Please: Haiti Off Grid System advice and constructive feedback needed

DarkstormNH
DarkstormNH Registered Users Posts: 48 ✭✭
edited October 2015 in Solar Beginners Corner #1

I currently have 8 6 volts battery (trojan t105) a magnum 2000 watts pure sine wave inverter setup at 12 volts.

I would like to upgrade to 48 volts or if convinced by the expert 24 volts. 
the load a fridge 1.02kwh/24h 
a freezer .900 kwh/24h 
A  55' television  90 watts usage 5-6 hours
A 32 ' television  60 watts usage 4 hours per day
1 fan 40wx3 hours=120
lights total 450 wh
misc 500wh

Total looks like 3450 wh per day I would like to add some fudge room and say 4k per day
on the generation 4 250 watts panel by 5.5 hours per day 4/5.5=728 watts 
if that is ok how should i connect i them n series or series parallel

the inverter I was thinking on buying a 24 or 48 volts same price magnum pae version

charge controller I plan on an mppt version for sure what is the minimum I can get away with 60 amps 80 amps and so on.

Please help with clear directions

Thanks

Comments

  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    charge controller I plan on an mppt version for sure what is the minimum I can get away with 60 amps 80 amps and so on.

    Please help with clear directions

    The size (capacity) of the controller is determined by the battery voltage (which is 48 volts) and the size of your solar array (which you have not told us). 

    Hopefully you have enough panels for the size of your battery.  btw, your battery bank looks a bit small to support 3.5 kwh per day of consumption.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    4kWh is still in the realm of 24V systems, however if you ever plan to grow this, then 48V will save you yet another step up.  For system sizing find one of Bills recent posts and follow his math through.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    OK--A quick set of calculations for your system... As folks say, you probably should be looking at 48 volt battery bank system:
    • 4,000 WH * 1/0.85 AC inverter eff * 2 days of storage * 1/0.50 maximum discharge * 1/48 volt battery bank = 392 AH @ 48 volt battery bank
    If you do not plan on going >4kWH per day in the future, then a 24 volt battery bank would be ~784 AH @ 24 volts--My humble suggestion is to keep your battery bank below ~800 AH if possible--Copper wiring gets very heavy to manage the higher current level and the lower voltages.

    Next, to charge your battery bank, 5% to 13% rate of charge works pretty well for solar... 5% can be OK for weekend/seasonal (not winter) use... 10% or more is suggested for a full time off grid home (9+ months) and/or if you have large daytime loads (work, irrigation, computers, etc.).
    • 392 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 1,502 Watt array minimum
    • 392 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 3,004 Watt array nominal
    • 392 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 3,905 Watt array "cost effective" maximum
    So, as you can see, the size of your battery bank does affect the size of the array.

    And, there is the amount of energy that you can collect from your solar array... A guess at Derry Village, NH, using SolarElectric handbook:

    http://solarelectricityhandbook.com/solar-irradiance.html

    Derry Village
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 47° angle (from vertical:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    3.27
     
    3.95
     
    4.47
     
    4.61
     
    4.76
     
    4.81
     
    Jul Aug Sep Oct Nov Dec
    5.07
     
    4.93
     
    4.70
     
    4.13
     
    3.17
     
    2.94
     
    If I am half way correct--You do not get near 5.5 hours of sun per day even in summer (if you have a two axis tracker, you can collect more sun).

    If full time living, toss the bottom three months (assume you use a genset to make up power during bad weather), then Jan @ 3.27 Hours of sun minimum with a 4kWH per day:
    • 4,000 WH per day * 1/0.52 end to end off grid system eff * 1/3.27 hours minimum sun = 2,352 Watt array minimum (break even January)
    Anyway--That is my guess at how the math may play out--Your thoughts?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • DarkstormNH
    DarkstormNH Registered Users Posts: 48 ✭✭
    BB. said:
    OK--A quick set of calculations for your system... As folks say, you probably should be looking at 48 volt battery bank system:
    • 4,000 WH * 1/0.85 AC inverter eff * 2 days of storage * 1/0.50 maximum discharge * 1/48 volt battery bank = 392 AH @ 48 volt battery bank
    BB: Thank you for the reply great meat (substance) in the post I need to provide further clarification
    8 6 volts in series would that be 225 AH or 392 I cant see where the 392 come from sorry
    If you do not plan on going >4kWH per day in the future, then a 24 volt battery bank would be ~784 AH @ 24 volts--My humble suggestion is to keep your battery bank below ~800 AH if possible--Copper wiring gets very heavy to manage the higher current level and the lower voltages.

    BB: I respect your opinion and I agree I will go straight to 48 volts

    Next, to charge your battery bank, 5% to 13% rate of charge works pretty well for solar... 5% can be OK for weekend/seasonal (not winter) use... 10% or more is suggested for a full time off grid home (9+ months) and/or if you have large daytime loads (work, irrigation, computers, etc.).
    • 392 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 1,502 Watt array minimum
    BB: can i come in at the minimum and expand to the nominal? what min charge controller would be recommended?
    • 392 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 3,004 Watt array nominal
    • 392 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 3,905 Watt array "cost effective" maximum
    So, as you can see, the size of your battery bank does affect the size of the array.

    And, there is the amount of energy that you can collect from your solar array... A guess at Derry Village, NH, using SolarElectric handbook:

    http://solarelectricityhandbook.com/solar-irradiance.html

    BB: sorry the system will be in Haiti I went to the link you provided here's what I got
    I await further feedback

    Thanks

    Petionville
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 72° angle:
    (For best year-round performance)

    JanFebMarAprMayJun
    5.58
     
    5.73
     
    5.69
     
    5.69
     
    5.63
     
    6.26
     
    JulAugSepOctNovDec
    6.26
     
    5.77
     
    5.44
     
    5.22
     
    5.13
     
    5.29
     

    Derry Village
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 47° angle (from vertical:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    3.27
     
    3.95
     
    4.47
     
    4.61
     
    4.76
     
    4.81
     
    Jul Aug Sep Oct Nov Dec
    5.07
     
    4.93
     
    4.70
     
    4.13
     
    3.17
     
    2.94
     
    If I am half way correct--You do not get near 5.5 hours of sun per day even in summer (if you have a two axis tracker, you can collect more sun).

    If full time living, toss the bottom three months (assume you use a genset to make up power during bad weather), then Jan @ 3.27 Hours of sun minimum with a 4kWH per day:
    • 4,000 WH per day * 1/0.52 end to end off grid system eff * 1/3.27 hours minimum sun = 2,352 Watt array minimum (break even January)
    Anyway--That is my guess at how the math may play out--Your thoughts?

    -Bill

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    225 AH supplying 4,000 WH per day is a bit on the small size... You would be deep cycling the battery bank pretty close to 50% after just one day of "no sun"... However, if much of your loads are during the day time, a 225 AH @ 48 volt battery bank may work OK for you (and/or if you cut back on energy usage on dark days).

    You can take my equation and use ~1 to 3 days of storage and 50% maximum discharge. Over the years, 2 days of storage and 50% maximum discharge seems to be an sweet point for most off grid power systems. I am all for balanced system design. Battery bank sized to loads (storage and peak power needs). Then size the solar/charge controllers to keep the battery bank happy.

    For RV systems, generally they have a weight/battery size limit--And they may design for 1 day of storage. For off grid homes, you can fit a larger battery bank--But a 3 day storage means a very large/expensive battery bank and a larger solar array to meet minimum charging requirements--Generally not recommended for the average home.

    The 392 AH @ 48 volts (or ~784 AH @ 24 volts) is the result of 4kW of AC power, 2 days of storage, and 50% maximum discharge.

    It is very difficult to "enlarge" an off grid power system... Many times need a new AC inverter (24 to 48 volt change), new battery bank/configuration, new/larger charge controllers, etc... Suggest that you nail your power needs (and really work on conservation--your best bang for the buck) first--Then design a system that supports those needs.

    If you do not know your power needs just yet... Run a (borrowed, rented, pre-bought backup genset) generator for 1-4 weeks with a Watt*Hour meter to log your power usage.

    4kWH per day can run a full sized Energy Star refrigerator, lights, TV/Laptop computer, washing machine, well pump in a "near normal" electrical existence--Albeit with serious energy conservation for an off grid home.

    Next, 24 or 48 volt battery bank... Either would work OK for 225 @ 48 volts or 450 AH @ 24 volts (same amount of total energy storage: Power=Volts*Current(or AH) is the same in either case).

    Sizing the battery bank also limits the maximum (practical) size of the GT inverter... A 225 AH @ 48 volt battery bank (or a 450 AH @ 24 volts) would "reliably' support about a 2.25 kWatt (2,250 Watt) maximum continuous rated AC inverter.

    Look at your inverter options (and peak power requirements) to see if the 225 AH @ 48 volt battery bank is "big enough" for your peak power needs.

    Note as AC inverter move up to higher rated voltages, it can be more difficult to find the smaller rated inverters. In your case, you may not find a ~2,000 Watt @ 48 volt inverter, but can find a 24 volt version closer to your needs.

    And larger inverter typically have higher "Tare Losses" (lost power just from being "turned on" 24 hours per day). Another reason to not "over size" your AC inverter if you don't need it..

    Note, the above answers are based on rules of thumbs that we have used for many years here on the forum. While they generally give a good/reliable system that meets people's needs, your power needs may be different--Make sure you understand the basic math/assumptions being made--And if your usage is different, we will need to figure out a different solution for you.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    And system will be in Haiti... OK, that gives you a bit more daily sun :D

    We have a few people here that have built systems in Haiti. You want to have a "bullet proof system" (as best you can), and not oversize it--There will probably be sometime when somebody makes and "oops" and kills the battery bank (taking a lead acid battery bank "dead" or ~10.5 volts per 12 volt battery). The batteries will either not recover, or have a very short life left (weeks/months typically).

    My two cents:
    • Keep battery bank as small as practical (2 days and 50% maximum discharge is good)
    • Give them one (or two) good quality hydrometers and a note book to track specific gravity
    • A "cheaper" DC Current Clamp DMM (again, maybe 2, one for a spare)
    • If you can justify the costs, a Battery Monitor can be helpful. A true current shunt battery monitor is nice (but are complex gear and can be miss-programmed and/or drift and give confusing/wrong answers at times). A voltage based battery monitor may work "good enough" to keep people from killing the bank.
    • Make sure distilled or deionized water is available, or at the very least, clean/filtered rainwater is used to top off batteries.
    http://www.solar-electric.com/batteries-meters-accessories/metersmonitors/tr20mosy.html (current shunt based)
    http://www.solar-electric.com/batteries-meters-accessories/metersmonitors/mnbcm.html (voltage based)
    http://smartgauge.co.uk/smartgauge.html (voltage based)

    Expanding the system--Mixing old and new batteries together can be a pain... If you have more than a year on the existing batteries (and/or the first bank has been "stressed") you now end up with a bank where 1/2 the batteries will fail in 2-4 years (debugging/replacing), then a a few years later the next 1/2 age/cycle out.

    It can be difficult to keep everything running normally--When you put in a 1/2 old 1/2 new battery bank--Just throws more confusion/maintenance into the mix--And you may not have dedicated person there that can maintain the system for you, reliably.

    For controllers, Midnite, Outback, MorningStar, and Schneider are all good places to start with larger MPPT charge controllers (typically 60-80+ amp rated charging current)--Try to nail down the rest of system sizing (and how far the solar array will be from the charge controller/battery shed).

    Also, look at what is available locally--Local parts and support helps the local economy and may save you expensive shipping and delays when dealing with system issues.

    Hopefully, one of the Haiti installation folks here can chime in with their suggestions.

    Plug this search string into Google and look through the results to read older threads here (the "site:" tag limits searches to this website):
    • site:forum.solar-electric.com Haiti solar system
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    One other note--The solarelectrichandbook uses 72 degree tilt from vertical. Most other tools use tilt from horizontal--So be sure the array is mounted correctly (18 degrees from horizontal--Suggest a minimum of 5 degrees from horizontal so the array "self cleans" during rains).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • DarkstormNH
    DarkstormNH Registered Users Posts: 48 ✭✭
    vtmaps said:
    charge controller I plan on an mppt version for sure what is the minimum I can get away with 60 amps 80 amps and so on.

    Please help with clear directions

    The size (capacity) of the controller is determined by the battery voltage (which is 48 volts) and the size of your solar array (which you have not told us). 

    Hopefully you have enough panels for the size of your battery.  btw, your battery bank looks a bit small to support 3.5 kwh per day of consumption.

    --vtMaps

  • DarkstormNH
    DarkstormNH Registered Users Posts: 48 ✭✭
    vtmaps said:
    charge controller I plan on an mppt version for sure what is the minimum I can get away with 60 amps 80 amps and so on.

    Please help with clear directions

    The size (capacity) of the controller is determined by the battery voltage (which is 48 volts) and the size of your solar array (which you have not told us). 

    Hopefully you have enough panels for the size of your battery.  btw, your battery bank looks a bit small to support 3.5 kwh per day of consumption.

    --vtMaps

    vtmaps said:
    charge controller I plan on an mppt version for sure what is the minimum I can get away with 60 amps 80 amps and so on.

    Please help with clear directions

    The size (capacity) of the controller is determined by the battery voltage (which is 48 volts) and the size of your solar array (which you have not told us). 

    Hopefully you have enough panels for the size of your battery.  btw, your battery bank looks a bit small to support 3.5 kwh per day of consumption.

    --vtMaps

    Thanks for the feedback I was thinking starting with 4 250 or 300 watts panel and adding to it later.
    my thought was I could genarate about 4-5k a day with that, keeping my usage to around 3500.
    was hping I could survive with that setup for a few, as far as the cc people seems to migrate toward the outback
    I guess I will do the same going with thw 60-0r 80
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,728 ✭✭✭✭✭✭
    edited October 2015 #11
    One of the reasons not mentioned that I like 24 V in your application is battery cost on a budget. It is far cheaper to start with a 400AH battery at 24V and then if you need more storage go up to a 24V, 1,100 AH battery. I do this all the time for people in your neck of the woods. The cost of an extra charge controller is not that great compared to the batteries and it does give you a spare if one fails. The large bank here will give you around 10 KWH and run alot of common 24V appliances without inversion loss or if the inverter has failed.

    Remember please, one day you will have to replace the bank and that cost is something you always have to have a check for!

    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

  • DarkstormNH
    DarkstormNH Registered Users Posts: 48 ✭✭
    One of the reasons not mentioned that I like 24 V in your application is battery cost on a budget. It is far cheaper to start with a 400AH battery at 24V and then if you need more storage go up to a 24V, 1,100 AH battery. I do this all the time for people in your neck of the woods. The cost of an extra charge controller is not that great compared to the batteries and it does give you a spare if one fails. The large bank here will give you around 10 KWH and run alot of common 24V appliances without inversion loss or if the inverter has failed.

    Remember please, one day you will have to replace the bank and that cost is something you always have to have a check for!

    Dave Thank you for the post,

    Please expand on your thoughts the draw back if you ever need to go up to 48 volts you will have to dump another inverter.
    I see your point on the 24 volts battery bank, as I have the issue now I have 8 6 volts trojan, I was advise it might not be enough for a 48 volts inverter, so I leaning on 24 volts now what make and brand on cc you used in haiti and why?
    can you provide some feedback on the solar panels how many you got away with?
    I 'm thinking of starting with 4 250volts panel connected in series paralel

    thanks



  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Detail do matter here... If you plan on using 4x 250 Watt panels, you need to look at their Vmp rating...

    Typically, they are around 30 volts Vmp... To charge a 24 volt battery bank, you need 2x in series for Vmp-array~60 volts (minimum of Vmp-array~35 volts to charge a 24 volt battery bank)..

    If you want to run a 48 volt bank, you need 3x minimum in series for Vmp-array~90 volts. (minimum Vmp-array~70 volts for 48 volt battery bank).

    Depending on how cold it gets in the area, you may be limited to Vmp-array of 3 panels in series. 4 panels in series is too high of Voc-cold (even if it only gets down to 60F/16C in cold weather, Voc-cold~150 VDC--Too high for an Outback MPPT controller).

    So--If you do not want to be limited to 3/6//9/etc. panels in series/parallel as would be required for an Outback+48 volt battery bank... Then going to a 24 volt with 2/4/6/8/etc. series/parallel may give you the 4 panel start you are looking for (again, need to look at the exact ratings of the solar panels you plan on using).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    One of the reasons not mentioned that I like 24 V in your application is battery cost on a budget. It is far cheaper to start with a 400AH battery at 24V and then if you need more storage go up to a 24V, 1,100 AH battery.

    Please expand on your thoughts the draw back if you ever need to go up to 48 volts you will have to dump another inverter.
    I see your point on the 24 volts battery bank, as I have the issue now I have 8 6 volts trojan, I was advise it might not be enough for a 48 volts inverter, so I leaning on 24 volts now what make and brand on cc you used in haiti and why?
    can you provide some feedback on the solar panels how many you got away with?
    I 'm thinking of starting with 4 250volts panel connected in series paralel
    I see no problem with putting your 8 trojans in a 48 volt configuration.  If you decide you want to upgrade your battery bank in the future you could nearly double it by using 8 L-16 batteries.

    As far as the controller is concerned, any of the major name brand MPPT controllers will be adequate.  If you go with 48 volt system you can get by with a smaller controller (30-45 amps output), rather than the 60 - 80 amp controller you will need with a 24 volt system.

    As far as starting with four 250 watt panels, your array size depends on your battery size and your daily energy consumption.  I already mentioned that your battery size is a bit small for your desired consumption.  I also think that a 1000 watt array is a bit small for that battery size.   By the way, the decision to go 24 vs 48 volts with those batteries does not affect the size of the array needed.... the batteries have the same storage capacity either way.

    One more thing... if you go with 48 volts, you will need to configure the panels in a string length of 3.  That means you will need 3 or 6 or 9 panels.   In my opinion, you need at least 6 panels (at either 24 or 48 volts). 

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • DarkstormNH
    DarkstormNH Registered Users Posts: 48 ✭✭

    BB. said:
    OK--A quick set of calculations for your system... As folks say, you probably should be looking at 48 volt battery bank system:
    • 4,000 WH * 1/0.85 AC inverter eff * 2 days of storage * 1/0.50 maximum discharge * 1/48 volt battery bank = 392 AH @ 48 volt battery bank
    If you do not plan on going >4kWH per day in the future, then a 24 volt battery bank would be ~784 AH @ 24 volts--My humble suggestion is to keep your battery bank below ~800 AH if possible--Copper wiring gets very heavy to manage the higher current level and the lower voltages.

    Next, to charge your battery bank, 5% to 13% rate of charge works pretty well for solar... 5% can be OK for weekend/seasonal (not winter) use... 10% or more is suggested for a full time off grid home (9+ months) and/or if you have large daytime loads (work, irrigation, computers, etc.).
    • 392 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 1,502 Watt array minimum
    • 392 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 3,004 Watt array nominal
    • 392 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 3,905 Watt array "cost effective" maximum
    So, as you can see, the size of your battery bank does affect the size of the array.

    And, there is the amount of energy that you can collect from your solar array... A guess at Derry Village, NH, using SolarElectric handbook:

    http://solarelectricityhandbook.com/solar-irradiance.html

    Derry Village
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 47° angle (from vertical:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    3.27
     
    3.95
     
    4.47
     
    4.61
     
    4.76
     
    4.81
     
    Jul Aug Sep Oct Nov Dec
    5.07
     
    4.93
     
    4.70
     
    4.13
     
    3.17
     
    2.94
     
    If I am half way correct--You do not get near 5.5 hours of sun per day even in summer (if you have a two axis tracker, you can collect more sun).

    If full time living, toss the bottom three months (assume you use a genset to make up power during bad weather), then Jan @ 3.27 Hours of sun minimum with a 4kWH per day:
    • 4,000 WH per day * 1/0.52 end to end off grid system eff * 1/3.27 hours minimum sun = 2,352 Watt array minimum (break even January)
    Anyway--That is my guess at how the math may play out--Your thoughts?

    -Bill
    Bill

    Good morning Im going back on your post to further understand

    ok I' m clear on the 392 ah it is for two days of use, however the solar setup is to charge it in one day of good sun.
    the inverter manual state a 94% eff. does that make a difference in the calculation?
    also do you have a book I can purchase ( one that you wrote)

    Thanks

  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,728 ✭✭✭✭✭✭
    edited October 2015 #16
    Yea Bill, where is the book?

    The OP should just re-read everything and sleep on it. He then should do this a few more times and make sure he understands.
    All of this is good advice if you understand it. Cost out the batteries "that you can get in your country" and then decide on 24 or 48 volts.

    "If you do not plan on going >4kWH per day in the future, then a 24 volt battery bank would be ~784 AH @ 24 volts--My humble suggestion is to keep your battery bank below ~800 AH if possible--Copper wiring gets very heavy to manage the higher current level and the lower voltages."

    Bill I do not get this, The wiring is going to be 4/0 for a single string of 400AH or a single string of 1,100 AH. Charge controllers are #6 or #4 for an 80amp controller.  Are you saying for parallel strings of batteries?  If so I agree and I never use parallel strings and have shipped batteries down south. Better to buy batteries locally if there are problems. Definitely good for the OP to understand the replacement cost!
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    The ~800 AH "limit" is based on a few different reasons...
    1. For a daily use system, I would suggest a 10% minimum rate of charge (solar panels are relatively cheap these days)--800 AH * 10% rate of charge = ~80 amps. If you go over 80 amps, you would need a second (not cheap) charge controller.
    2. An 800 AH flooded cell lead acid battery bank can output ~20% of AH capacity (say 800 AH) ~ 160 Amps. And can output ~40% of rated current (800 AH * 0.40) ~360 Amps... Those current levels need very heavy copper cables (NEC is more conservative than Marine typical numbers--And higher voltage battery banks can "tolerate" higher voltage drops--12 volt battery bank ~0.5 volt maximum drop at max continuous current.... 48 volt systems, ~2.0 volts is good for max continuous current voltage drop.
    3. And, lastly as Dave talks about--I am not a big fan of paralleling a number of battery strings together. A single string is really nice... 2 parallel strings can be OK... 3 parallel strings would be my suggested maximum paralleling. Servicing cells (checking water levels, keeping connections clean, 2 or 3 parallel strings should have a fuse/breaker per string--more costs/complexity). There are folks that have more than 3 parallel strings, and they are happy with their installation--And there are times when large AH cells (i.e., 2 volt, 4 volt, 6 volt) are simply not available locally. It can be the only workable solution (larger number of paralleled strings)--But make that decision with both eyes open.
    The above numbers work for "typical/balanced" system design--If you do not need high charging current, or can justify another $600 for a second ~80 amp MPPT charge controller--And/or you do not need high surge current (no AC well pump, power tools, etc.)--Then you can exceed my suggested starting points.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • DarkstormNH
    DarkstormNH Registered Users Posts: 48 ✭✭
    vtmaps said:
    One of the reasons not mentioned that I like 24 V in your application is battery cost on a budget. It is far cheaper to start with a 400AH battery at 24V and then if you need more storage go up to a 24V, 1,100 AH battery.

    Please expand on your thoughts the draw back if you ever need to go up to 48 volts you will have to dump another inverter.
    I see your point on the 24 volts battery bank, as I have the issue now I have 8 6 volts trojan, I was advise it might not be enough for a 48 volts inverter, so I leaning on 24 volts now what make and brand on cc you used in haiti and why?
    can you provide some feedback on the solar panels how many you got away with?
    I 'm thinking of starting with 4 250volts panel connected in series paralel
    I see no problem with putting your 8 trojans in a 48 volt configuration.  If you decide you want to upgrade your battery bank in the future you could nearly double it by using 8 L-16 batteries.

    As far as the controller is concerned, any of the major name brand MPPT controllers will be adequate.  If you go with 48 volt system you can get by with a smaller controller (30-45 amps output), rather than the 60 - 80 amp controller you will need with a 24 volt system.

    As far as starting with four 250 watt panels, your array size depends on your battery size and your daily energy consumption.  I already mentioned that your battery size is a bit small for your desired consumption.  I also think that a 1000 watt array is a bit small for that battery size.   By the way, the decision to go 24 vs 48 volts with those batteries does not affect the size of the array needed.... the batteries have the same storage capacity either way.

    One more thing... if you go with 48 volts, you will need to configure the panels in a string length of 3.  That means you will need 3 or 6 or 9 panels.   In my opinion, you need at least 6 panels (at either 24 or 48 volts). 

    --vtMaps
    Thank you I will plan on starting 6 panels
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    There are (at least) two "useful" places to install surge resistors... One is on the AC output of the inverter (wire the inverter to a breaker panel, put the S.A. there--Hot/Neutral and earth to case). Run earth ground to ground rod (6 AWG minimum for lightning protection). Losing the AC inverter and possibly some (or even all) of the 120/240 VAC appliances is not uncommon with a near/direct strike.

    The other would be where the solar panels enter the home (breaker/switch box on exterior wall, green wire/ground to local ground point next to wall).

    If you are not in a lightning area--The S.A. will not do much of anything useful.

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