the forum (no commercial sales unless pre-approved--And please conduct conversations between buyer/seller with PM's or Emails (recommend you don't post personal email addresses to avoid spammers).
    For Sale Thread
    The comment about videos on youtube I cant really agree with. The problem you are correct about. I find that when most people make a video on youtube it is their first attempt at something. This is a sort of get rich quick scheme and it does tend to reproduce false info and poor technique. (In my situation that is far from where I got most of my information. If i did i would still be gluiing together solar cells, because its "so easy". I thank everyone here for helping me, but that disadvantage that youtube creates could be corrected if more of these masters would take time to produce good material on youtube. Of course then you are a free working corporate slave of google and thats a whole other story.

    Because of the differences between a system with a 100 watt solar panel vs a 5kW system, Grid Tied/Off Grid/etc. ... So far, it has been (hopefully) more helpful to write "personal" replies in the threads... That is why we try to ask poster how much power do you need, 1 season/4 season, off grid, emergency power, save money, etc...

    Once you have been through the design process "once"--Then the rest of the PV World starts to make a bit more sense.
    Now you say a watt is a watt, and obviously that is so. But the usage of a watt in different ways has different attributes. No body would think to light their house with a space heater, because a space heater has a limited function. It creates hot air and blows it through a fan to circulate it. Furthermore a watt (and I am only guessing) can be concentrated down from a light in a more laserlike form. This would concentrate that watt further and give a specific heat to a smaller location. This is a similar or same reason why we can light a fire with a magnifying glass. So using a wattage in light I believe to be more functional. The heat will be concentrated into the area of the light, as well as not being only a heating element.

    In general, most of us here are "cheap". :p

    Off Grid solar power costs around $1 to $2+ per kWH hour--Or about 10x the cost of grid power in North America. So, electric "heating" tends to be very eexpensive when done with solar PV power.

    Certainly, "free" heat from a Refrigerator is great in a cabin. And I agree that a 150 Watt TV heats up our bedroom pretty nicely (we insulated, double pane windows, CFL and now a few LED lamps, etc. for our 70 year old home).

    But--It comes at a price... The rough price being that a 150 Watt of "free heat" from a filament lamp costs about the same as a 1,500 watt electric heater on grid power.

    If that is worth it too you (hauling propane/oil for heating, no wood lots nearby, etc.)--Then we are more than happy to help size your system for those loads.

    On the other hand, using solar thermal panels (and extensive home insulation) can be better, more cost effective options.

    And there are "heat pumps" (both mini-spit A/C heat pump systems, and even heat pump water heaters) that generate about 2x the amount of heat (even in fairly cool weather) vs using pure "resistance" heaters (the new mini-splits have even made off grid A/C and electric heating very reasonable for many people with only solar PV power these days).
    If you are going to say there are inefficiencies in different types of appliances then of course I will have to agree with you. Maybe you would say that a heater and a light is more efficient than using the same light for both heating and light. I don't know. But I have used lights that are 1/3 the wattage of a space heater and seem to give a very similar effect.

    In the end, if you need "a little space heating", then a filament bulb may be the answer for you. If you need more--Then there are usually better options available (less costly).
    I'm not a fan of CFL's but I'll keep that in mind. To me they are pollutants and not nearly as effective as incandescent lighting. They also don't create much heat. flicker, and don't have the longevity of the traditional light.

    I agree--And certainly my wife does too... Until we saw how much money we saved on Grid Power by going with conservation--She has said OK to CFLs. Also, we have some warm days in Summer and the CFL/LED bulbs keep the house way cooler these days vs the old filament type bulbs.

    If I needed filament bulbs (and I still use a few), I like the Halogen type. You can get regular "screw base bulbs" with Halogen "capsules" inside. Halogen at full voltage are still relatively efficient, and they look so much better when dimmed (I will never get another "dimmable" CFL lamp for that purpose--And the LED "white" is still a bit off for me--and highly variable between brands and even date codes).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • frohickysmolder
    frohickysmolder Registered Users Posts: 11
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    Re: Solar wiring questions (newb)

    Perhaps I didn't adequately explain my expectations. My expectations are primarily that I will have electricity when my grid goes down. That is the goal I wishd to accomplish. After that the loads I mentioned are only based on what I have speculated. I come at this project like a 'survivalist' or 'prepper' all other benefits, like a hedge against rising kwh cost is extra. I want to charge radio batteries and perhaps run the aforementioned lights or fridge. I have also heard that an ice maker is a better method in outtage because its smaller than keeping a whole fridge cold. The ice placed in a cooler is better. I plan to figure these things out when I have a base system.

    As for the CFL's in my experience they dont last as long as incandescents nor are they nearly as functional. Can someone explain to me how a watt is a watt is a watt if the differences in the lights clearly show different wattages with "comparable" functions?

    Next I have to wonder now that since you all put my inverter to rest, any suggestions on a reliable inverter for the system I have described? I think we decided that the 4 battery system at 24 volts was accepatble and I would rotate my extra battery. As a prepper i like the idea of adding life to the battery. In an outtage would you think it beneficial to have the extra (wrong inverter i have already) and possibly use it on a car for very small charging or the spare battery, or some cheaper batteries? Do you think the extra battery would be worth hooking up to the aforementioned alternator/bike to maintain the charge? When the battery is full where does the extra energy go from the alternator? I know car batteries have different usage than traditional PV systems in that they are meant for starting not maintaining. But charging smaller devices seems ok? As well I head that the alternator can supply 600 watts, so if i load 400 onto the system and the car is on the battery wouldn't be dwindled?

    In general how does using batteries while they charge affect their life?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Solar wiring questions (newb)
    As for the CFL's in my experience they dont last as long as incandescents nor are they nearly as functional. Can someone explain to me how a watt is a watt is a watt if the differences in the lights clearly show different wattages with "comparable" functions?

    A Watt is a Watt is a Watt: a fixed, finite unit of energy. It can be used to produce different kinds of work such as light, heat, or motion. If it is used in an incandescent bulb most of it goes to light, some of it to heat. If it is used in a heater most of it goes to heat, some of it goes to light. Heaters don't make good lights and lights don't make good heaters.

    The absolute proof of this is in comparing incandescents to CFL's: equivalent lumens, but a big difference in Watts because the CFL converts more of the power to light and less to heat than does the incandescent. LED's even more so; this is efficiency in practice.

    I've never had any trouble with short-lived CFL's; been using them for years and they have even outlasted some incandescent bulbs. As with all things, some are better than others. The shortest life on a CFL I've seen has been from the "enclosed" type (plastic dome to make it bulb-like). Some CFL's have poor power factor, some have undesirable colour temperature. You have to pick and choose.

    Now if the bear would just move over a bit I'll go back to sleep. :p
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: Solar wiring questions (newb)

    To put the comparison simply, compare lumens to watts. forget what the package says comparing a 15 watt cfl to a 60 watt conventional bulb. It is simply a matter of using the right tool for the job. I have used CFLs exclusively for nealy ten years, in my house, as well as in several vacation rental grid powered houses. I have replaced exactly two in all these years.

    LEDs a really the way to go, but the price has to come down to be really competitive. My current ones are ~40 watt equivalent and cost better than $10. When they break the $10 barrier (and as I need to) I will replace the CFLs. Like I said elsewhere, I love my Ikea reading lights, and my $9 Costco LEDs.

    Tony
  • frohickysmolder
    frohickysmolder Registered Users Posts: 11
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    Re: Solar wiring questions (newb)

    Alright I suppose I see what you are saying with reference to a watt is a watt.... It is the applications which differ, I'd still like to see practical studies comparing heat output of various technologies. Not because i'm questioning your points but because i think there are factors involved which might complicate things. you all sound very knowledgeable and i get where you are coming from.

    I will try to pay attention to the applications I use for the solar (less resistance = more applications). I still don't agree with the usage of CFL. But then again I have mercury in my mouth from evil corporate dentistry and I would only like to use objects that could be put in my garden (mad hatters anyone?) without sending me to an early grave. Sure you can bring it to home depot, but my guess is even a good 30% of them end up in the trash (and another 20% ghana). I gather batteries have similar destructive attributes to my garden, but batteries aren't replacing a benign technology such as the conventional light bulb. (light bulbs have also been the major subject of planned obsolescence so pardon me if i dont trust the technology establishment selling us higher priced poison filled bulbs, new and improved!) I also question the detriment of the light bulb to the environment. I believe there are far too many more destructive things such as cars, factory production, and the cattle industry for me to care about a light bulb. on top of that CFL's become an excuse for people to leave the light on, and they may well end up using just as much electricity.


    BUT back to topic, I still need some help! would 3 strings of 2 batteries at 24 volts be ok? if I could add a battery that would leave me around 600 ah which is about what someone said my panels would handle, is that right? maybe i should just add a battery then rather than the other scheme of rotating in a spare. Would i change the voltage from 24 to 36 with 2 sets of 3 batteries? and any suggestions on an inverter for this system would be much appreciated.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
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    Re: Solar wiring questions (newb)

    Yes, you can go with 2-3 parallel strings of lead acid batteries. Just keep the wiring equal electrical lengths (i.e., resistance) for each of the parallel current paths.

    And I still will push a DC Current Clamp Meter (here is a $60 one with DMM functions that is "good enough" for our use here).

    Go out a few times a month and measure "heavy" charging/discharging current through each parallel path (make sure currents are roughly equal between strings). And measure the voltage across each cell (or each battery). You are looking for "variations" between the strings... Anything too high or too low needs to be investigated because the current is (probably) not sharing properly (bad/loose connections, corrosions, open/shorted battery cell, etc.).

    Also, you should have a large amperage fuse or circuit breaker for each parallel string (in case there is a short circuit somewhere) to protect each string from over current.

    High Amperage Inverter Fuses & Breakers

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: Solar wiring questions (newb)
    I believe there are far too many more destructive things such as cars, factory production, and the cattle industry for me to care about a light bulb. on top of that CFL's become an excuse for people to leave the light on, and they may well end up using just as much electricity.

    The pursuit of the perfect shouldn't be the enemy of the better than,,, If you actually read some studies you will find that CFL have a significant impact on the decrease in mercury emission from conventional power plants.

    http://www.txchnologist.com/2011/the-mercury-myth-how-much-mercury-do-cfls-actually-contain

    From here:https://fortress.wa.gov/ecy/publications/publications/0704039.pdf
    Q: Are there any other benefits to using CFLs besides energy savings?
    A: The environmental benefits are significant. Replacing a single incandescent bulb with a CFL will result in
    the reduction of a half-ton of CO2 from the atmosphere over the life of the bulb. Saving electricity also reduces
    the emission of nitrogen-oxides, sulfur-oxides, and other pollutants from power plants. Mercury is a pollutant
    form coal-fired power plants, but the mercury saved by use of a CFL is much greater than the small amount of
    mercury in the bulb. If you combine the amount of mercury in a CFL bulb with the mercury emissions from a
    coal fired plant that produces the energy to run the bulb, the result is a 25 percent decrease in the amount of
    mercury used to light an incandescent. Not only is the CFL producing less gaseous mercury contamination than
    the incandescent, but in a CFL the mercury remains in a form that can be recycled.

    Not to beat a dead horse,, so I will end with that.

    Tony
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Solar wiring questions (newb)

    The bear snores a lot and keeps waking me up.

    Mercury, Arsenic, Lead, Uranium, et cetera are all naturally occurring elements.

    A pollutant is simply something that's not where it is supposed to be or wanted.
  • frohickysmolder
    frohickysmolder Registered Users Posts: 11
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    Re: Solar wiring questions (newb)

    you havent even passed the dead horse let alone beat him! I simply don't agree. So tell me then. Where does the mercury come from if you are using solar? Oh yea the CFL. plus they don't last. Are crazy expensive. Have I mentioned they take time to work making them useless for areas like closets and hallways? Have I mentioned they don't last when put on and off a lot? Just go look at paul wheatons experiments. I don't think CFL's have any ability to save the world and there are hundreds or thousands of things more important than forcing people to buy more expensive light bulbs.

    CFLs are around to make money. they are also around to make people think they are accomplishing things while corporates and bereaucrats run around poisoning everything else. it keeps people from feeling guilty from not stopping them. its a false flag
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Solar wiring questions (newb)

    Many forum members use CFL's. They are not "crazy expensive" and many of us have had great longevity from them. No one ever said they will "save the world" or any such hyperbole. They are more efficient at producing light than incandescents. LED's are even more so, but so far the price on them is still too high.

    No technology is perfect. Nor should only one solution to a problem be offered. Canada, for instance, has actually outlawed the sale of certain size incandescent bulbs, which is a stupid thing to do in my opinion; people should be intelligent enough to make such choices for themselves. It is a shame that this is not the case and that intelligent people are forced to suffer as a result.

    If the bear gets woken up again he just might take a swipe at someone; he's getting grumpy.
  • frohickysmolder
    frohickysmolder Registered Users Posts: 11
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    Re: Solar wiring questions (newb)
    The bear snores a lot and keeps waking me up.

    Mercury, Arsenic, Lead, Uranium, et cetera are all naturally occurring elements.

    A pollutant is simply something that's not where it is supposed to be or wanted.


    Yea but my basement had radon, that doesn't mean i left it there. Your point is obvious but the kids walking around on fields of mercury in ghanna was less obvious. we can't be trusted with concentrated uranium or mercury or hardly even lead. just because something naturally exists doesnt mean we concentrate it use it up for whatever purpose and stash it on some poor suckers lot in a country we will never see. But it happens, im not blaming you im just saying CFLs wont solve anything other than lighting with dwindling battery power.

    and no a pollutant is not something just where it is not wanted. it is also a concentration to harmful levels. simply moving soil around doesnt pollute, but filling it with buckets full of mercury does. not because it is where it isnt wanted but because its concentrated. the same goes for microbes we eat. we could eat botulism, probably do all the time, but its not enough to matter. unless you concentrate it its irrelevant. not just where we dont want it, but concentrated.
  • frohickysmolder
    frohickysmolder Registered Users Posts: 11
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    Re: Solar wiring questions (newb)

    I'm not sure what bear you are talking about. lol is that a threat or something! I dont mean to criticize anyone if thats what you think is going on. I just find it funny that sometimes people cling so heavily to the idea of cfls. why would they ban incandescents? because they are far superior. you say cfl is more efficient, is that efficient if you turn it on in the middle of the night to go pee and still cant see by the time you stub your toe on the toilet? point being that there are multiple ways to measure efficiency.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Solar wiring questions (newb)

    You must have been buying really poor quality CFL's! None of the ones I have suffer from such shortcomings as you describe. Incandescents certainly are not "far superior". I've had more of them burn out prematurely than the CFL's. Buy a cheap bulb (or anything), get a cheap bulb (or anything).

    I still think Canada's bulb ban is psychotic, though.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
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    Re: Solar wiring questions (newb)
    I will try to pay attention to the applications I use for the solar (less resistance = more applications). I still don't agree with the usage of CFL. But then again I have mercury in my mouth from evil corporate dentistry and I would only like to use objects that could be put in my garden (mad hatters anyone?) without sending me to an early grave. Sure you can bring it to home depot, but my guess is even a good 30% of them end up in the trash (and another 20% ghana). I gather batteries have similar destructive attributes to my garden, but batteries aren't replacing a benign technology such as the conventional light bulb. (light bulbs have also been the major subject of planned obsolescence so pardon me if i dont trust the technology establishment selling us higher priced poison filled bulbs, new and improved!) I also question the detriment of the light bulb to the environment. I believe there are far too many more destructive things such as cars, factory production, and the cattle industry for me to care about a light bulb. on top of that CFL's become an excuse for people to leave the light on, and they may well end up using just as much electricity.

    I try to point to conservation as being a very important goal... But I understand your concerns about mercury, lead, etc. in the environment. Personally, I have concerns about LED fixtures that use a pound of aluminum for heat sinking vs the tiny amount of glass and metal used to make the old filament bulb (mining, smelting, transportation, disposal--shifting operations from relatively regulated US/Europe to poorly regulated Asia and Africa, etc.).

    That carries through the batteries, acid, plastics, copper, solar panels and the heavy metals used in many thin film and as doping agents in silicon, etc...
    BUT back to topic, I still need some help! would 3 strings of 2 batteries at 24 volts be ok? if I could add a battery that would leave me around 600 ah which is about what someone said my panels would handle, is that right? maybe i should just add a battery then rather than the other scheme of rotating in a spare. Would i change the voltage from 24 to 36 with 2 sets of 3 batteries? and any suggestions on an inverter for this system would be much appreciated.

    However, I am also practical. Work with folks to help define/design a system that meets their needs (not mine, not the guy down the street, etc.). We do push conservation because off grid solar costs something like 10x what grid power costs in the US. So, any power you can save, can be a big help to keep system costs down. But, because power usage is highly personal--I (we) respect your choices in life. They are not "uninformed".

    So, work from the Battery Bank as you have spec'ed. 24 volt @ 600 AH.

    First, I am not a big fan of paralleled battery strings--But here is a recommendation on how to properly wire them to balance charging/discharging current through them (I like 1 strings, with 2-3 parallel strings maximum).

    Next, typically we recommend 1-3 days of "no sun/no charging" with 50% maximum discharge. A "two day" battery bank and 50% maximum discharge is a "balanced" off grid system and will use ~25% of the energy per day.

    So, such a bank would supply:
    • 24 volts * 600 AH * 1/2 days no sun * 0.50 max discharge * 0.85 inverter eff = 3,060 Watt*hours = 3.06 kWH per day

    Note that is enough power to run a 1,500 watt typical electric room heater for 2 hours per day from the battery bank.

    That is a "nice value". I suggest around 3.3 kWH per day for a "nice sized" cabin/conservation minded home, cost effective system (~100kHW per month). Note--You can draw down to 20% state of charge (80% of capacity) in an emergency too--Your choice (batteries will not last as long--but will certainly last for months of emergency usage with very deep discharge).

    Next, the typically maximum load for a flooded cell battery bank would be ~C/8 (~12.5%) of 20 Hour Battery Capacity:
    • 24 volts * 600 AH * 1/8 rate of discharge * 0.85 inverter eff = 1,500 Watt "nominal" max continuous inverter output

    And, a flooded cell bank can reliably support around a C/2.5 rate of discharge for surge loads:
    • 24 volts * 600 AH * 1/2.5 * 0.85 inverter eff = 4,896 watt surge (starting a well pump, etc.).

    So, the recommended inverter would be around 1,500 watt to 5kW maximum... "Good inverters" can supply upwards of 2x of rated power for a few seconds, so your rated inverter range would be around 1,500 to 2,500 watts recommended (or a bit higher). Larger inverters have higher losses--Sometimes folks buy two inverters--smaller one to run electronics, computers, lighting, cell phone chargers, etc... And a larger inverter to run tools in shop, washer, etc.

    Now, to recharge the battery bank. Two ways to "look at the problem". First is the rate of charge into the battery bank. Second is hours of sun on the solar array to replace a day's worth of energy use.

    So first, recommended rate of charge is 5% to 13% (of 20 Hour battery capacity rating). 10% is a "nice healthy" off grid value--But perhaps you will choose 5% for now because this is an emergency system and you will only plan on days or a few weeks of off grid power with backup genset and fuel supply... Your choice. If you wanted "full off grid", probably choose 10% or larger:
    • 29 volts charging * 600 AH * 1/0.77 panel+charger deratings * 0.05 rate of charge = 1,130 Watt array minimum
    • 29 volts charging * 600 AH * 1/0.77 panel+charger deratings * 0.10 rate of charge = 2,260 Watt array nominal
    • 29 volts charging * 600 AH * 1/0.77 panel+charger deratings * 0.13 rate of charge = 2,938 Watt array "cost effective" maximum

    Above are just rule of thumb suggestions... Nothing "magic" about the numbers.

    Next, how much sun do you get in a day? Using PV Watts for Berlin Germany with a fixed array tilted to 53 degrees up from Horizontal, we get:
    Month   Solar Radiation (kWh/m2/day)
    1      0.84     
    2      1.92     
    3      2.34     
    4      4.30     
    5      4.67     
    6      4.51     
    7      4.77     
    8      4.54     
    9      3.25     
    10      2.21     
    11      1.47     
    12      0.62     
    Year      2.96      
    

    Not great sun, If we assume 4 hours of "noon time equivalent" sun per day, such a system would need a genset for 7 months of the year to help the solar array (you pick your numbers/location/needs). Assuming 4.0+ hours of sun per day, a 3.06 kWH load would need:
    • 3,060 WH * 1/0.52 panel+controller+battery+inverter derating * 1/4 hours of sun per day = 1,471 Watt solar array minimum

    So the "optimal" solar array for your system would be in the range of 1,471 watts to 2,938 watts to support a 3.06 kWH load for 5 months of the year (4 hours minimum sun per day) with a 24 volt @ 600 AH battery bank.

    Questions/changes about my assumptions/clarifications?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • frohickysmolder
    frohickysmolder Registered Users Posts: 11
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    Re: Solar wiring questions (newb)

    Well that is an incredible amount of information.

    As it stands right now I'm probably going to hook up just the four batteries and use the fifth to rotate in. I like that idea primarily because both I bought 5 batteries, and I think it adds to the resiliency of the system without further purchases.

    So based on that it probably throws of some of your calculations, however I am going to need to let your post sink in so ill have to wait to clarify for you, but I have been thinking of keeping that inverter I have and using it singularly with the extra battery should the need arise.

    Besides it sounds like you are saying that the batteries I have (if i had the 6 for 600 ah) could use a bit more panels than i have. So my guess is that downsizing to 4 makes the system more fitting. However, I am going to guess that the 4 batteries at 400 ah couldn't be used to run a well pump? I havent really been considering usage of a well pump, im more thinking that i will just use a pulley and a pvc bucket from the well. I guess

    So do some of the emergency applications i have mentioned lose effectiveness when i reduce to 400 ah ?

    It sounds like in the winter my system will barely be able to do anything other than power up some minor electronics. and i am ok with that. i spent months camping in cold weather, and i have a basement which is a little more moderate than outdoors, I could probably hook it up to a pellet stove and I have been interested in adding a wood stove anyway.

    Thanks to everyone so much for helping, and bantering. I don't mean to criticize anyone as i said in the conversation about CFL. You all have helped me appreciate the true cost of electricity as has trying to develop this system. I do not believe we pay enough for grid electricity when we consider all the factors, and CFL's do have something to say about that.


    My batteries arrived today. Whew! Heavy. So now I have the main components (tho i will need a new inverter still, brands, specifics?), and I am ready to get started. Does anyone know of a good video that shows exactly how all these components are pieced together? A comprehensive look at the wiring? I guess what confuses me the most currently is the wiring of the breakers. For some reason i can't picture that.

    PS- have any of you ever seen the biolite camp stove? I just got mine in the mail today. its a cool gadget havent been able to try it out yet. It allows you to boil water over a little stove with a generator in it to charge USB devices. it also powers a little fan and an internal battery for the fan.