300 watt solar panels and 600ah battery bank only lasting one day?

chriselkschriselks Posts: 13Registered Users ✭✭
Looking for tips on improving my overall system right now I have 3/100watt panels wired in parallel into a tracer 30amp mppt controller and feeding 6 101 ah deep cycle batteries only running low watt led lights mostly and it only lasts about 2 days total

Comments

  • PhotowhitPhotowhit Posts: 4,747Solar Expert ✭✭✭✭
    6 - 12 volt?

    You are quite a bit under paneled, most manufactures want at least a 10% charge rate, you have about 225/14= 16 amps available to charge a 600 amp bank or about 16/600= 2.6% charge rate.


    Watt is the total wattage of the lights? are they AC lights? are you running an inverter as well?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • chriselkschriselks Posts: 13Registered Users ✭✭
    edited June 13 #3
    They are AC lights 9 Watts a piece and there are 5 I’m running a 1200 watt modified sine inverter it’s all 12v. How many panels do you recommend to get me where I need to be? I’m new to all this so bear with me
  • chriselkschriselks Posts: 13Registered Users ✭✭
    I have a 24 volt inverter on the way so the whole system will be 24 v soon
  • EstragonEstragon Posts: 2,962Registered Users ✭✭✭✭✭
    One issue may be the voltage of the panels in parallel (especially if they're warm/hot) may be too low for an mppt controller to use for charging. Series wiring may help if the 100w panels are a typical nominal 12v (~18vmp). You would need to check the open circuit voltage maximum voltage the controller will take to see if the three panels could be wired in series. If you end up going to 24v, the parallel wiring won't work.

    Getting a system that works well for you always starts with loads. What is the system going to run, and how many hours/day?

    A good sized 24v inverter could use about as much just being on as your lights use. If you run the lights 12hrs/day, the load is 9 x 5 =45w x 12hrs = 540w. Battery power required for losses plus load could double that.

    The lights themselves may be DC, using a small transformer (wall wart) to go from 120vac to (likely) 12vdc. Running the light directly off DC might make more sense if the lights and batteries are fairly close together.

    Anyway, it would help to know more about intended loads before going further.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • chriselkschriselks Posts: 13Registered Users ✭✭
    As of now I’m getting 17volts and 8-9 amps with all 3 panels wired in parallel. It’s running a completely off grid tiny home. We run light for a few hours during the day and a fan at night every day and about 1-2 hours of tv(led 32 inch pulls 30 Watts at 120v) would like to be able to upscale to run a small refrigerator if possible
  • mike95490mike95490 Posts: 7,970Solar Expert ✭✭✭✭
    adding a small fridge will nearly require going to 24V with all the other loads you have.  And a bunch more panels,
    you will eventually have a 24V 300ah bank, which needs 30A to properly charge.  That would require about 1,000w of panels.

    Currently, the system you put together is not well engineered, and that's why the batteries go dead.  Since that's happening, your current batch of batteries is likely toast.   Get them charged up from your generator, and maybe by using $20 of fuel, you can save $600 of batteries.
    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 ,

  • chriselkschriselks Posts: 13Registered Users ✭✭
    My next question is how much panel will my 30 amp mppt tracer 3210 be able to handle at 24v would I be able to run 4 270 watt 24v panels?
  • littleharbor2littleharbor2 Posts: 1,072Solar Expert ✭✭✭✭
    This should help

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • PhotowhitPhotowhit Posts: 4,747Solar Expert ✭✭✭✭
    A little help reading the chart, the max rate of charge would be 780 watts at 24 volts. Since panels can only produce about 75% of their rated wattage you can be expect to get pretty much maximum value (cost effective) from an array up to 1040 watts (75% of 1040 = 780) so you would be about at the max for the charge controller at 1080 with little waste on a 30 amp charge controller at 24 volts.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • chriselkschriselks Posts: 13Registered Users ✭✭
    So that would be the most effective for me. I’m going to be ordering 4/270 watt panels from renogy today and I will repurpose my 100 watt panels elsewhere. Thank you all so much any other helpful info would be appreciated
  • chriselkschriselks Posts: 13Registered Users ✭✭
    My next question is the requirements to run the small refrigerator I have. I’ve hooked it to my plug in meter and it reads 77 Watts is all it uses and I’m assuming that it runs about 20 minutes of every hour. Would I be able to run that without trouble on the upgraded system?
  • PhotowhitPhotowhit Posts: 4,747Solar Expert ✭✭✭✭
    chriselks said:
    My next question is the requirements to run the small refrigerator I have. I’ve hooked it to my plug in meter and it reads 77 Watts is all it uses and I’m assuming that it runs about 20 minutes of every hour. Would I be able to run that without trouble on the upgraded system?
    It doesn't sound like it would be a problem, making the assumption that you have direct sun light for 3+ hours a day and have your panels angled with in 10 degrees of your latitude angled south in the northern hemisphere...
    ...and no long term damage to your battery bank.


    always hate answering in the affirmative only to find out they solar panels are mounted flat on a camp parked in the shade...lol.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • chriselkschriselks Posts: 13Registered Users ✭✭
    I have the panels mounted at 45 degrees facing south I’m in north Mississippi. I’m charging and swapping 3 batteries at a time keeping them from damaging anything til my new panels arive
  • 706jim706jim Posts: 216Solar Expert ✭✭✭
    Because it may help here I'll post some numbers recently observed at my place. My fridge is rated at 140 watts and cycles probably 40% of the time. To run the fridge overnight, my panels put in 49 A-hr at 24 volts nominal to run the fridge 24 hours or approximately 1.2 Kw-hr for a 24 hour day. This is for an 11.5 cubic foot fridge/freezer similar in size to what would be used in a small apartment.
    Hope this helps with your calculations.
    Island cottage solar system with 1400 watts of panels, Trace DR1524 MSW inverter, Trace C40 PWM controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 26th year.
  • mike95490mike95490 Posts: 7,970Solar Expert ✭✭✭✭
    Is your fridge AC power , or DC ?  Compressor or heater element ?   AC compressor fridges need a larger inverter to be able to start the motor,  the Danfoss DC compressor has an internal motor driver, so you don't need an outboard inverter,
    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 ,

  • chriselkschriselks Posts: 13Registered Users ✭✭
    edited June 19 #17
    Ac with small compressor
  • chriselkschriselks Posts: 13Registered Users ✭✭
    These are the specs on the exact model
  • BB.BB. Posts: 28,088Super Moderators, Administrators admin
    Ideally, it would be best to measure the Watt*Hours (or kWH) per day with a Kill-a-Watt type meter:

    https://www.solar-electric.com/kiacpomome.html

    But, using your numbers, we can estimate your needs:
    • 77 Watts * 20 minutes * 1/60 minutes per hour * 24 hours per day = 616 WH per day (a bit on the "low side" for typical small fridge)
    Warmer days, freezing ice, opening door multiple times per day, putting warm food in to cool, etc. all push the numbers up. For the following, assume 850 WH per day:
    • 850 WH per day * 1/0.85 inverter eff * 2 days storage * 1/0.50 max discharge (for longer battery life) * 1/12 volt battery bank = 333  Amp*Hour @ 12 volt "nominal" battery bank
    Note that this is for a refrigerator only load--If you have other loads, then you need to account for them too. Lets say you want 1,850 WH per day, then the battery size would be around:
    • 1,850 WH per day * 1/0.85 inverter eff * 2 days storage * 1/0.50 max discharge (for longer battery life) * 1/12 volt battery bank = 725  Amp*Hour @ 12 volt "nominal" battery bank
    Note, for various reasons, I would suggest that no more than ~800 AH battery bank. And that you are close to a good fit for a 24 volt battery bank.

    Sizing the solar array... Two calculations. One based on 5% to 13% rate of charge for the battery bank (5% works for weekend/summer cabins. 10%+ works better for full time off grid power system).
    • 725 AH * 14.5 volts charging * 1/0.77 panel and charge controller deratings * 0.05 rate of charge = 683 Watt minimum array
    • 725 AH * 14.5 volts charging * 1/0.77 panel and charge controller deratings * 0.10 rate of charge = 1,365 Watt array nominal
    • 725 AH * 14.5 volts charging * 1/0.77 panel and charge controller deratings * 0.13 rate of charge = 1,774 Watt array "cost effective" maximum
    And then there is sizing the array for the daily amount of power you want to use and the amount of sun you will get. Assuming a fixed array:

    Tupelo
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 41° angle from vertical:
    (Optimal winter settings)

    JanFebMarAprMayJun
    3.53
     
    3.76
     
    4.48
     
    4.87
     
    4.62
     
    4.54
     
    JulAugSepOctNovDec
    4.67
     
    4.72
     
    4.98
     
    4.91
     
    3.92
     
    3.40
     

    Assuming you don't use the system much in winter (or use a genset to help), toss the bottom three months. November at 3.92 hours of sun per day for "break even" solar usage (may need to use genset some if bad weather):
    • 1,859 WG per day * 1/0.52 AC off grid system eff * 1/3.92 hours of sun per day = 908 Watt array minimum
    850 WH per day for refrigerator plus another 1,000 WH for the rest of your loads should be a pretty useful system. If your other loads are not much, you could get down to ~500 WH per day for those other loads and run the calculations again.

    Lots of guesswork here--But should give you an idea of what it would take to run your loads and the math if you want to run the numbers again with your assumptions.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • NANOcontrolNANOcontrol Posts: 82Registered Users ✭✭
    How reliable do you want the fridge to be? Just cooling off some drinks or do you want to leave for a week and be sure the food is still good?  I run a chest freezer as a fridge and it averages about 500W a day. The 7CF freezer is 94W running, 110W to the inverter. If you do this, add another 250W. Of course to work in all kinds of weather it takes about 2KE of panels.  Of course, mine is a unique case with only a single car battery to run the entire house. That extra panel power isn't wasted as it provides all the hot water. Wife even has a dishwasher.
  • petertearaipetertearai Posts: 356Solar Expert ✭✭✭
    My Wife has a dishwasher ......... its called Me !
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . victron battery monitor . 24 volts 450 ah surette batterys . off grid  holiday home 
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