Help! Ready to jump in and learn as I go. Will these work together for a small off grid system?

create54321
create54321 Registered Users Posts: 3
edited August 2019 in Solar Beginners Corner #1
First off, thanks for any help and advice.  Will this 24 volt setup work?
I will be given 6 of these panels from a relative -- https://na.panasonic.com/us/energy-solutions/solar/hit-panels/n325-photovoltaic-module-hitr-40mm  (connecting them in parallel).  These are 58 volts panels -- 69.7 Voc, 5.70A
I am looking to purchase two of these (two 12 volt deep cycle batteries placed in series to make a small 24 volt bank) -- https://www.solar-electric.com/battle-born-bb10012-100ah-12v-lithium-battery.html
I will be purchasing this Inverter for using most of the items below.  https://www.solar-electric.com/samlex-pure-sine-wave-inverter-pst-2000-24.html
Useage:  Off Grid, 1 bedroom shack
1. 5000 BTU window air conditioner (only when direct sun is available).
2. Crockpot
3. Small fan
4. Sirius xm radio
5  ARB 12v fridge
6  Nighttime LED lights
7  Smart Pot Mini 800 watts (Only when direct sun is available)
8  Laptop computer
9  Charging Milwaukee 18v tool batteries
No television.  No water pump.  No Microwave.
I know I should have a bigger battery bank but those lithium batteries expensive.  
Questions:
Is that charge controller gonna handle 6 of the above panels in parallel going to a 24 volt bank?
Is using those free Panasonic panels so mismatched to the components I listed, that I am better off not using them?   Should I just purchase 12v panels and go an entire 12v system? 
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Once again, thanks for any input.  This entire scheme got cooked up in my head when I found out I could have some free panels.  I see this as a good learning opportunity for an absolute novice.

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    edited August 2019 #2
    Welcome to the forum Create,
    Roughly, near what major city will the system be used, (hours of sun per day, min and Max temperatures)?
    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • create54321
    create54321 Registered Users Posts: 3
    BB. said:
    Welcome to the forum Create,

    Roughly, near what major city will the system be used, (hours of sun per day, min and Max temperatures)?

    Bill
    Thanks for responding Bill,
    The location is almost Albuquerque, New Mexico.  Just a few miles south. 
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    OK... Thank you, got enough to start.

    First, I will do a system with a standard Flooded Cell Lead Acid battery bank. The rules of thumbs work very well for initial sizing, and then we can look at your Li Ion battery and see how it fits.

    We can start with your loads, and then size the system to support those loads... Or we can start with your (for example) solar array, and size the system to "fit" those panels.

    For off grid solar power systems, you really need to be careful about picking your loads. The most efficient loads you can find, allow you to build as small as possible off grid power system (off grid power is pretty expensive, conservation is generally less costly).

    The 5,000 BTU A/C unit... There are newer "inverter" type A/C units, but may be hard to find in 5,000 BTU size. Standard refrigeration compressors (non-inverter type) have pretty high starting surge. A 5kBTU unit may draw around 4.6 amps, 5x that for starting surge = ~23 Amps @ 120 VAC or (P=V*I) = ~2,760 "Watts" (really VA, but that is another discussion). Your 2 kWatt inverter should support up to ~4,000 Watts/VA. So your A/C should work OK with your 2kw inverter (and if FLA battery, a suggested minimum of 400 AH @ 24 volt battery bank).

    Your ARB refrigerator is a 12 VDC fridge that probably takes around 2 amps running, and ~24 AH per 24 hours of running (at 12 volts). However, you are looking at a 24 VDC system... You should find a 24 VDC fridge (or 12/24 volt). You should not run a 12 volt appliance from a 24 volt battery bank (don't take power from 1/2 the batteries). You can get a 24 to 12 VDC down converter--But that adds more costs and a bit more losses.

    Hmmmm...  It looks like the ARB fridge should be 12/24 VDC (at least the compressor appears to be). And there are some web pages that mix 12 and 12/24 VDC on the same page...

    A small fan, XM Radio, etc. ... Probably 12 VDC (or 120 VAC). Again, an issue with 24 VDC battery bank (and choice of 24 to 12 vdc down converter). The laptop and tool battery charger--Probably just run from the AC inverter.

    Nighttime LEDs, you can find LED lighting that runs at >12 VDC... That would be nice unless you plan on running the AC inverter 24x7... 

    Your proposed inverter will draw about 0.8 amps @ 24 volts or ~19.2 Watts or ~461 WH per 24 hours (per day)... So, you do have some thinking to do here... The 461 WH per day is about what a standard Windows or Apple laptop will draw if running 8 hours per day (word processing, web access, etc.).

    What would be highly recommended is to get a Kill-a-Watt type meter for measuring your 120 VAC loads (estimated Watt*Hours per day) and a DC AH/WH meter to measure your DC loads (if you can--already have a DC power system to test/measure):

    https://www.amazon.com/s?k=kill+a+watt+meters
    https://www.amazon.com/s?k=dc+WH+AH+meter&ref=nb_sb_noss

    Note that (I think) you can run the 12/24 VDC refrigerator on a 12 volt system and get your Watt*Hours per day (WH per day should be about the same between 12 and 24 volt operation).

    Accurately estimating your loads is important... Watt*Hours per day (and/or Amp*Hours @ 24 VDC for your DC appliances) allows us to plan a system that meets your needs. Most people overestimate how much power/energy (Watts and Watt*Hours) their solar systems will produce and underestimate what their loads will consume.

    On to next post:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Let me show you what a "balanced" system design looks like with your 6x solar panels that you picked. A simple "rule of tumbs" cabin system using "relatively conservative" design rules.

    Assuming your Panasonic Panels are purchased at a good price to you (including shipping), these will work fine on a 12 or 24 VDC battery bus system with the MPPT controller you have picked. These panels do have a relatively high Voc/Vmp output voltage which means that they are not a great fit for use with your controller and a 48 VDC battery bus system. 1x panel in series is too low of Vmp-array for 48 volts (should be >72 Volts Vmp-std)... And 2x in series gives a Voc of ~139.4 volts Voc-std --- Voc (and Vmp) increase as panels get cold, and as these panel approach freezing, the Vmp-array-cold will be too high for the 150 Volt input MPPT controller (I have not gone into the specs for your controller at this point--But it is generally how these issues with panels and charge controllers shake out).

    As long as you do not plan on going >24 VDC battery bus for this system, you should be fine. 6x 325 Watt panels:
    • 6 * 325 Watt panels = 1,950 Watt array
    For a off grid solar power system with FLA battery system, suggest 5% to 10% to 13% to 20% rate of charge. 5% can work OK for a weekend cabin. 10%-13%+ is a better pick for a full time off grid cabin. The size battery bank supported by a 10% rate of charge would be:
    • 1,950 Watt array * 0.77 panel+controller deratings * 1/29.0 volts charging * 1/0.10 rate of charge = 518 AH @ 24 volt FLA battery bank
    For an FLA battery bank, suggest 2 days of "no sun" support, and 50% maximum discharge:
    • 518 AH * 24 volts * 0.85 AC inverter eff * 1/2 days storage * 0.50 max discharge = 2,642 WH per day average usage
    And there is the question of how much power your array will produce during the year. Assume Fixed Array facing south:
    http://solarelectricityhandbook.com/solar-irradiance.html

    Albuquerque
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 55° angle from vertical:
    (For best year-round performance)

    JanFebMarAprMayJun
    4.94
     
    5.32
     
    6.23
     
    6.58
     
    6.51
     
    6.27
     
    JulAugSepOctNovDec
    5.74
     
    5.57
     
    5.85
     
    5.81
     
    5.12
     
    4.76
     
    Typically, I suggest the lowest 3 months will probably need a genset to support your power needs during bad weather/etc... So that make "February" the "break even month' (may or may not need a genset):
    • 1,950 Watt array * 0.52 off grid AC system eff * 5.32 Hours of sun per day (Feb) = 5,394 WH per average February day
    Normally, would suggest that you plan on using ~50-65% of "predicted output" as base load (refrigerator, lights, computer, etc.) and on sunny days/summer days, use your optional loads (A/C, Fan, etc.).

    You are looking at 2x 12 volt @ 100 AH Li Ion batteries... Very roughly, the suggested maximum energy from the battery bank would be something like 20% to 90% capacity:
    • 24 volts * 100 AH * (0.90-0.20 State of Charge range) * 0.85 AC inverter eff * 1/1 day storage = 1,428 WH per day (1 day storage)
    • 24 volts * 100 AH * (0.90-0.20 State of Charge range) * 0.85 AC inverter eff * 1/2 day storage = 714 WH per day (2 day storage)
    I am not a battery engineer--And I am no expert in Li Ion batteries... But you can see that nice things with FLA batteries is that you can get a much large AH battery bank for more days of "no sun" storage (plus at 50% typical max discharge for FLA batteries, you can go down to 20% if you really need to--But you need to start recharging the next day for better battery life).

    Li Ion batteries are much more capable batteries (much better/quicker charging, high Amp output for small size, very good cycling life, etc.), but do have their limitations (100 Amp max continuous discharge, and 200 Amp for short term surge current), and these cannot be recharged below 25F.

    Anyway... Some information on what the system is capable of... The 100 AH @ 24 volt Li Ion battery--not a lot of storage vs the ~518 AH @ 24 volt Lead Acid battery bank that could be supported with your array... Of course, the small Li Ion battery bank will recharge very quickly with even limited sun. Does highlight the questions of your day time/night time energy usage vs size of battery bank.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • create54321
    create54321 Registered Users Posts: 3
    edited August 2019 #6
    Bill,
    Thanks, I'm re-reading, taking notes and learning from your response.  
    I will be spending the next week (or longer) looking over this info, digesting the highlights and working to understand the fine points. \
    This was absolutely a valuable and exciting correspondence for me -  THANK YOU!   I am really eager to pursue learning on the points you highlighted.  
    I had no idea there was a 25 degree charging limitation on lithium batteries.  I'm going to start reading up on SLA batteries and consider those. I didn't think about the mismatch between a 24v system and 12v appliances/lights.   I'm going to take a little time just to read up 48v systems -- just for the heck of it.
    Thanks again for your time. 
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    You are very welcome... Please feel free to ask more questions (you can continue in this thread).

    Take care and hope to hear from you again,
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • spacebass
    spacebass Registered Users Posts: 87 ✭✭
    edited August 2019 #8
    I am thinking of changing my system to 48 volts , I have 4 mono 24 volt panels in two series strings plugged in   parallel ,,Voc 46.04 volts Vmp 37.35 volts ,  (Imp 8.91, Isc 9.45 Pmax 38.15, efficiency 17.52%) will have 4 x 12volt 210ah deep cycle wet batteries, the high quality mppt controller has maximum input 150 volts , 60amp auto or manual select. Do I need a combiner to join the two strings ?. I currently have similar 24 volt system with two batteries and a 3000 real watt inverter this will be changed to 48 volt of course.
    I live in the tropics mostly 30' normal minimum 26'.
    Will this work ? 
    Thank You.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    edited August 2019 #9
    Still sort of starting at the middle, and working out... A 4x 12 volts @ 210 AH is still only "good" (recommended) for a 2,000 Watt AC inverter (with FLA batteries).

    And 3x Imp~37 volt Vmp panels in series are getting close to too high of Voc-array-cold (if will be in freezing climate) for a ~150 VDC Max input MPPT charge controller. If in a warm climate (island/tropics/etc.) may work OK.

    Some charge controller manufacturers make a program (aka string sizing tool) to help make these types of array=>charge controller=>battery bank calculations. For example, Midnite has a link for their Classic (and other) MPPT charge controllers:

    https://www.solar-electric.com/mnclassic.html (controller)
    http://www.midnitesolar.com/sizingTool/index.php (tool)

    You fill in the questions (information about solar array, battery bank, local min/max temperatures, etc.) and it will give you the results what will or will not work with their charge controllers.

    And, for a ~210 AH @ 48 volt battery bank, typically the "cost effective" maximum solar array would be ~2,100 Watts... With the panels you asked about ~332 Watt, would be 3 panels in series x 2 parallel strings (if non-freezing climate) and would give you a 1,997 Watt array.

    The basic questions are "what are your loads", what is your expectations (summer weekend, full time off grid, backup genset or not--i.e. oversized solar array, etc.)... For example, if you pulled a 3,000 Watt continuous load from a 210 AH @ 48 volt battery bank:
    • 3,000 Watts * 1/0.85 AC inverter eff * 1/41.0 volt battery cutoff = ~86 amps
    • 210 AH (@ 48 volt battery) / 86 amps = 2.44 hours
    Nominally we suggest that you pull your battery to 50% state of charge (FLA, longer battery life)... Make that 1.22 hours... And pulling high rate of current from a "relatively small" battery bank, the "usable" capacity of the battery bank appears to even be less... Or perhaps ~1 hour.

    This is where I get onto my high horse and talk about a "balanced" system design... If you only need an hour of 3kWatt of power for a day or two, then let the system recharge for a couple days... Then fine.

    Generally, solar is best when supporting relatively small loads (compared to the array+battery bank) for 5+ hours per day (such as evening at home, computer, lights, water pumping, etc.). For example, a typical solar discharge rate would be C/20 (20 hour discharge rate or 5 hours per night, for 2x nights of no solar recharging, to 50% discharge) to a C/8 discharge rate (max continuous suggested current draw from a FLA battery bank. For your proposed bank:
    • 48 volts * 210 AH * 1/20 hour discharge * 0.85 AC inverter eff = 428 Watt AC load, 5 hours a night, 2 days storage, 50% max discharge
    • 48 volts * 210 AH * 1/8 hour discharge * 0.85 AC inverter eff = 1,071 Watt AC load, roughly 4 hours, spread over two days of "no sun"
    Again, none of the above is written in stone--But gives us a decent starting point to understand how system design and the loads play together.

    Could use use Li Ion or AGM batteries and get higher discharge ratings (C/1 for some)--Yes... But at the expense of shorter runtimes (expensive batteries high current output, discharge faster because of less AH capacity vs "cheap" FLA batteries). I.e., A C/1 discharge rate for 210 AH @ 48 volts:
    • 210 AH * 48 volts * 0.85 AC inverter eff * 1/1 discharge rate = 8,568 Watts of AC output (high end Li Ion or AGM or other chemistry)
    • 60 minutes * 70% capacity (90% to 20% state of charge) = 42 minutes of operation
    I cannot say what will, or won't work for you... Your loads and energy needs sort of decide that. Energy usage is a highly personal set of choices--We just want to make sure you get a system that meets your needs (and at a reasonable cost).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • spacebass
    spacebass Registered Users Posts: 87 ✭✭
    edited August 2019 #10
    Dear Bill ,Thank You for your massive answer , I don't understand this line :  

    3x Imp~37 volt Vmp panels in series are getting close to too high of Voc-array-cold (if will be in freezing climate) for a ~150 VDC Max input MPPT charge controller. If in a warm climate (island/tropics/etc.) may work OK.

    I have 4 panels. 

    Are You saying that if I upped the array to 3 panels in series x 2 ( or times 1?)  it would be more ideal for the 150 volt mppt controller as I AM in the tropics and daytime temperature is around 30' all the time.

    Would it make sense to try running 1 string of 3 panels in series on my current 24 voltt system with same controller for now ?

    My requirement is to run my basic devices 24/7 without going to AC. I know this is subject to sun availability in the day.

    I am on grid and can use it to power high power devices at will , any higher power item below could be made to grid if marginal.

    These are 2:x inverter fridge freezers rated 150 watts each , 1 ceiling fan rated 85 watts,  1 led TV 100 watts 4 hours a day ( could be made grid if problem ) , 1 x microwave 1,200 watts 10 minutes a day, 1 water heater 600 watts 30 minutes a day (10 x 3 minutes) , led lights 50 watts 12 hours at night .

    Now with 24 volt 2 x  12v 210 ah batteries and array as above 4 panels, I am going well  into the night before it switches to AC when depending on how much sun the day before,   Now is summer in Thailand so more cloudy than the 'winter' months worst case is now

    Do You feel twice the battery capacity / 48 volts would take me through the night?

    Thanks

    David F 
  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    @spacebass
    That's correct, 2 panels in series, VMP 74 volts is not high enough to reliably charge a FLA battery with a MPPT controller. Three in series will work if in a very warm climate (no cool winters)

    Rick
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Good Day David,

    There is a "dance" you have to play when matching Solar Panels with Battery Bank voltage--And the type (MPPT or PWM) charge controller to get everything to play together "nicely".

    The issues include--Vmp falls as panels get hot (Hmm, solar panels under full sun usually get "hot"). So, you have to account for your Vmp-array to fall as the panels get hot (can fall to near 80% of Vmp-std standard test condition of ~25C). So, you need Vmp-hot high enough to run the charge controller.

    And Voc-cold--When panels get below freezing, Voc (voltage open circuit) can go higher--So you have to make sure Voc-array-cold is less than Vpanel max for the charge controller.

    And for the charge controller, they need to have the Vpanel voltage higher that Vbatt charging voltage... For a PWM type charge controller, you need Vmp-array to be around 72-80 Volts Vmp-array-std.

    And for MPPT controllers, you need even higher voltage to run in "MPPT" mode... More or less, around 1.3x minimum battery charging voltage... If you run Vbatt-charging~60 volts (using nice round numbers), then 1.3x Vbatt = 78 Volts minimum... And again, Vmp falls when panels get hot, so in theory 78 volts / 0.80 hot panel derating ~ 97.5 volts.... That is a bit higher than most folks run, but getting your Vmp-array-std around 80-100 volts is a good idea.

    And your panels with Vmp~37.5---2x panels in series = Vmp-array-std~75 volts ... Which is fine for a PWM controller, but kind of low for a PWM type charge controller.

    So--For a PWM controller, your 2s x 2p array will work OK.

    However, for a MPPT controller, you really need a 3series array and 4series is too high (for a 150 volt controller).... And one of the other configuration "rubs"... With 2s and PWM, you can have 2, 4, 6, etc. panel arrays. With 3x you can have 3, 6, 9, etc. panel arrays (for your Vmp~37.5 volt panels).

    The above is referencing a 48 volt battery bank... If you run a 24 VDC battery bank, then 2series is fine for MPPT, or even 1series is OK for PWM charge controller....

    Sorry if the above is confusing--Because it is. You are juggling 4 sets of balls here (panel ratings, charge controller ratings, battery bank ratings, and even local min/max temperatures) to get everything to play together well.

    Grid is usually cheaper (kWH per $$$) than solar+battery+charger+inverter+maintenance... But if you have (for example) unreliable power (some places have afternoon power outages--Others may have week long outages for no apparent reason)---Then solar (or solar+genset) is just part of the game you play to have reliable power for your needs (i.e., refrigerator/freezers, lighting, laptop computer, cell phone charger for 100% power--Stuff like A/C, only when you have mains/grid power)...

    You have 2x Inverter Refrigerator/Freezers? If so, that can be really nice. Inverter powered compressors for refrigeration do not have the "ugly" starting surge current that standard compressors do (and here in the USA, we don't actually see a lot of inverter powered compressors appliances just yet--Seem to be more popular in other countries at this point).

    But to give you an idea of the difference between power (the rate of energy usage in Watts) and Energy (Watt*Hours or kiWH--The total amount of energy used in 1 day, etc.)... The comparison between a single 150 Watt refrigerator running 24 hours per day and a Microwave at 1,200 Watts for 10 minutes per day.
    • 150 Watt Fridge * 0.50 duty cycle (runs 30 minutes out of every hour) * 24 hours per day = 1,800 WH per day
    • 1,200 Microwave * 10 minutes / 60 minutes per hour = 200 WH per day
    The microwave needs >1,200 Watt inverter to run (high power device vs 150 Watt fridge). But uses 1/9th the amount of energy of your single refrigerator. So, while people think the microwave is a big appliance on solar (and its peak power is), the actual overall energy used by the lowly refrigerator over 24 hours is 9x more.

    Note, many appliances have "gotchas"--Things that are not obvious For example, your nice inverter refrigerator draws 150 Watts starting and running--Very nice. However, that is only true for a refrigerator that you manual defrost.

    For a frost free refrigerator, they typically have a ~600 Watt heating element that runs for ~1-2 hours out of every 12 or 24 hours (to defrost the evaporator of ice that collects during cooling). So, you still may need to have an over 600 Watt inverter for that defrost cycle (I am guessing a bi here--This is based on my experience with US non-inverter refrigerators---It is possible that frost free inverter-refrigerators in your location have different operational methods to defrost).

    And if you want to run your microwave and refrigerator at the same time, then you are looking a 1,200 Watts + 600 Watts (if you catch a defrost cycle for the fridge) or 1,800 Watts just for those two loads.

    Add a second refrigerator, an electric hot water heater, TV (100 Watts seems high for a modern LED TV), lighting, etc. -- All this adds up. And with off grid solar, you do not have a virtually unlimited supply of power/energy from the utility--You are your own utility and you have to make these power usage estimates, and pick your appliances that you want to run from solar. Off grid solar is expensive, and you have to make tradeoffs (i.e., no microwave when grid power is down, backup propane or other fuel fired water heater, etc.).

    And when you ask the question "will 48 volts" power these loads overnight... It is not really a simple answer. Power is Voltage*Current, and Energy is Power*Current*Time (in hours). So, you could have:
    • 48 volts * 400 AH battery bank = 19,200 Watt*Hours of stored energy
    • 24 volts * 800 AH battery bank = 19,200 Watt*Hours of stored energy
    You have to use both battery bank voltage and Amp*Hours (storage) to figure out how much energy you have/will need overnight.

    Generally, for lower power battery systems, we use 12 volts to power ~1,200 to 1,800 Watts of loads. Use 24 volt system for upto 2,400 Watt to 3,600 Watt loads. And over ~2,400 Watts, use 48 volt battery banks... Note these are for peak continuous power.

    Then there is sizing for stored energy... For many reasons, I suggest around an 800 AH battery bank maximum... So, if you calculated you need a 12 volt @ 1,000 AH battery bank, then I would suggest a 24 volt @ 500 AH  or possibly 48 volt @ 250 AH battery bank... All three of these battery banks store the same amount of energy but each bank has its advantages and disadvantages--And may be modified by what size/type of batteries you can purchase locally.

    What is difficult for me--I am doing a lot of hand waving about sizing your system without details about your energy needs... It is a lot like me trying to hand wave the best vehicle for you and talking about motorcycles, compact cars, pickup truck, or 18 wheeler (or whatever you call long haul trucks)... Each has its place, but if you only hall 120 tons once a year, and the rest of the time it is 50 KG of groceries once a week--Then a "road train" truck&trailers are probably not a cost effective answer for your needs.

    For off grid solar power... A small system is something like 500 to 1,000 WH per day (lights, small water pump, laptop computer). As soon as you add a refrigerator and TV, you are looking at near 3,300 WH per day (I would call this a "medium size" system)... Add a 2nd fridge, well pump, clothes washer, electric water heater, some A/C... You are looking at 10,000 WH per day (a large system).

    To design and build a cost effective off grid power system that meets your needs--You really need to get a handle on your power/energy usage... In the US, off grid solar power is around 5-10x more expensive than Grid/Utility power (when you add up everything include ongoing new batteries every 5-8 years, new hardware every 10+ years, backup genset+fuel, etc.).

    If you do not have one, you should get a 220 VAC (or whatever your line voltage is) Watt*Hour meter and measure the power/energy usage of each appliance/device you want to run from solar (using Amazon UK as an example of 220 VAC WH meters, not sure what you need in Thailand):

    https://www.amazon.co.uk/s?k=kill+a+watt+meter

    Sorry to be so confusing... You are still "starting in the middle" and the answers are "less constrained". Better understanding of your loads/energy needs/and are you looking for full time off grid or just occasional power outages or what... Will make it easier to give you better answers (and tell "the story" from the beginning rather than plot points randomly).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    With the panels being almost 70Voc the choice of controller is somewhat limited, Midnight have 200 and 250 volt versions, Schneider and Morningstar 600V, the latter would allow all 6 panels to be configured series. The controller cost versus alternative panel costs would have to be considered as well as availability of existing panels should extras be needed if they are to be utilized. 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.