Help with inverter size

AccountDeleted
AccountDeleted Registered Users Posts: 10 ✭✭
Hi,

I purchased this PV/turbine kit:
https://www.amazon.com/gp/product/B01NCQR64D/ref=ox_sc_sfl_title_18?ie=UTF8&psc=1&smid=A5KU5HDAPDC75

And 4 of these batteries:
EPM Products  - Seahawk  Marine heavy duty deep cycle - Model DP27
CCA @ O degrees F = 650
MCA @ 32 degrees F = 800
23 AMP AVE.
175 Min.

It is a 24V system.  I plan on running whatever I can in my house with it - not sure what yet until I understand how much power this can store and generate for the load.

How do I go about sizing the inverter?  Keep in mind that I may add a second PV/turbine kit that is the same and more batteries.

Thanks
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Comments

  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Normally we work from the loads to what you need, it appears you have jumped the gun.

    So how much wind do you get, do you know the wind profile of the win generator? You they have a diversion load for the wind generator? Maybe it just has a heat sink with the aluminum frame of the charge controller? if so when Your batteries are charged and you have strong steady wind you will have a 400 watt heater in stead of a charge controller. Since electronics and heat don't play well together, lets hope they suggest or have a diversion load, from my read it doesn't nor does it explain not having one. Not a lot of fans of small wind here.

    So you have 200 watts of solar panels on what I will assume is a pwm charge controller, they also don't give any specs on the solar panels so I'll leap to the assumption that they have a VMP of 18 which would mean they produce 18 volts under load. so that would put the amperage at about 5.5 amps. There are 2 of them so figure about 11 amps from the solar panels. in direct sunlight close (2.5 hours either side) to solar noon.

    You have purchased "Seahawk "epm products" Model DP27 battery." which a quick search returned no results, so using your numbers they appear to be great batteries to start your boat! Unfortunately we aren't trying to start a boat.

    Generally we find batteries for marine use that have cca (cold cranking amps) values published and no amp hour values to not truly be deep cycle batteries and have a poor life in a true deep cycle use. If you can return them I would. Best value would be golf cart batteries, which are true deep cycle batteries and mass produced which keeps the cost down. I'll use this Group 27 marine battery from Sam's club for it's rating, they claim 90 amphours at a 20 hour rate.

    https://www.samsclub.com/sams/duracell-marine-battery-group-size-27dc/prod3590231.ip

    So you would have 2 in series, in series the voltage adds and the amperage remains the same, so each string would have 24 volts at 90 amps. Then you would have 2 strings in parallel, In parallel the voltage remains the same and the amperage adds, so you would end up with a 180 amp hour battery bank at 24 volts.

    Typically a flooded lead acid battery will want a charging rate of about 10-13% so 18-23 amps, so depending on how much  wind you get you may or may not have enough charging capacity for your battery bank.

    Assuming you have enough energy to charge your battery bank, we typically would like to use only the top 20% each day during relatively normal days. so you have about 36 amp hours at 24 volts to use. To convert that to watts, you can use this formula, amps x volts = watts, so you have 36 amp hours at 24 volts = 864 watt hours. Most inverters will lose about 15% of the energy converting Dc to AC so you would have about 864x85%=@735 watt hours, This will run a modern 55 inch TV setup for minimal usage for about 9 hours at 80 watts, so a small invert would work fine. Small chest freezer will use about this amount of watts during a 24 hour day, but running at around 100 watts and turning on and off during the day. Because it is starting a compressor, it will require a much larger amount of current for a brief time starting the motor. So likely you would need a 800-1000 watt inverter. So much depends on how you would like to use the energy.

    There are 2 types of inverters, pure sine and modified sine. If you want to run sensitive electronics like a TV of desktop computer, or any thing with a motor, like a fridge! you are better off with a true sine wave inverter. If you want to run a pure resistance load like an old incandescent light bulb or a toaster, or non sensitive electronics, usually something with a rechargeable battery which will buffer the energy, Laptop or cell phone. a modified sine wave will work fine.

    Hope this helps!




    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    To add to Photowhit's information... I like to call the battery bank the "heart" of your system. Normally, one defines the loads, then defines the battery bank..
    • 24 volts * 90 Amp*Hours * 0.85 AC inverter eff * 1/2 days of storage * 0.50 maximum discharge (longer battery life) = 459 WH per day for 2 days AC loads
     Nominally, we want 5% to 13% rate of charge with solar--5% good for emergency backup, weekend/seasonal cabin use. 10%+ rate of charge recommended for full time off grid power:
    • 90 AH * 29.0 volts charging * 1/0.77 solar panel+controller deratings * 0.05 rate of charge = 169 Watt array minimum
    • 90 AH * 29.0 volts charging * 1/0.77 solar panel+controller deratings * 0.10 rate of charge = 339 Watt array nominal
    • 90 AH * 29.0 volts charging * 1/0.77 solar panel+controller deratings * 0.13 rate of charge = 441 Watt array cost effective maximum
    Your 2x 100 Watt solar panels are just over 5% rate of charge--So you do not want to have this run loads every day--The battery bank will probably not be properly recharged for full time off grid usage.

    Next, how much energy per day would you get from solar. Assuming a fixed array somewhere around Philadelphia PA:
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Philadelphia
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 50° angle:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    3.07
     
    3.77
     
    4.23
     
    4.46
     
    4.74
     
    4.84
     
    Jul Aug Sep Oct Nov Dec
    4.95
     
    4.79
     
    4.55
     
    4.21
     
    3.12
     
    2.77
     
    Toss the bottom three months of winter (assuming use backup genset), February at 3.77 hours of sun per day (long term average):
    • 200 Watts panels * 0.52 off grid solar AC system end to end efficiency * 3.77 hours of sun (Feb break even month) = 392 WH per day average February sun
    How big of AC inverter? Note that 392 WH per day is not a lot of power--Run some LED lighting, charge a cell phone+tablet, a few hours of laptop recharging/use.

    If you want to run 5 hours of AC power per evening--That would be around:
    • 392 Watt*Hours / 5 hours a night = 78 Watt average AC load
    For a 90 AH @ 24 VDC flooded cell lead acid battery bank--We expect:
    • 90 AH * 24 VDC * 0.85 AC inverter eff * 1/8 hour discharge rate =  ~230 Watt AC typical maximum AC inverter (continuous discharge rate)
    • 90 AH * 24 VDC * 0.85 AC inverter eff * 1/5 hour discharge rate = 367 Watt AC maximum supportable (reliably) AC inverter
    Regarding the Wind Turbine--I am not a big fan of small wind turbines. You have to have them mounted pretty high in the air (and above local homes/trees/etc.) to get Laminar Flow prevailing winds. A wind turbine in turbulent/rolling air is just about useless. In most built up/forested areas, that means a tower 30-60+ feet tall minimum (that is not an insignificant size tower).

    If you expect/hope to get "useful" amount of energy from the wind turbine portion--You probably want to look around for how to site and mount a wind turbine:

    Wind Power Links
    www.otherpower.com (good forum for DIY Wind Power)
    Hugh Piggott - Scoraig Wind Electric site for tons of info (from mike90045)
    Scoraig Wind "Recipe Book" for DYI Turbines (from Chris Olson... From his 4/11/2013 post)
    www.greenpowertalk.org (added from "russ"--Like here but more wind/less solar)
    Small windpower a scam ? Survey says SO
    Truth About Skystream & SWWP
    Windmax HY-2000 2kW Wind Turbine

    Note, I did not predict how much power your turbine will produce--At best (good siting, good winds, higher tower), you might get 10-15% of nameplate capacity. A 400 Watt turbine with 10% capacity:
    • 400 Watts * 10% of capacity * 24 hours = 960 WH per day
    Or, very roughly, a bit more energy as 4x 100 Watt solar panels (estimated ~784 WH per day February average). Lot easier and cheaper than flying a turbine 30-60 feet in the air--And sun is usually more predictable than wind.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • AccountDeleted
    AccountDeleted Registered Users Posts: 10 ✭✭
    Thanks for the information.  

    I understand that normally one defines the loads.  I don't have any defined load and won't have a defined load.  I want to use all of the power I can produce with this system and then figure out what I can put on the load.  For my purposes, it doesn't make sense to define a load when I have a limited amount of hardware and am not going to add any more yet. 

    My goals:
    To learn from this by doing and setting it up and running it.  
    To store any amount of power I can, over as many days as it takes, into the bank of 4 batteries.  It does not matter to me if it takes a week to charge them to capacity.  The goal is to store something and to have it to use daily at a certain rate or in case of power outtage, to have a little for electronics or whatever I can power (fridge, freezer, lights, whatever it can handle).

    My batteries are deep cycle not starting batteries as the first poster suggested.  They look exactly like the duracell batteries in the link - probably the same maker since they look exactly alike.  Maybe the same battery.

    I don't have any goals regarding how much is produced in a day or how much load I can handle.  I'm going to mount the panels and turbine and let it charge the battery bank and see what I can power for how long.  

    The kit came with a controller box.  So this will control the charge level to the bank and stop the charge when the bank is full.  I have wired the bank of 4 batteries so that it is set up for 24v and verified 24v on the volt meter.  

    I've wired the 2 panels together so that they are 24 instead of 12.  And verified that the output is correct.

    The turbine is 24v so that is ready to go.  It has it's own 3 wire connection to the controller so that is good also.  I understand that good wind is up high.  I am on top of a huge hill and have very strong winds in one direction on the top of my roof very often, only a few feet above the roof.  So this thing is going to spin.  I don't really care how much I get from it, just want that wind to be captured into any amount of power and I'll be a happy guy.  Learning is the key here for me and to capture some power along the way.

    I am all set to go, just need to buy an inverter.  

    I'm just trying to figure out what size inverter will handle the bank of 4 batteries at capacity and how many watts I can expect to support to a load at maximum wattage that can be supported by the bank.  

    So all of the calculations about how much it all may produce are very interesting but not really what I'm looking for.  I would like to know how to calculate the inverter size necessary for my bank of 4 batteries 24v when they are charged to capacity.  This way, even if it takes several days to charge up completely, I'll have the proper inverter to handle it when I need it.

    Thanks for your help.
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Your marine batteries can say Deep Cycle and not be true deep cycle. That's just the way it works out. Usually if it has a CCA rating but not a amp hour rating they won't be... They will often be 'dual purpose' Usually doesn't work well for daily cycling.
    Sorry you don't believe me, only been on the solar forums and BB's for 20 years now... I truly hope they are!

    Since you can't tell us what you will want to run, I did try to get an idea so we would know what wattage an inverter you would need, I've tried to give you the information you need to make a choice, so did Bill!

    You have about 1Kwh of usable energy each sunny day to stay within 30% of full, That's 1000 watt hours, you can use this up running a 300 watt inverter at max capacity for 3 hours (900 watts hours in 3 hours + the inverters use) or a 3000 watt inverter in about 15 minutes (with voltage sag). YOU need to figure out what wattage items you want to run.


    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    So all of the calculations about how much it all may produce are very interesting but not really what I'm looking for.  I would like to know how to calculate the inverter size necessary for my bank of 4 batteries 24v when they are charged to capacity.  This way, even if it takes several days to charge up completely, I'll have the proper inverter to handle it when I need it.
    Off grid,  Battery based, solar is very hands on, suggest if you don't want to learn the concepts, you sell the equipment now and save the grief! seriously! I don't care if you don't want to reread my drivel, but try to read and understand the concepts Bill has presented, it will allow you to use solar effectively.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • AccountDeleted
    AccountDeleted Registered Users Posts: 10 ✭✭
    The batteries are not dual purpose.  I know about those.  This brand has the two different types.  I bought the deep cycle marine ones.  This really has nothing to do with your 20 years of experience or whether I believe you or not.  I'm not sure why you are pushing this thought so much or why some company would sell batteries that are labeled incorrectly.  But this company sells the two types and I got the deep cycle ones.  Sounds like you are really proud of your 20 years of experience and your ego is pushing this idea that you are right and I'm wrong.  Whatever.  This kind of behavior is common on all types of forums where experienced people are and it is annoying to beginners since we recieve this attitude where it comes off as "you are stupid and I am smart", which is exactly what is happening here.  Instead of answering the question, there are lots of facts and figures and a show of how much you know.  Meanwhile the simple question is still left without a simple answer.  Rather a very complicated answer is given to show that "you know more and the beginner is stupid".  

    Simple answer is what you have now given.  300-3000 watt inverter.  But still, the answer is incomplete because you are basing everything on how much can be produced which really has nothing to do with my question and I even clarified that saying that it doesn't matter how many days it takes to charge my bank - I just want to know what size inverter makes sense for my bank of 4 batteries fully charged (no matter how they got that way).  Forget that there are even panels and a turbine - you are getting all wrapped up in the charging and distracted by the details of how much can be produced.  Isolate the bank in your mind.  The bank could have been charged with a trickle charger and then the power goes out from a storm.  Does not matter what charged that bank or how long it will take to charge again.  Only matters what is the max watts that bank can power something/anything.  I am asking what is the largest wattage inverter I would need to support the bank I have and how many hours it could run on a certain wattage.  Each time I get an answer it has something to do with how much is produced each day, how someone is not a fan of small turbines, or how my batteries are the wrong type and I'm stupid.   And lots of theory and calculations about how much may be produced on some sunny day.  All of which I don't care about.  Just care how many watts I can produce from this bank of batteries for how long if it is fully charged.  Is it possible to give a simple answer to this?  If not why?


  • AccountDeleted
    AccountDeleted Registered Users Posts: 10 ✭✭
    Photowhit said:
    So all of the calculations about how much it all may produce are very interesting but not really what I'm looking for.  I would like to know how to calculate the inverter size necessary for my bank of 4 batteries 24v when they are charged to capacity.  This way, even if it takes several days to charge up completely, I'll have the proper inverter to handle it when I need it.
    Off grid,  Battery based, solar is very hands on, suggest if you don't want to learn the concepts, you sell the equipment now and save the grief! seriously! I don't care if you don't want to reread my drivel, but try to read and understand the concepts Bill has presented, it will allow you to use solar effectively.
    I don't need to do any calculations.  I'm going to drain my batteries and then charge them back up as long as it takes to get to full capacity, then run stuff and do the "hands on" thing you talk about and actually see how long I can power things rather than calculate something on paper.  There is no grief involved and I don't need to sell anything.  Again your ego is getting in the way.  I don't want any more answers or ego from you.
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    I did my calculation of the available capacity of your battery bank based on the information I went out and got. Sorry your reading comprehension should get in your way of learning.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • AccountDeleted
    AccountDeleted Registered Users Posts: 10 ✭✭
    now your ego has turned to more insults.  still no basic complete recommendation and answer.  Insults do not make you smarter, just an a h.
  • AccountDeleted
    AccountDeleted Registered Users Posts: 10 ✭✭
    Its really much easier than all that you are saying.  You charge batteries with panels and wind and then use the power later.  Hook up a controller and an inverter of the right size and see how long you can power things.  If you use up the power too quickly the first time, run less things on the bank next time.  No need for complicated calculations.  Its so simple almost anyone could do it.  Your 20 years has really not helped much if you can't give a simple answer.  And if you are one of the main gurus of this site I have no interest in it anymore for sure.  You can't get past your self to give a simple answer and are more focused on proving you know more and that "it's more complicated you should go home".  Well, I will.  See ya later photowhit.  I'll do some more doing and no calculations and figure out what I need.  I do no one thing.  I don't need you or anyone like you.
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Sorry, I've given you a comprehensive answer.  If you want a "Buy this" answer any sales person will give you one! Bill has also given you a good answer.

    Perhaps this will help others understand that the inverter size depends on the load you want to run.

    Best of luck to you. Maybe you will run into "Sunking" on another forum, I might have to monitor that interaction! It would be fun!

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • AccountDeleted
    AccountDeleted Registered Users Posts: 10 ✭✭
    I don't want a comprehensive answer.  As I stated I want an opinion on what inverter to buy, not a buy this button or a sales person smarty pants.  Just a short brief recommendation based upon the bank not load or power production.  You still don't get it. 

    I don't know what "sunking" is or how I would run into it on another forum or how that would be fun.  Again a weird answer from you instaead of a simple recommendation with a simple explanation.  

    Can you please tell me all of the other forums you are a part of so I can avoid them all?

    Thanks
  • AccountDeleted
    AccountDeleted Registered Users Posts: 10 ✭✭
    Better yet, I'll just avoid all forums.  I suspect that they are all trolled by people like you who get into all of the details and miss the simple question that deserves a simple answer due to enflated egos.
  • AccountDeleted
    AccountDeleted Registered Users Posts: 10 ✭✭
    its easy to answer my question not hard

  • myocardia
    myocardia Solar Expert Posts: 118 ✭✭✭
    edited October 2017 #16
    @BB You should really, really, really sticky this thread at the top of this same subforum, as how not to act on a public forum, when you don't have the slightest idea what you're talking about.

    edit: Oh, I forgot to add that B.B., Photowit and myself belong to every solar forum on the planet, just with different usernames. See you at the next one. :'(
    DoD= depth of discharge= amount removed from that battery   SoC= state of charge= amount remaining in that battery
    So, 0% DoD= 100% SoC, 25% DoD= 75% SoC, 50% DoD= 50% SoC, 75% DoD= 25% SoC, 100% DoD= 0% SoC
    A/C= air conditioning AC= alternating current (what comes from the outlets in your home) DC= direct current (what batteries & solar panels use)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Well, I tried. In my earlier post:
    If you want to run 5 hours of AC power per evening--That would be around:
    • 392 Watt*Hours / 5 hours a night = 78 Watt average AC load
    For a 90 AH @ 24 VDC flooded cell lead acid battery bank--We expect:
    • 90 AH * 24 VDC * 0.85 AC inverter eff * 1/8 hour discharge rate =  ~230 Watt AC typical maximum AC inverter (continuous discharge rate)
    • 90 AH * 24 VDC * 0.85 AC inverter eff * 1/5 hour discharge rate = 367 Watt AC maximum supportable (reliably) AC inverter

    I am not going to sticky this thread--Everybody has bad days and we don't need to make a scarlet letter out of it when it happens.

    The account has been "deleted".

    -Bill


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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