Advice greatly appreciated for purchasing solar system&sufficient number of batteries

CrystalCrystal Solar Expert Posts: 119 ✭✭✭
We are starting out with a very small affordable system that we plan on building onto in the future.
We will be running a laptop computer, small 1.4 watt fan for compost toilet, and possibly a few solar lights.
We already have a Honda 5000 watt generator that we should be able to use to charge batteries if the sun doesn't shine for a while.
We are located in MN.


Here is a list of the components we will purchase in the next month:

1- 200w Evergreen solar module
2- Trojan T-105 batteries
IOTA 12 volt 55 amp battery charger
SCI Mark 12 volt 22 amp charge control
Samlex Cotek 12 volt 600 watt true sine wave inverter

Will these components work well together?

In your opinion, are these reliable options?

Will two Trojan batteries be sufficient?

Is a battery meter neccesary?
If so, would the Trimetic model 2020 be a decent choice?

Am I missing anything that is will need to have?

Any suggestions and advice will be greatly appreciated!:D
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Comments

  • WindsunWindsun Solar Expert Posts: 1,164 ✭✭
    Re: Advice greatly appreciated for purchasing solar system!

    Not sure why you would want an SCI controller, they are almost 30 year old technology.
  • CrystalCrystal Solar Expert Posts: 119 ✭✭✭
    Re: Advice greatly appreciated for purchasing solar system!

    I didn't even realize that the SCI technology was that old.
    Thanks for the info.

    Would the Morningstar Tristar 45 be a better choice?
    What controller would you suggest?
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Advice greatly appreciated for purchasing solar system!

    Regardless of ANYTHING else, don't buy anything until you have done your homework! Do all the reading you can, here and elsewhere to learn all you can about small scale off grid applications.

    Avoid the mistake that too many make,, READY, FIRE, AIM!

    Tony

    Will write more later,,as will others, welcome to the forum,

    T
  • CrystalCrystal Solar Expert Posts: 119 ✭✭✭
    sufficient number of batteries?

    I am new to this and have so many questions...but here's just one.

    Would two T-105 batteries be sufficient in a small off-grid solar system?

    I'm located in MN and have a backup Honda gen. and plan to get one 200 watt Evergreen panel, as well as, the other components needed.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: sufficient number of batteries?

    those items will go together, but you will need other items like a controller, fuses, etc. also, i can't say how well it will work for you as i don't know the loads you plan on. do remember that solar is dependent on where you are, the time of year, and what weather is being experienced.
  • hillbillyhillbilly Solar Expert Posts: 334 ✭✭
    Re: Advice greatly appreciated for purchasing solar system!

    Tony's right on this, take some more time to really figure out what you need now and what you might need later. I'd say that two T-105's sounds like not a lot of storage, but that really depends on what kind of use you plan for them. Your loads sound very light now, but what are the chances that your "needs" will grow in a few years? It's worth considering a bigger battery bank, however you would also probably want some additional PV up as well. Right now your planned battery bank is a bit undercharged with just one 200 watt panel, a second panel would be good if you could swing it.
    Good luck
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: sufficient number of batteries?
    Crystal wrote: »
    I am new to this and have so many questions...but here's just one.

    Would two T-105 batteries be sufficient in a small off-grid solar system?

    I'm located in MN and have a backup Honda gen. and plan to get one 200 watt Evergreen panel, as well as, the other components needed.

    'Sufficient' is a question of how much power you need. Without determining your potential loads, you're guessing. Too much system and you've wasted power. Too little and the lights go out suddenly.

    Load will determine what size inverter you need and how much battery to power it. Battery bank size determines how much solar panel you need to recharge. Without the load info, you're lost.
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Advice greatly appreciated for purchasing solar system!

    The single most important thing that you can do is define the loads. A kill-a-watt meter is a useful tool to help do this. A couple of rule apply however, the first is that loads ALWAYS grow with time, and people almost always underestimate loads.

    Once you get a better sense of you loading, you can begin to design a system to power them. A couple of rules of thumb apply here as well. First, take the name plate rating of your PV array (in watts) divide that number in half to account for all system losses, and then multiply that number by the average number of hours of GOOD sun you can expect in an average day (seldom) more than four. That leave you the gross number of watt/hours you can reasonably expect to draw from a system on a daily basis. (on average) Example, 400watt/2x4=800wh/day.
    People almost always OVER estimate the amount of power they will get from a system!

    Next you have to build in some reserve for times of no sun. Most people suggest 3 days but that is dependent on personal needs. You also have to decide how far down you are willing to draw your batteries during an average cycle, and reserve draw. (never more than 50% and ideally no more than ~25% if you expect reasonable battery longevity)

    Then you need to plan on how you are going to charge from other sources, (grid/genny etc) and how to do that efficiently.

    In short, it makes best sense if all the hardware is sized for the expected loads such that the hardware is working ~75% of capacity. Charger controllers/inverters/chargers/gennies are most efficient when they are loaded nearer their capacity. For example, it makes no sense to run a 200 watt load on a 1.5kw inverter, as you will waste a substantial amount of power, instead run your load on a 300 watt inverter. Of course you can't size hardware to be perfect all the time, as loads and Pv charge currents vary, but by defining and designing well, it will pay dividends in better system ef.

    I'm sure there is more, but that is enough for now.

    Remember, define the loads, and understand that they will grow, and the PV won't put out as much as you think. That said, we live quite well on ~300watts of PV,a nd 4 T105s

    I suggest that you also read the following to get a better idea of battery performance:http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries
    http://www.batteryfaq.org/

    Tony
  • BB.BB. Super Moderators, Administrators Posts: 30,520 admin
    Re: sufficient number of batteries?

    If you are going to use 120 VAC appliances... Get a Kill-a-Watt meter and measure your actual daily power usage. Meter is also very handy around the home to find appliances that waste power.

    In general, a single 200 watt panel is not very large and will generate only a minimal amount of power--especially during the winter/cloudy weather.

    If all you need is to power a cell phone charger, a few lights, and a radio--it can work for you... However, if you want to power a bit more (laptop computer, some sort of data link, etc.)--you might want a second panel.

    Assuming you are very frugal with your energy usage--a single 200 watt panel can work pretty well for you. Tony/Icarus and his wife are in Ontario Canada have used 200-300 watts worth of panels over the years (using propane for the home fridge, gasoline powered washer, etc.)--so it can be done (even a laptop + satellite uplink).

    I think elsewhere you posted you have a 5kW Honda genset to... My suggestion would be to also get a small Honda eu2000i or eu1000i to power your loads/backup battery charging.

    Most generators tend to consume fuel at 50% of their full power fuel flow when operated at 50% or less of their capacity. The 5kW genset will use about the same amount of fuel at 2000 watts as it does generating power for a 400 watt load... That can translate into 0.25 gallons per hour or more to run small loads on a large loads.

    The Honda euX000i product line uses a alternator/inverter setup... Basically, it generates power which goes to an internal sine wave inverter. This allows the engine to slow down when supplying smaller amounts of power and extend it "fuel efficient" operating range down to 25% (or less) of load.

    An eu2000i has the advantage of being smaller (closer to your actual loads) and more fuel efficient at lower power levels. At ~400 watts, it uses about 0.073 gallons per hour (only 30% of the fuel usage with the larger 5kW generator on my imaginary 400 watt loads).

    If you are going to be spending significant amount of time at the remote location (9+ months of the year)--it really pays to look at every aspect of your life (power requirements, electric vs propane fridge, etc.) and what you use to make that power...

    If you are only there 10-20 weekends a year--you can be a bit less detailed oriented and the costs tend to favor using the genset more (your only costs are for fuel when you are there). Solar make very good sense when it is used 9+ months of the year to gather/make useful energy.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 30,520 admin
    Re: Advice greatly appreciated for purchasing solar system!

    To make Tony's math a bit clearer to read ;):

    400watt/2x4=800wh/day

    400 watts of panels * 4 hours of sun per day * 50% sys eff = 800 Watt*Hours per day

    In the end, define your loads first, then design the system. Also, will you be using 12 VDC loads too or not. Higher voltage battery banks are better for larger installations (roughly >1,000 watts of load).

    There are other, better, controllers out there--but to define which one really depends on other issues... Battery Bank voltage, How many watts of solar panel will you have/be adding in the near future, how sensitive you are to price, etc.

    In the end, you probably pay around $0.10-$0.30 per kWhr for power you use at home. For off grid power, you will be paying $1.00-$2.00+ per kWhr (assuming 20 year life, battery replacements every 4-8 years or so, etc.)--So be aware that any "exce$$" power you con$ume will come with a $ignificant co$t.

    Once you know your loads, it is much easier to design a system that will make you happy. While it is possible to expand a system somewhat--Making a much larger system can result in you "tossing" much of the original equipment (EBay/used sales can recover some of the costs).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Advice greatly appreciated for purchasing solar system!
    BB. wrote: »
    To make Tony's math a bit clearer to read ;):

    400watt/2x4=800wh/day

    400 watts of panels * 4 hours of sun per day * 50% sys eff = 800 Watt*Hours per day

    -Bill

    Sorry Bill, I had written a much better worded response filled with pithy witticisms and somehow it disappeared into the ether, so my follow up was indeed a bit terse. ( I hate that when that happens! There must be some button I scroll across that makes it delete, but I can't find it!

    Besides, I have never been accused of being too clear,,,,

    T
  • BB.BB. Super Moderators, Administrators Posts: 30,520 admin
    Re: Advice greatly appreciated for purchasing solar system!

    Yea... that is it, all of my better posts where eaten by my browser too. ;)

    I use FireFox and sometimes my cursor "bounces" out of the edit window and when I use <Backspace> it instead takes me back to other URL's instead.

    You can use the "history forward" button and the post is almost always still there.

    If you are typing and a huge chunk of text gets accidentally selected and deleted--You can use Cntrl Z (^Z) on a Windows PC to recover several levels of deletions.

    I have a weird problem with FireFox that every once or twice a month that the "/" key takes me into a "link search" window--which then I press <Backspace> because I don't notice the cursor is not in the edit window (and leave the posting page).... I have close FF and reopen when that happens.

    -Bill

    PS: Note that I had a better and more coherent post before this one but my browser ate it. :roll::p
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Advice greatly appreciated for purchasing solar system!

    Apple has a nice "undo typing" command,

    T
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: sufficient number of batteries?

    Crystal,

    Please try not to duplicate your questions in various threads. I believe you have a thread going with very similar issues, and it is much simpler for all to only have to answer once.

    Tony

    MODs,, you might look to merge these two threads.
  • BB.BB. Super Moderators, Administrators Posts: 30,520 admin
    Advice greatly appreciated for purchasing solar system&sufficient number of batteries

    Taking Tony's advise...

    Merge Crystal's two threads... Basically all referring to one system.

    Just continue the discussions here.

    -Bill (Moderator)
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CrystalCrystal Solar Expert Posts: 119 ✭✭✭
    Re: Advice greatly appreciated for purchasing solar system&sufficient number of batte

    Thanks for all the helpful advice. I am definately going to take more time to make the best choice for our needs...which are very minimal. We have learned to live sustainably without electrical power for the past 1 1/2 years.
    We have always planned on solar power and now have just started to look into it.

    So, is a solar system something that you can accomplish little by little, with a "pay as you go" lifestyle?
    Or, is it more economical, in the long run, to purchase components that will handle bigger loads in the future?

    I suppose down the road, when we need a larger battery bank, we should buy all new batteries, and get rid of the older one's. As well as, purchase a larger control and possibly inverter.

    I'm sure I will have many more questions in the near future. I think that the most difficult part for me to understand is the math involved...
  • BB.BB. Super Moderators, Administrators Posts: 30,520 admin
    Re: Advice greatly appreciated for purchasing solar system&sufficient number of batte
    Crystal wrote: »
    So, is a solar system something that you can accomplish little by little, with a "pay as you go" lifestyle?
    Or, is it more economical, in the long run, to purchase components that will handle bigger loads in the future?

    It is tough, in a cost effective manner, to grow a solar / off grid system...

    Inverters are sized to your loads. Batteries are sized to the inverter. Charge controllers are sized to the amount of planned current, solar arrays and gensets are sized to the power needed, etc...

    If you are looking to grow a system and conserve capital outlays...

    Start with conservation. It is reasonable to expect that spending money/time on conservation will save you lots of money vs spending it on solar/batteries/fuel...

    Next, size your loads. If your average power is relatively low (lights, laptop, radio, etc.)--you can build a small system with 200-400 watts of panels and 4-8 batteries and be pretty happy. Use a cold-box and propane for the fridge. Your solar system with a DC RV style pump probably will probably pump your shower/sink water.

    For larger loads, use a generator to pump water into a storage tank, run the washer, vacuum cleaner and such in the morning.

    Thinks to look at adding up front--A good Energy Star refrigerator for a full time home will save money and hassles vs a propane fridge. If you want to play around... Converting a chest freezer into a chest refrigerator can be a nice solution too.

    The next step up is to size the system for your ideal loads (microwave, washer, drier, well pump, etc.)... You will probably dump your small system (sell it to a friend or keep for backup power) and start over with a larger system.
    I suppose down the road, when we need a larger battery bank, we should buy all new batteries, and get rid of the older one's. As well as, purchase a larger control and possibly inverter.
    Batteries are hard to add extras too a couple years down the road. Larger systems usually need higher voltage inverters (24 or 48 VDC). And the solar panels need to be (sort of) matched as you add more--may be a bit more work a few years down the road).

    The major MPPT Charge Controller (MPPT type) generally will work with 12, 24, or 48 VDC battery banks--so you can get a nice one for the small setup and use it with a larger system too.
    I'm sure I will have many more questions in the near future. I think that the most difficult part for me to understand is the math involved...
    It is hard to grab the entire problem at one time.... Focus on a piece at a time. First, your loads and how do to that math. The rest pretty much falls out from those calculations (not to say that spec'ing a complete solar off grid system is easy either--having somebody to help/hired--especially the first time or larger system--is usually worth the money).

    You learning the basics about the system will help a lot. You can double check that the installer knows what they are doing and you can tell them what you need--Makes it nicer for everyone and you will not have many surprises.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Advice greatly appreciated for purchasing solar system&sufficient number of batte

    Somethings grow better than others, and to some extent it depends on the time line. My first suggestion is start with a charge controller that is big enough. I personally am on my third, each getting bigger than the last as the PV gets bigger.

    Batteries shouldn't be added to after a year or so, but on the other hand, if you are willing to sacrifice some battery life, new batteries can be added. Pv panels can always be added, the charge controller issue not withstanding.

    Here is what I would suggest, in addition to the "ready, fire aim" advice given earlier.

    I would consider a charge controller in the 30 amp range, like the Rouge MPPT, or the new Morningstar. A MX 60 or 80 is pretty big, pretty expensive. If you grow down the line, you can parallel another on top.

    I would start with ~200-300 watts of PV, and 4 T-105s. Big enough to have some power,cheap enough to kill a few before you get your feet wet, and cheap enough to add some to without breaking the bank.

    I would start with a Suresine 300 sine wave inverter. Once again, you can parallel another if your loads grow, (as long as no individual load is bigger than 300 watts).

    I would also get a Honda Eu 1000 or Eu 2000 with a Xantrex TC series charger to keep the batteries topped up when either the loads are too great or the sun is not great enough.

    Good luck,

    Tony

    I'll give you my spiel on fridges tomorrow!
  • hillbillyhillbilly Solar Expert Posts: 334 ✭✭
    Re: Advice greatly appreciated for purchasing solar system&sufficient number of batte

    Crystal, my wife and I lived for years on little to no power and never really minded too much, but it's funny how once there is power available we have continued to find more and more ways to use it. Our PV system started VERY SMALL: a 110watt panel, a marine battery, a 25amp charge controller and some 12V lights. It's grown a lot now to a 1200watt array, a 24Volt 700amp hour battery bank, a 60 amp charge controller, 3500watt inverter... etc. It can be tricky to grow a PV system later on down the road cheaply, it's easy to add components (other than batteries) but often you end up having compatibility issues and thus it tends to be more costly. One idea (just a random thought) if you think that your needs/wants might grow in a few years: buy a couple of used/cheaper batteries sized to your current loads and count on them lasting you a few years and then when it's time to replace them you can decide if you wish for a larger system or not. Other components can be purchased with the option for growth later on too, it's just that they tend to run you more money up front and end up being a waste if you don't upsize later on.
    As far as the sizing of inverters and batteries the main thing that you can't easily change is the voltage, since the inverters are all for a specific voltage the battery bank must meet that. You can however reconfigure a battery bank at a later date if you have the right combination of batteries (for example 4 6V batteries can be made into a 12V or 24V battery bank). I'm kind of a fan of going for a bigger inverter if you think you may grow your system later, the drawbacks are that they are less efficient for a smaller system and cost more upfront, the advantages are not having to purchase an inverter that is later on is redundant (more cost overall) or of a different voltage, also most of the larger inverters that I know of allow you to charge your batteries via the generator. I'm not sure off the top of my head if there are any smaller inverters out there now that can do this, and if you're off grid this is a very important feature.
    As for Charge controllers, if you do spring for an MPPT unit then you'll have an ability to run a wider range of voltage combinations from the PV array to the charge controller and the charger will step that voltage down to meet the battery voltage. This can make a huge difference if you wish to add more panels later or change your battery voltage. An Mppt unit would allow you to for example run anything from a 12V to 60V nominal array and charge your 12V battery bank, and if you switch to 24V later you can simply rewire the PV array to anywhere from 24V-60V (or possibly higher).
    The PV panels are for the most part the easiest to add, the only real limitations will probably be: lack of space for additional panels, and matching new panels to existing voltage and current (I've had trouble with Evergreen discontinuing panels and then having to mix and match a bit when we wanted to upsize). You may also have issues with the charge controller's capacity, and the batteries voltage (these can dictate the numbers of panels that you can work with; sets of 2, 3, or 4... etc)
    As for the numbers to start with I think that Tony's are a pretty good rough starting point to consider.
  • BB.BB. Super Moderators, Administrators Posts: 30,520 admin
    Re: Advice greatly appreciated for purchasing solar system&sufficient number of batte

    By the way, regarding the composting toilet... Many need a heater for proper operation, especially in cold climates. Electric heaters tend to be big consumers of power on a solar system.

    There has been a few discussions here about the problems of composting toilets and solar power... Such as this one.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CrystalCrystal Solar Expert Posts: 119 ✭✭✭
    Re: Advice greatly appreciated for purchasing solar system&sufficient number of batte

    Thank you so much for all the great reply's. I have decided that we will definately go with an MPPT charge control. It is worth the extra cost.
    I have been reading and learning a bit more, however, I have a few more questions:

    One issue that I don't quite understand is the 67.4 watt loss?
    When the Evergreen 200 watt panel puts out 11.05 amps and battery is 12 volts, so you take 11.05 amps X 12 volts =132.6 watts.
    Is there a way that you can get around this substantial loss?
    Will the MPPT charge control help with this issue?

    There has not been discussion on the neccesity of having a meter. Do I need one for the system to run optimally?
    It's funny how once there is power available we have continued to find more and more ways to use it. Our PV system started VERY SMALL: a 110watt panel, a marine battery, a 25amp charge controller and some 12V lights. It's grown a lot now to a 1200watt array, a 24Volt 700amp hour battery bank, a 60 amp charge controller, 3500watt inverter... etc.

    I realize that once we have solar power we will most likely want more, however, I don't forsee that we will need more than 400 watts. So, I figure that we will be able buy another panel and add a few more batteries and we should be all right. I understand that it would be best to buy all new batteries when adding.

    We would still be able to run 12 volt system if we had a total of 4-8
    6 volt batteries...correct?

    I want to make sure that I am in complete understanding of this system before we have it in our house and find that it doesn't work the way we thought it would.
  • CrystalCrystal Solar Expert Posts: 119 ✭✭✭
    Re: Advice greatly appreciated for purchasing solar system&sufficient number of batte

    A few more questions:
    I would consider a charge controller in the 30 amp range, like the Rouge MPPT, or the new Morningstar. A MX 60 or 80 is pretty big, pretty expensive. If you grow down the line, you can parallel another on top.

    Would the Morningstar 15 amp MPPT charge control work?
    Then I could add another down the line. Right now our budget won't allow the larger 30 amp MPPT.

    It is recommended that the battery charger be rated for about 15% to 30% of the battery amp-hour capacity. Since I will have 2- T105 that equals 450 amp-hours it would be best to have a charger that is between 67.5 amps and 135 amps...correct? Or would it be all right to go with the 55 amp IOTA charger?

    Thanks Again!;)
  • BB.BB. Super Moderators, Administrators Posts: 30,520 admin
    Re: Advice greatly appreciated for purchasing solar system&sufficient number of batte
    Crystal wrote: »
    One issue that I don't quite understand is the 67.4 watt loss?
    When the Evergreen 200 watt panel puts out 11.05 amps and battery is 12 volts, so you take 11.05 amps X 12 volts =132.6 watts.
    Is there a way that you can get around this substantial loss?
    Will the MPPT charge control help with this issue?
    Yes, an MPPT type charge controller will do better... You can read about them here:

    All About Charge Controllers
    Read this page about power tracking controllers

    MPPT (Maximum Power Point Tracking) charge controllers are different from PWM (Pulse Width Modulation).

    PWM are simple and reliable, and for smaller systems, work very nicely. But they will do what your example says:

    11.05 amps X 12 volts =132.6 watts.
    11.05 amps X 14.5 volts = 160 watts.

    Basically, as long as the panel voltage (Vmp) is greater than the battery voltage (+2 volts for wiring/controller drops), 11.05 amps is the maximum you will ever get out of the panels+PWM controllers (on an "ideal" day). The battery charging current is equal to the solar panel array current.

    However, the MPPT Charge Controller uses a switch mode power supply inside the charge controller to take the "high voltage/low current" from the solar panels and "down convert" it into "low voltage/high current" for the battery. Basically the equation is:

    11.05 amps*18.1 volts of panel (Imp*Vmp)= 200 watts = 14.5 volts * 13.79 amps into battery (- 5-1-% losses)

    There are many reasons to use MPPT charge controllers (makes building bigger systems and longer wire runs to solar panels more practical). And on very cold days, the MPPT controller can get you 10-20% more power too.

    On the downside, MPPT is more expensive vs PWM. And, for smaller arrays (less than 400 watts or so for the large 60+ amp controllers), there are more losses inside the MPPT controllers and they tend not to be worth the extra money (extra power they gather is lost inside running the switch mode power supply). Morning Star does have a small MPPT (very nice) that can run well with a maximum of ~200 watts of panels (12 volt system) or ~400 watts (24 volt system).

    A highly recommended option for Charge Controllers is the Remote Battery Temperature Sensor (required for Morningstar 15 amp MPPT charge controller). Will correct charge controller output voltage based on battery temperature. Usually, charge controllers will charge the bank better (faster and higher state of charge) with a RBTS setup.
    There has not been discussion on the necessity of having a meter. Do I need one for the system to run optimally?
    Meters that you probably will need:
    1. Digital Multi-Meter (very handy to diagnose)
    2. If you have flooded cell batters, a Hydrometer (with thermometer)
    3. A Battery Monitor (very nice to have with flooded cell, almost necessary for AGM)
    4. Some charge controllers have optional meters. Pretty nice to have, but a Battery Monitor + DMM can tell you much of what an optional CC meter can.
    I am a big fan of Battery Monitors--But others here find that they are not ideal or 100% accurate (especially as batteries age).

    I believe the Percentage State of Charge reading is accurate enough, and for the people using the cabin that did not pay for the battery bank (i.e., your kids, guests, etc.)--it is easy to tell them if they see:
    • <75% state of charge, cut back on loads and/or start the genset (especially if cloudy weather ahead or it is winter time).
    • <50%, start the genset immediately to prevent long term battery damage.
    • >85%-90% state of charge, they can turn off the genset.
    Your choice.
    I realize that once we have solar power we will most likely want more, however, I don't forsee that we will need more than 400 watts. So, I figure that we will be able buy another panel and add a few more batteries and we should be all right. I understand that it would be best to buy all new batteries when adding.
    Are you sure about your loads and how much power 400 watts of solar panels+batteries+inverters will supply for you in your region?

    Regarding batteries--You can add new ones to an old bank... But the new batteries will tend to not last as long vs being installed in a matched bank.

    The worst case is you have a bank of xx batteries and replace them one at a time with new batteries--The new batteries will take most of the loads and wear out much faster. If you have a set, and if one battery fails early--it is certainly OK to replace it and get another few years from the rest. Then replace the whole bunch several years later.
    We would still be able to run 12 volt system if we had a total of 4-8
    6 volt batteries...correct?
    Personally, I do not like to parallel batteries at lower voltages (such as 12 volts). You have to use much heavier wiring, fuses in each string, and can have problems with current sharing or one shorted cell/battery taking down the whole bank. Personally, I would avoid more than two or three parallel strings.

    If you don't need a lot of power--12 volts can be cheap and easy to get 12 VDC appliances. The MorningStar 300 watt 12 VDC pure sine wave inverter is very nice.

    If you are going to use an AC inverter for all of your power needs anyway (no 12 volt or 24 VDC loads)--it is almost always better to go with the higher voltage. Fewer parallel strings, easier to diagnose battery problems (in my opinion). And your wiring/fuses/breakers/switches are smaller/cheaper and easier to wire.

    The "full size" MPPT charge controllers can work with 12, 24 or 48 VDC (just a setting in the charge controller). And the inverters are almost the same price in any of those voltages (smaller inverters tend to be more available in the 12 volt range).

    Also, the MPPT Charge Controller Maximum array wattage goes up with higher battery bank voltage:

    60 amps * 15 volts = ~900 Watt maximum array
    60 amps * 30 volts = ~1,800 Watt array
    60 amps * 60 volts = ~3,600 Watt array

    So, a higher voltage battery bank can support a much larger array with the exact same MPPT charge controller (of course, check specifications of the units before you purchase).
    I want to make sure that I am in complete understanding of this system before we have it in our house and find that it doesn't work the way we thought it would.
    Always a good plan.

    You could start with 400 watts of solar panels, a "large" battery bank (5% of bank capacity to match 400 watt panels). Have a good backup generator/battery charger ready. And if you need more power, you can slap on another (up to) 400-600 watts of panels and reduce your generator runtime if you find out that you need more solar power.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 30,520 admin
    Re: Advice greatly appreciated for purchasing solar system&sufficient number of batte

    A 15 amp MorningStar MPPT charge controller is one of the best units out there.

    Not cheap, and only good for ~225 watts of panels maximum with a 12 volt battery bank.

    For 400+ watts of panels, you would need two of them (pick the 30 amp Rogue instead of two MorningStar?), or pick a 24 volt battery bank (~450 watts of panels maximum).

    Notice that at 400 watts, you are right on the edge of the small to mid range controllers. If you decide to expand with another 400 watts of panels, you would need a second controller (or new, larger controller) at that time. (EBay the used controller, or save it for a spare).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Advice greatly appreciated for purchasing solar system&sufficient number of batte

    "We have learned to live sustainably without electrical power for the past 1 1/2 years..."

    Shiney!, You'll do just fine!

    I lived for many years [email protected] watts of panels, ran a MSW inverter, 1 or 2 compact floresent lights, laptop, a MP3 player or radio, a couple 10" O2Cool fans in the summer.

    After 3-4 years I decided I wanted AC (even more than a fridge!) and purchased @900 watts of panels (added another 340 watts this year, just couldn't pass up $2 a watt delivered)

    All of my old system is down now other than the batteries, the one thing I would have done different is to buy the panels in pairs or start with a 24 volt panels (and their need for a mppt charger if I was running 12 volt system)

    I would rather see you have the additional panel and a MSW inverter, laptops run on them all the time in vehicles, I have heard of problems but rarely. I think every thing your suggesting would run fine on MSW. at $20-30 for a 300 watt you'll not have a problem throwing it in the closet to use as a backup if you choose to add a refridgerator.

    I'd also go on the cheap for your first set of batteries, Sams Club will have 6 volt golf cart batts for @$72 compared to what ever your paying for Trojan $110+? If you don't have a Sams Cub or Costco near by check with friends. if you don't have a membership ask around, I just used my Sams club membership for a forum member here (I think).

    When I went to a larger system, I switched to 24 volts, I had 3-25+year old - 55 watt panels and a 50watt that was 7-8 years old. They were not a good match voltage wise, important in running panels in series. I ran 2 of the 55 watt panels together until this year when I added the 340watts of panels and really have too much array for the 4 golf cart batteries which I had with the old system in a 2strings of 2 batts and switched to 1 string of 4 batteries.

    I would not fear an SCI but prefer a C30 xantrex, I have a Rouge! and like it but my system still runs through a C60 charge controler which came with my Power Center (purchased to meet code) the Rouge is a fine unit but does not have UL listing. I would skimp here as well knowing that your producing more power(with 2 panels) than the MPPT would add. I really like the Rouges meter functions and would rather see you purchase it than a Trimetric and a C30 if your not worried about meeting code.

    I spent 8 months cycling with a 10 watt panel and a couple small 6 volt batteries in a total loss system (no controller) charged in series and used in parrellel at night to run a flash light, radio, and a mini TV I picked up along the way,after living with out, you'll be content for a while to switch on a real light!
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • mike95490mike95490 Solar Expert Posts: 8,764 ✭✭✭✭✭
    Re: Advice greatly appreciated for purchasing solar system&sufficient number of batte

    A single 200W panel, seems a bit light, unless you are really careful about your loads.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • hillbillyhillbilly Solar Expert Posts: 334 ✭✭
    Re: Advice greatly appreciated for purchasing solar system&sufficient number of batte
    BB. wrote: »
    I am a big fan of Battery Monitors--But others here find that they are not ideal or 100% accurate (especially as batteries age).

    I believe the Percentage State of Charge reading is accurate enough, and for the people using the cabin that did not pay for the battery bank (i.e., your kids, guests, etc.)--it is easy to tell them if they see:
    • <75% state of charge, cut back on loads and/or start the genset (especially if cloudy weather ahead or it is winter time).
    • <50%, start the genset immediately to prevent long term battery damage.
    • >85%-90% state of charge, they can turn off the genset.

    You could start with 400 watts of solar panels, a "large" battery bank (5% of bank capacity to match 400 watt panels). Have a good backup generator/battery charger ready. And if you need more power, you can slap on another (up to) 400-600 watts of panels and reduce your generator runtime if you find out that you need more solar power.

    -Bill

    I think this is all really solid advice here Crystal. Regarding the battery monitor, I am one of those here who has learned the hard way that they are not always a completely accurate representation of weather or not the batteries are completely charged. That said I still think it was one of the best purchases in our system for several reasons:
    number one, is basically what Bill said about being able to at a quick glance know (at least roughly) where you are at on the discharging side of things, other handy things are being able to watch how your battery's perform in many different ways. You can catch how much certain loads are really drawing at the battery terminals, etc... Overall they are a very handy and educational tool, the only caveat on them is that they don't tell you for certain when your batteries are fully charged as the Amps out/Amps in doesn't represent exactly how a battery is charged. But with some practice and an awareness of the health of the batteries, you can start to see patterns, and very well may catch problems earlier too. Ok that was a very wordy way of saying get a battery monitor! :-)
    I'd also strongly second the advice in the final paragraph, start out with a bit bigger battery bank, a small solar array and a generator. See how things go with that, add PV as needed. Do check into how you will use the generator to charge the batteries, you'll either need a separate AC/DC charger, or purchase an inverter that is also a charger (this worked best for us in our case). As for the sizing of the charger, I don't think you need to go quite that big, but it really depends on how much you are trying to charge the batteries, and how quickly you wish to do so. You can recharge batteries up with a very small charging current, if you have the time... usually 5%-20% is a good middle of the road average guess. One thing would that would demand a larger charger would be if you have any additional loads on the batteries while charging with the generator (or if all loads will be powered directly by the generator). Given the size of our loads that you have now, I'd say that a 10% charging rate would probably be fine (this is though just a very rough guess, you may want to sit down with a calculator and crunch some numbers on that). If you can live on 400 watts of PV that's great! We did this too, in fact we lived for quite a while on a single 110 watt panel and a few DC lights... had fun doing it too, but slowly siren song of the creature comforts of the modern world lured us in...
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Advice greatly appreciated for purchasing solar system&sufficient number of batte

    A couple of other thoughts to futher muddle your head.

    As I have suggested, your loads WILL grow with time. No matter how frugal you have been, slowly without even noticing, you will leave lights on a bit longer, listen to the radio a bit more, plug the PC in more, watch a DVD on the lap top, pump more water or whatever.

    As Hillbilly suggests, go with a bigger battery bank up front, large enough charge controller to grow into, especially if you are going to go with an MPPT, and count on using the genny to keep the batteries up until the Pv can grow into the system. I would buy a battery monitor on day one! (Hydrometer too!)

    It does go back to the basic premise: calculate your average expected load (add in a fudge/growth factor) and then work backwards. Take your expected loading in wh and figure out how many panels/batteries you need to provide this load on an average basis. (Including some reserve)

    Tony
  • hillbillyhillbilly Solar Expert Posts: 334 ✭✭
    Re: Advice greatly appreciated for purchasing solar system&sufficient number of batte

    Forgot to mention that IF you do decide to start out with a system with the intention of possible future expansion, I would recommend a 24V system (48V is even better, but it doesn't sound likely that your system will really grow so big as to need that high of a system voltage). The means buy batteries in a quantity that can be configured to 24V, either now or later on. Buy a 24V inverter, or look at purchasing a very small 12V inverter that you don't mind having to replace later on (rather than an expensive 12V inverter upfront sort of "locking you in" to that system voltage). Purchase a charge controller that can work at a variety of voltages, most MPPT chargers do this.
    The only real reason that I could see for a 12V system would be if you were looking at using a number of 12V loads. I've found that for the most part it's easier to just wire the whole place up for AC loads and run all or most of your loads at 110V AC.
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Advice greatly appreciated for purchasing solar system&sufficient number of batte

    For a number of reasons, I disagree. I think that a 12vdc is a great starting system. The big advantage is that all manner of hardware is available in 12vdc from fans and radios and tvs etc. ( Many are also available in 24vdc from truck stops, but the selection/availability is more limited).

    24 vdc means lower wiring losses, but in small panel arrays, keeping panel nominal voltages above battery voltage is easier if you have lower voltage battery bank.
    For example, most mppt controllers are more efficient with a 24vdc in put and a 12vdc out put. (Or 48/12 or 48/24 etc) giving the mppt some "headroom". So in my case, I can wire my panels in a collection of 24vdc (nom) sub array, and down convert to 12 vdc fairly efficiently, instead of wiring them to 48 vdc. The advantage is if one part of the array gets shaded, the output will only drop off from that sub array. If I had wired four panels to 48vdc, and shade hit one, the output would drop off by as much as 90%. On the other hand, with 2 pairs of pv wired into 24 vdc sub array, the same shading would only effect potentially 1/2 the out put. (Not very well written, but I hope you get the idea!)

    Tony
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