Help before I buy system

I will be purchasing a PV system within the next month and would like as much advice as possible. I have been reading a lot and have come up with an equipment list I would like to use.

4 Suntech stp 210 watt-- 26.4v--7.95 amp solar panel

1 Outback Flexmax FM60-150 charger

4 Universal Battery 12v --110 amp hour

1 Aims 7000 watt Modified sine wave inverter


Not sure about solar panels and how long they will produce the 26 volt. Does the voltage drop off with light levels or the amperage?

What is the best way to run this system 12 volt or 24 or 48 ?

I live in north Georgia.

Comments

  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Help before I buy system

    Please,,please, please,,

    Before you buy anything, do some more reading!

    Ask questions and get some answers before you ready, fire aim!

    The first question is what are you buying this hardware for? Back up, UPS, off grid? What are you expecting to run off it? For how long?

    Until you know the answers to those and a bunch of other questions you should hold off buying anything IMHO!.

    A couple of questions that come to mind right off the bat are, Why are you buying a 7kw inverter with only 210 watts of panel, and only 120 amphour batttery? Why are you buying a ~50 amp controller for only ~ 8 amps of PV.

    Start to answer those questions and then you will know if you are making the right choices,, if not you will be doing it backwards,

    Tony

    PS I have also never heard of the panels you propose or the battery you wish to buy,,, not a bad thing perhaps, but raises the radar a bit. Who are you buying from might also be a relevant question.

    PPS I'm sorry, I missed the number 4 before both the controller and the battery. Makes more sense now. (I'm drugged up for a pain issue right now, so ignore most of what I say,,, no more so than normal!)
  • System2System2 Posts: 6,290 admin
    Re: Help before I buy system

    I will be using this system for a back up. I want to expand later to 8 panels and try to go off grid.

    I did not mention that I have a well pump that requires 220v at 10 amps so I selected the Aims inverter that produces 220v and will have enough power when I expand later.

    Thanks for responding. I am still reading and have started to ask the questions. Will probably start ordering after the first of the year.
  • BB.BB. Super Moderators, Administrators Posts: 31,918 admin
    Re: Help before I buy system

    I see that you are buying 4x210 watts of solar panels or 840 watts... A fairly good sized system for an off-grid cabin.

    And the Outback controller is a good choice too (at first glance).

    The 7kW AIMS inverter is a wild card here... Do you need such a large inverter? And what kind of power output are you expecting from your system?

    A 840 watt solar panel system would generate for Athens Georgia (use Derating Factor of 0.52 for off-grid system and 1kW for solar panel size--smallest number allowed by program), very roughly, an average maximum (how do you like that term? :roll: ) of 2-2.5 kWHours per day of useful power...

    Your 7kW inverter, assuming you use it at 50% capacity (3,500 watts) would use up 2 kWhrs of solar power in:

    2kWhrs per day / 3.5kWhrs = 0.57 hours or 34 minutes per day

    This setup may make sense (for example, you are pumping ~15 minutes of water per day into a cistern)--but, I would wonder if your inverter power expectations are way larger than the capabilities of your system.

    Regarding 12 volt. 24, or 48 volt system... That is based on your inverter requirements/capabilities... For example:

    7,000W inverter * 1/85% efficiency / 10.5 volt (minimum bat voltage) = 784 amps
    7,000W inverter * 1/85% efficiency / 42 volt (minimum bat voltage) = 196 amps

    A simple, single, 120 amp*hour storage battery, could probably, at most output around 400 amps (and quickly overheat and warp/damage the plates).

    Typically, I would suggest that a limit of ~100 amps maximum continuous for your inverter's DC input... Or ~1kW at 12 volts DC, or for a 4kW (or larger) system, use a 48 volt battery bank.

    And, if you ever tried to pull 3.5.kWatts from a 120 amp*hour battery:

    120AH * 12 volts / 3,500 watts = .41 hours until dead (24 minutes)

    In reality, such a battery would probably last less than 1/2 the time under such heavy loads... and given that you should never regularly below 50% capacity (1/2)--you are now down to 1/2*1/2*24min=6min of useful energy... Or less, if you try to avoid discharging more than 20% maximum average (80% state of charge), it would be recommended (for long battery life) to power a 3.5kW load (1/2*0.2*24min=) 2.4 minutes per day of use...

    If you need such a large system, look for posts from user "Adas"... He is from Hawaii and runs a large fabrication business (including arc welders?) from a solar system using large AIMS inverters... From his signature:
    Office System. 3940W * BP 40x70W * Sun 12x190blems * 1xFX80 * 2xMX60's * 4x625AH 24(36)v Batteries (Used Forklift Type)
    Warehouse System 4560w * Sun 24x190Wblems * 2xFX80's * 4x875AH 24v Batteries.(Used Forklift Type)
    Otherwise, understand your load requirements (typically in Watt*Hours or kWatt*hours) and work backwards to size the battery bank, the inverter, charge controllers, solar panels, backup generator, etc... If your loads are small (~15 amps maximum at 120 VAC)--take a look at that kill-a-watt meter line to start measuring your requirements.

    wind-sun_2032_3349941Kill-A-Watt AC Power Monitor Meter
    P4400 Cumulative Killowatt-Hour Monitor
    Regular price: $39.00
    Sale price: $27.50, 2/$54.00, 12/$295.00

    wind-sun_2035_3196929Kill A Watt P4320 Power Strip
    Kill A Watt power monitor strip with surge protection
    Regular price: $99.95
    Sale price: $78.85

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 31,918 admin
    Re: Help before I buy system

    Mr. Old Man,

    Generally, solar power does not make a lot of sense as a pure backup system... The panels and controllers are not cheap, and the batteries will need servicing once a month (distilled water, cleaning) and replacement every 5-10 years...

    For pure backup, a generator and fuel is difficult to beat. Up front costs are low, get propane, and the fuel will store virtually forever, and you can store enough fuel to last you a few weeks or more (assuming you have the appropriate space). Change the oil, test the genset, minor maintenance and you are done.

    If you have lots of power outages and they are long (such as ice storms), solar still may be worth it too you.

    Also, look at your loads--perhaps replacing your current pump, or adding a second solar panel+dc well pump would work for you... Use the solar pump to pump into a cistern and/or landscape watering (open flow type pumping is probably better for pure solar than pressurizing a home plumbing system) and you can avoid both the cost/nightmare of a large battery bank and use your solar pumping investment every day--and avoid much of your pumping costs.

    You could also use a small/backup solar powered pump+small battery bank to pressurize your home--for example.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Help before I buy system

    Thanks for the reply BB. I do not intend to use this system at 7kw, just wanted to have inverter that produces 220v and room to expand later. I am just getting started and will expand later to add more current usage. I will print your response and study it to fully understand.
  • BB.BB. Super Moderators, Administrators Posts: 31,918 admin
    Re: Help before I buy system

    You will probably also look at the MSW (Modified Square Wave inverter) vs a True Sine Wave (TSW) inverter.

    Typically, you will not be able to ground an MSW inverter's AC output (which is generally done with US 120/240 VAC power) if the MSW DC input is also grounded (unless you use an isolation transformer) which is typically done for safety and lightning protection for DC off-grid systems.

    If you use an AC transfer switch so that your well pump's AC is floating (and not ground referenced in the pump itself)--you should be OK with an MSW inverter.

    There are other issues with motors (and some other appliances too) and MSW inverters--the Modified Square Wave can cause motors to use roughly 20% more power (wasted as heat) and can confuse timing circuits (mechanical clocks) and cause some AC devices to fail (probably 90% of AC devices will work fine on MSW, and 10% may fail--and it is difficult to know which will work and which will fail before hand).

    Our host (NAWS) has many FAQ's in their website under major topics (panels, charge controllers, inverters, etc.)... Take a read through their inverter FAQ and there is a very nice Home Power Magazine article on Inverters and Well Pumps there too (both are near bottom of page)...

    -Bill

    PS, check above your last post--we posted about the same time and you may have missed my 2nd reply above yours.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 31,918 admin
    Re: Help before I buy system

    Tony,

    And I missed the 4x in front of the battery(ies)... And that they are 110 Amp*Hours, not 120 Amp*Hours...

    OM

    Oh well... The basic analysis is correct. But you have ~4x the number of batteries--so the numbers are simply x4 (roughly) for how long they will supply the loads. For a large well-pump--I would go with the 48 Volt battery bank configuration (to lower current requirements)--and I would assume that AIMS inverter is probably 24 or 48 volt input too (the current would be huge if it was a 12 volt inverter).

    I can fix the post if it is too confusing (which would be confusing too--if you already are studying it).

    -Bill

    Hmmm... no excuses for me (not on any pain meds--or meds otherwise). ;)
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Help before I buy system

    I just found out the companies I was looking at for the batteries and solar cell are in Calif. and the cost of shipping to Ga. will be very high. Any suggestions for companies close to Ga.
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Help before I buy system
    BB. wrote: »
    Tony,

    And I missed the 4x in front of the battery(ies)... And that they are 110 Amp*Hours, not 120 Amp*Hours...

    OM

    Oh well... The basic analysis is correct. But you have ~4x the number of batteries--so the numbers are simply x4 (roughly) for how long they will supply the loads. For a large well-pump--I would go with the 48 Volt battery bank configuration (to lower current requirements)--and I would assume that AIMS inverter is probably 24 or 48 volt input too (the current would be huge if it was a 12 volt inverter).

    I can fix the post if it is too confusing (which would be confusing too--if you already are studying it).

    -Bill

    Hmmm... no excuses for me (not on any pain meds--or meds otherwise). ;)


    I guess you could accuse me of: ready, fire, READ! Sorry for the confusion!

    T.

    PS. I agree that "going off grid" is real expensive. The grid is our cheapest energy source. Consider all the costs and the motivation,

    Tony
  • BB.BB. Super Moderators, Administrators Posts: 31,918 admin
    Re: Help before I buy system

    Unfortunately, boxing and shipping costs are high as soon as the parts go from stock to the loading dock (improperly packed solar panels are just a very expensive pile of broken glass--and batteries are heavy+hazardous chemical).

    If you can find a local supplier where you can pick them up locally--it will probably save you money... Also, if your orders have large numbers of solar panels--the palletizing costs, per panel, are much less.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,324 ✭✭✭✭✭
    Re: Help before I buy system
    Old Man wrote: »
    I just found out the companies I was looking at for the batteries and solar cell are in Calif. and the cost of shipping to Ga. will be very high. Any suggestions for companies close to Ga.

    Golf Cart batteries are fairly good, but I don't know how long they will last. A local golf course should be able to give you a line on their supplier. 4 heavy 12V ones will give you 48V, as well as 8 medium weight 6V batteries, still 48V total.

    PV panels - since you stated you are going to buy elsewhere, here is a site closer to you, and generally, good prices if you stick with the blems (still have full warrantys) http://www.sunelec.com/
    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 ,

  • System2System2 Posts: 6,290 admin
    Re: Help before I buy system

    Thanks for all the reply's.

    I found a battery company about 20 miles from me and will purchase from them, also found a company that will ship the solar panels for a reasonable fee. With the price they quoted I am going to go with 6 --210 w panels and 6 --110 aH batterys. Will let all know how it all works out. Will start ordering in approx. one month.
  • wild01wild01 Solar Expert Posts: 100 ✭✭✭
    Re: Help before I buy system

    Old Man,
    the first bit of advise i would give you is seriously consider replacing your well pump with a grundfos submersible sq series 110 volt. they run $500-700, and have a zero surge start. your current aims inverter choice might not push a well pump. I had 110 volt myers rustler and it would stall a 5000 watt generator. well pumps have an ungodly high surge start.
    secondly, unless you need 220 for something else, consider going with a 3-4k pure sine wave inverter. msw will run almost everything the only problem is what it won't run it destroys! and there is really only one way to find out what it wont run-plug it in.

    also if you have grid electric available to you, understand you will never save money by going off the grid. just not gonna happen. the biggest reason for off-grid power is people who don't have a cost effective way to get to the grid!!!

    also if you go through with it, consider 24 volts before 12, 36 before 24, and 48 before 36, in the long run it's better to have to much then not enough. if you upgrade past 1000 watts of solar, you will end up needing 2 mppt charge controllers w/12 volt past 2000 2 mppt charge controllers w/24 volt, not to mention the copper wiring cost. I'm to the point now where only half my system is running on my flexmax 80 cc because i went with 12 volts to save a few hundred on batteries, if I had gone 24 by now my batteries would be paid for in cc and wiring, also a 7000 watt inverter is going to require ungodly wiring sized @ 12 or 24 volts 24 volt think 4/0 12 volt think 2 4/0 cables per side, and also the bigger the load amps the bigger (and exponentially more expensive) the fuse


    ps I've had some experience with aims, the electronic noise pollution is extreme, don't plan on using a tv or radio w/o some serious interference. think 20 db buzz
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