Help Designing Schematic

Several years ago I posted here about setting up a solar system. We are finally to the point of setting this all up and I could really use help with a proper schematic. We are using a Tesla car battery and have 1020w (4x255w) panels. Our goal is to have a plug for shore power, a generator, and a 3000-4000w Aims inverter with auto generator on capability. We are going to also need a 24v to 12v step down so we can run a few things such as fans, lights, and a water pump.

Previously we purchased a Renogy charge controller but never opened it once we found out that it can only handle 500w (or maybe it was 800) of panels. We were looking at the Midnight Classic but anything that works properly will do.

Lastly, if there is a way to hook into the RVs current 12v system via inverter to charge while driving. Our solar panels will be put away while moving and still being able to charge would be wonderful.

I hope this is enough information for everyone and I appreciate any help. If you're interested in viewing the project please check out our site at http://Sasquatters.com

Comments

  • mcgivormcgivor Solar Expert Posts: 3,126 ✭✭✭✭✭
    edited October 2 #2
    You might want to start by reading this link https://www.mobile-solarpower.com to get some information. 
    Regarding charging with an alternator, lithium batteries have such low impedance they overload the alternator, there are some videos on YouTube by Victron Energy worth watching if this is something that is planned.
    Controller wise Midnight is cooled with fans which are reported to be loud, a passively cooled may be a better choice if used inside the bus, examples that can be programmed for lithium are Victron, Morningstarand Schneider. Also consider PWM if there is any shading, as series wired for MPPT will be compromised by any shading, even partial.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • sasquatterssasquatters Registered Users Posts: 41 ✭✭
    edited October 3 #3
    Thanks for your message. I have read and read and that is why I am asking here. There is SO much information, let alone conflicting information, that I would really like a consensus. The link you posted seems to have a layout here but it seems too simple?
    The alternator would go through a charge controller wouldn't it? I'm not sure how that would affect the battery.
    I've also heard about the fans on the midnight. The Renogy one we have has a large heatsink and no fan, but like I said, unfortunately we can't use that one anymore.
    I've heard that two MPPT controllers may be the way to go for shading issues. We have one set of two on each side of the RV and shading is a possibility. One MPPT per side may be good, yes?
  • EstragonEstragon Registered Users Posts: 4,118 ✭✭✭✭✭
    With different orientation panels/arrays, separate controllers would almost certainly be better.

    Realistically, 1kw STC rated panels likely won't produce much more than ~750w.  With 2 controllers say 375w ÷ 22v = 17a.  There are lots of fanless controllers in that size range.

    In theory, you could use a 12vdc to 120vac inverter to power a 120vac to Xvdc rectifier (battery charger) to charge while driving.  Not pretty, but it could limit the load on the alternator if the charger was sized/set properly.
    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
  • mike95490mike95490 Solar Expert Posts: 8,434 ✭✭✭✭✭
    Any Lithium based battery will need it's own BMS (battery management system) to prevent catastrophic over & under charge.
    As long as your charging source meets the BMS standards, it can be raw PV connections, 24V alternator, mains powered Charger, Solar Charge controller output...... (the list can go on and on....)

    The BMS and it's interaction with the charging source is the critical thing to watch.  Learn what the valid inputs are, learn what your charge device is capable of.
    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 ,

  • sasquatterssasquatters Registered Users Posts: 41 ✭✭
    Okay, so with the information I provided what do you suggest?
  • BB.BB. Super Moderators, Administrators Posts: 29,644 admin
    We try to design "balanced" systems... Your loads -> Battery bank. And the Battery bank defines the solar array (5% to 20% rate of charge), and the location/mounting hours of sun vs loads to define solar array size too (flat to roof, tilt, where you will be dry camping, north/south and seasons (south summer lots of sun, north winter, not much).

    Your 3,000 Watt AC inverter is on the large side for a portable system--And if you really want to run it, you would need something like 600 AH @ 24 volt lead acid battery bank to power it at rated power:
    • 3,000 Watts * 1/0.85 AC inverter eff * 1/21.0 volts minimum battery bus voltage = 168 Amps current worst case
    If flooded cell lead acid, in "golf cart" battery terms, that would be 4x 6 volt @ 200 AH FLA GC batteries in series (for 24 volt battery bus), times 3 parallel strings (for 600 Amp*Hour bank) for 12 GC batteries total.

    I believe you are doing school bus conversions... So you may have more room/weight capacity than the average RV, but that still a goodly amount of battery bank.

    If you just put two 12 volt x 100 AH batteries in series for a 24 volt @ 100 AH battery bank, a full load on your  3kW inverter (at 3kWatt load) would take that small bank "flat/dead" in 30 minutes (probably less).

    For a "cabin" or smaller, very efficient off grid home, I would be suggesting a 1,200-1,500-1,800 Watt AC inverter to run an energy star 120 VAC refrigerator, LED lighting (probably AC), RV water pump, laptop+cell phone charger, and a small clothes washer.

    More or less, as a starting point, your Solar array Wattage will (very roughly) equal you AC inverter capacity (i.e, a 3,000 Watt AC inverter and upwards of a 3,000 Watt Solar array).

    Lithium Ion (LiFePO4 typically) are very nice batteries. High surge current and no maintenance. Downside is that they usually need a BMS (battery management system) to prevent damage to the Li Ion battery bank (avoid over and under voltages, some limit maximum current draw). Also, Li Ion batteries typically cannot be recharged under ~25-32F (need to keep above freezing when being cycled).

    Other issues with large AC inverters is that they may take upwards of 30-40 Watts just being "turned on". Smaller AC inverters can be 6-12 Watt range. A 3 kWatt inverter taking 40 Watts (40 Watts * 24 Hours = 960 Watt*Hours)--That is almost the same amount of energy that a full size refrigerator/freezer needs (~1,000-1,500 WH for fridge).

    Understanding your loads and limitations of the installation (and how much you want to spend), location, etc., help to define the system design. I would suggest you will make multiple paper designs until you come up with your "optimum" design for your needs.

    I (we) try to avoid telling you about the systems we would design--The system needs to meet your needs, not my needs, or my guesses about your energy needs.

    What is the Tesla battery bank voltage and AH (Watt*Hours/kWH) size?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • EstragonEstragon Registered Users Posts: 4,118 ✭✭✭✭✭
    Also, do you plan to use the Tesla car battery intact (including charger & bms)?
    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
  • sasquatterssasquatters Registered Users Posts: 41 ✭✭
    edited October 7 #9
    BB. said:

    What is the Tesla battery bank voltage and AH (Watt*Hours/kWH) size?

    -Bill
    Thanks for the info. Seems to be a lot about lead acid which we have no interest in using so I am not sure how that information relates. As far the question I quoted, I used a calculator I found online. The battery is about 4.3kwh so at 24v it looks like its about 175 amp hours. does that seem right?

    Estragon said:
    Also, do you plan to use the Tesla car battery intact (including charger & bms)?
    No. It came from a company that hooks their own board to it and allows an aftermarket BMS.


  • mcgivormcgivor Solar Expert Posts: 3,126 ✭✭✭✭✭
    The use of an inverter charger would have several advantages being it would allow direct generator or shore power charging while supporting loads similtaniously. Often the sum of the individual components equal or exceed the cost of the inverter charger, additionally the quality of most are superior to lower rung offerings such as Aims.

    Having components that are able to communicate with one another is another advantage both AC charger and charge controller can be programmed with the same charging profile which is very important with lithium batteries. Most charge controllers along with AC chargers are specifically designed for lead acid batteries which don't correspond to lithium batteries.

    My suggestion is to get components that are known to work and source a BMS compatible with the cells. This will make the entire 
    project simple in contrast to using mismatched incompatible components. Personally I use Schneider equipment with LFP batteries, so my experience is strictly with that brand, Outback has equipment that is similar and known to work.


     
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • Marc KurthMarc Kurth Solar Expert Posts: 550 ✭✭✭✭
    edited October 8 #11
    Please be aware that 4.3 KWH is a fairly small battery bank for a large RV, even considering the usable depth of discharge for Lithium. Large bus size motor homes generally have larger battery banks - and often much larger, for rigs intended for living away from shore power.
    I do not mean to infer that it cannot be done, only that you need to be fully aware of what it takes to achieve your goals. Of course, everything hinges on your loads, but understand the ramifications of having a 3KW to 4KW inverter on a 4 KWH battery bank.
    I always have more questions than answers. That's the nature of life.
  • mcgivormcgivor Solar Expert Posts: 3,126 ✭✭✭✭✭
    Please be aware that 4.3 KWH is a fairly small battery bank for a large RV, even considering the usable depth of discharge for Lithium. Large bus size motor homes generally have larger battery banks - and often much larger, for rigs intended for living away from shore power.
    I do not mean to infer that it cannot be done, only that you need to be fully aware of what it takes to achieve your goals. Of course, everything hinges on your loads, but understand the ramifications of having a 3KW to 4KW inverter on a 4 KWH battery bank.
    I would agree in principle that a 4.3Kw battery is rather small in relationship to the proposed inverter of 3Kw, but as loads are unknown it's rather early to suggest what the battery capacity should be.

    The common mistake is to select an inverter with a capacity greater than what is required, and o,r greater than battery capacity. In the past  I've tried to explain the process of loads first, then battery and finally PV to support to the OP, however it seems to have fallen, for the most part,  on deaf ears.

    The one advantage with lithium batteries is it is easy to add capacity without the penalty associated with LA, it is however better to do it right in the first place is the better approach.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • Marc KurthMarc Kurth Solar Expert Posts: 550 ✭✭✭✭
    mcgivor, Yes, of course. When customers ask my help in sizing a battery bank, I require them to send me a spreadsheet of their loads and operating time for each. I won't waste my time using guesses. Note that I said: "Of course, everything hinges on your loads.........."
    My point was to provide a frame of reference for what I typically see in bus sized RV and bus conversions.
    Marc

    I always have more questions than answers. That's the nature of life.
  • BB.BB. Super Moderators, Administrators Posts: 29,644 admin
    Lead Acid batteries are not a bad place to start... And simply using the same numbers for a Li Ion pack will get you started.
    77
    Li Ion tend to be known for high surge current support--But many of the Li Ion batteries do have hard limits on surge current that limits them to Lead Acid or less of similar AH. Need to know the details when designing your system.

    And another reason why FLA rules of thumbs work for other batteries (AGMs are >90 efficient, even upwards of 98% or so--Similar to Li Ion).

    The big differences include that Li Ion do not have to be recharged to near 100% capacity within a day or so (especially if to sit unused). And Li Ion typically last longer if stored at 50% SoC (or at least, do not exceed 90-95% SoC for longer life).

    And it really does go back to your loads and energy needs... Typically we size a Lead Acid bank to use nominally 50% to 100% State of Charge (with occasional discharge down to 20% SoC). And a Li Ion battery around 20%-90% state of charge--Which gives you a useful capacity of around 70% of battery capacity--Whereas lead acid we suggest a typical cycle of 25% to 50% of battery capacity...

    The issues become--If you use your Li Ion battery to cycle 70% every day--They are certainly capable of doing that. With Solar, a Lead Acid battery should be cycled something like 25% per day (it is difficult to fill a Lead Acid battery from 50% or less SoC to 100% in one solar day--Simply not enough hours of sun in the sky to fully recharge a Lead Acid bank deeply cycled in one day.

    So we have the 2 days of "dark" plus 50% max discharge or ~25% depth of discharge for 2 days of dark. This helps to avoid generator use if the next day or 2 is stormy weather.

    If you size your system to use 70% of Li Ion capacity (small/light weight battery bank, and save some $$$ too where as Lead Acid tends to be big, heavy, and cheap per AH/kWH of storage)--You are left with "going dark" waiting for the next day of sun, or using a genset.

    The sizing of 5%-10%-20% rate of charge is a good rule of thumb for sizing a Li Ion system too... While the technical reason is that FLA and other lead acid batteries typically have minimum rates of charge and equalization power requirements that simply are not required for Li Ion type banks.

    However, the 5% and 10% minimum are also good numbers to get a battery bank recharged quickly... You don't want to take 2+ days to recharge after one "dark day" of energy usage (i.e., 5% rate of charge * 5 hours of good sun = 25% charge cycling--Good minimim for summer solar). More panels, "less day to day power management when off grid".

    And this comes back to balancing loads against Battery Bank Capacity. Flooded Cell Lead Acid battery banks tend to be "oversized" to handle large loads (like starting a well pump)--But when you match with 2 days of dark, and 50% max discharge--The typical FLA Bank will generally have enough surge current to support the typical "matching" AC inverter capacity and surge loads.

    Li Ion generally support surge loads better--Allowing you to reduce bank AH/WH capacity vs FLA... However, you still have the "raw capacity" question... How many AH (at XX Volts) or Watt*Hours per day, and how many "dark days" do you want your system to support before starting the genset. If you size a Li Ion bank to do 70% cycling or even 35% cycling per day, after you "hit" the 20% bottom (or whatever you choose to use), you have effectively "zero" battery energy left... Where as our 2 day/50% limit, still gives you another 30% capacity between 50% and 20% for occasional use during bad weather/etc. So our FLA rules of thumb give the owner a bit more room for energy management/genset use.

    For Li Ion battery banks with "minimum AH/WH" capacity... You have to know and manage your loads with more care. Or else you end up with more genset time/or more "darkness" than you would have liked. If only Li Ion Batteries were not so expensive--Then could throw some more reserve capacity at the issue and be a bit more loose with system planning.

    And only you know your loads... Typically for off grid use, I suggest maximum conservation and the most efficient appliances/inverters/etc. you can find. The typical cabin/RV may have many hours of small loads (5 hours of lights, charging laptop and cell phones, a small fan for summer use, and a small RV Water pump for tens of minutes per day).

    If your bus was also your job vehicle--Perhaps running a skill saw, air compressor, etc. or relatively short bursts of high power/current--Not hours of high power...

    Just to give you an example, a Microwave is a tough load--But for other reasons a typical desktop computer can be worse:
    • 1,500 Watts microwave * 1/3rd hour per day usage (20 minutes per day) = 500 Watt*Hours
    • 300 Watt desktop computer * 8 hours per day = 2,400 WH per day
    • 30 Watt laptop * 10 hours per day = 300 WH per day
    • 12 volt * 8 amp RV water * 1/2 Hour per day (30 minutes) = 48 WH per day
    • 8 Watt LED * 5 lights * 5 hours per night = 200 WH per night
    • 40 Watt AC inverter Tare Load (larger AC inverter have larger Tare) * 24 hours per day = 960 WH per day (if running 24x7)
    • 120 Watt refrigerator * 1/5 hour duty cycle * 24 hours per day = 1,440 WH per day
    As you can see, small loads * lots of hours of use per day = lots of WH/AH of battery bank usage.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • sasquatterssasquatters Registered Users Posts: 41 ✭✭
    edited October 8 #15
    BB. said:
    Just to give you an example, a Microwave is a tough load--But for other reasons a typical desktop computer can be worse:
    • 1,500 Watts microwave * 1/3rd hour per day usage (20 minutes per day) = 500 Watt*Hours
    • 300 Watt desktop computer * 8 hours per day = 2,400 WH per day
    • 30 Watt laptop * 10 hours per day = 300 WH per day
    • 12 volt * 8 amp RV water * 1/2 Hour per day (30 minutes) = 48 WH per day
    • 8 Watt LED * 5 lights * 5 hours per night = 200 WH per night
    • 40 Watt AC inverter Tare Load (larger AC inverter have larger Tare) * 24 hours per day = 960 WH per day (if running 24x7)
    • 120 Watt refrigerator * 1/5 hour duty cycle * 24 hours per day = 1,440 WH per day
    As you can see, small loads * lots of hours of use per day = lots of WH/AH of battery bank usage.

    -Bill
    Since calculating all of this we got a split unit AC which several people have and seem to have no problem running with the battery we got. What do you think? I thought that Aims hardware was good but from what I am gathering here it doesn't seem to be favored. I was also looking at the Victron stuff but they don't seem to have an auto generator on or shore power (which we will likely never be connected to) functions.





  • mcgivormcgivor Solar Expert Posts: 3,126 ✭✭✭✭✭
    edited October 9 #16
    @sasquatters

    Fridge. - 454kwh/yearly (24 hrs)
    8x Light bulbs - 9w (5 hrs not all on at once)
    Modem - 11.40w (24 hrs)
    TV - 54w 135w max (5 hrs)
    LP Water Heater - 10w (24 hrs)
    Computer - 12w - 18w on load - 60w when charging
    x8 Light switch - 0.59w
    x16 Outlet - 0.75w
    Above is a cut and paste from previous post.

    Below a rough estimate on load demand 

    Refrigerator will use ~1500 wh
    4 lights for 5 hours 36 wh
    Modem 300 wh 
    TV 350 wh using 50% of maximum power 
    LP Water Heater 240 wh 
    Computer 240 wh estimate
    Light switches  113 wh
    Outlets 288 wh
    Aims inverter model PICOGLF30W24V120VR  1160 wh 

    The total for these is 4227wh not taking into account inefficiencies of the inverter, your Tesla 4KW module using 70% of capacity (recommended ) is 2800 wh,  so a second battery module, or better yet a third would be required.

    The PV needed to support this capacity is in excess of the 4 × 255w panels you currently have, even at the equator where horizontal mounting is optimal.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • Marc KurthMarc Kurth Solar Expert Posts: 550 ✭✭✭✭
    sasquatters
    "Since calculating all of this we got a split unit AC which several people have and seem to have no problem running with the battery we got. What do you think?"
    What is your total KWH day consumption? 
    How often do you expect to run the generator, and how long?

    I always have more questions than answers. That's the nature of life.
  • EstragonEstragon Registered Users Posts: 4,118 ✭✭✭✭✭
    Personally, I wouldn't see auto generator start as a deal breaker in choice of inverter for a couple of reasons:
    - There are a lot of things that can go wrong starting and running a generator.  Doing it manually when you have a fighting chance to correct the problem before it gets out of hand has a lot to be said for it.
    - Duplicating the behavior of auto-start based on battery voltage or whatever shouldn't be all that hard of a problem.  Lots of decent inverter/chargers have aux ports that can be set up to trigger a relay.

    I have no experience with Aims inverters, but the fact they make really large wattage 12v inverters makes me question their judgment.

    A load like a split AC system can work well on solar, if there's enough peak solar to both  run the load and charge the battery, and/or you can run the load once the battery is nearly full.
      
    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
  • sasquatterssasquatters Registered Users Posts: 41 ✭✭
    The PV needed to support this capacity is in excess of the 4 × 255w panels you currently have, even at the equator where horizontal mounting is optimal.
    Wouldn't it just be a slower charge? Those usages you pasted are not every day things. I was considering a second module however. How does the Tesla compare to the Nissan Leaf modules?
  • mcgivormcgivor Solar Expert Posts: 3,126 ✭✭✭✭✭
    The PV needed to support this capacity is in excess of the 4 × 255w panels you currently have, even at the equator where horizontal mounting is optimal.
    Wouldn't it just be a slower charge? Those usages you pasted are not every day things. I was considering a second module however. How does the Tesla compare to the Nissan Leaf modules?
    Yes a slower charge would compensate if the sun were available for 12 hours, unfortunately the peak production is limited to an hour or so with increase before and decrease after, the time is dependent largely on latitude as well as season.

    Question, do you actually have the Tesla batteries or are you considering? If considering you may want to use a safer chemistry such as Lifepo4. 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • sasquatterssasquatters Registered Users Posts: 41 ✭✭
    edited October 16 #21
    We already purchased it. I was looking at Lifepo4 but they didn't seem to have much capacity. I contacted the Tesla company and they said I could return it. I'm just confused because I've seen several people in RVs using them and being able to run all their stuff as well as their AC.

    The AC we have (and are not returning) is the Mr. Cool DIY 115. I would like to be able to run this off our solar. I am also ditching the fridge and getting a 12v one.

    Here is our new usages (without the AC)
    Fridge. - 56w/ 24 hrs
    5x Light bulbs - 9w/ 5 hrs
    Modem - 11.40w/ 24 hrs
    TV - 135w/ 5 hrs
    LP Water Heater - 10w/ 24 hrs
    x8 Light switch - 0.59w

  • mcgivormcgivor Solar Expert Posts: 3,126 ✭✭✭✭✭

    We already purchased it. I was looking at Lifepo4 but they didn't seem to have much capacity. I contacted the Tesla company and they said I could return it. I'm just confused because I've seen several people in RVs using them and being able to run all their stuff as well as their AC.

    The AC we have (and are not returning) is the Mr. Cool DIY 115. I would like to be able to run this off our solar. I am also ditching the fridge and getting a 12v one.

    Here is our new usages (without the AC)
    Fridge. - 56w/ 24 hrs
    5x Light bulbs - 9w/ 5 hrs
    Modem - 11.40w/ 24 hrs
    TV - 135w/ 5 hrs
    LP Water Heater - 10w/ 24 hrs
    x8 Light switch - 0.59w


    The Tesla batteries have a slightly higher energy density than Lifepo4 which makes them attractive for mobile applications, the downside is they use cells which are considerably more dangerous, making a BMS all the more important. Not sure what's meant by lifepo4 being of low capacity, it is possible to build whatever capacity is needed with individual cells or by series  parrallel connected drop in replacement type

    As pointed out previously your load demands exceeds that of a single single Tesla module, that's not including the use of A/C, which itself would likely need a single module, depending on useage, or if used during the day would need a significantly larger array to power it and replenish the battery. From what I'm seeing unless extensive use of a generator along with a much higher capacity battery  is not part of the equation it unlikely, or more realistically impossible,  that the proposed system will be capable of supporting the proposed loads. 

    This may sound negative but it's not by any means, being off grid requires careful calculation, conservation along with an understanding of the limitations of the equipment. All too often people make the fundemental mistake of overestimating the capabilities of their system, which lead to dissapointment. Once a firm load calculation is established then the battery is sized accordingly then the array, and or the amount of generator support acceptable, if there are shortcomings in the charging ability then the unnecessary fat needs to be trimmed. 

    Many here have made mistakes in the past, including myself, the object of passing on suggestions is to minimize the potential of you doing just that, be aware that  there are many videos on YouTube and the Internet in general that are often very misleading.


    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • sasquatterssasquatters Registered Users Posts: 41 ✭✭
    edited October 18 #23
    What do you think about 6 Battle Born LiFePO4 batteries? Would that do it? I realize it may charge slower, but that is fine considering the AC would not be a daily occurrence.

    I am about to purchase this fridge. It is MUCH better than the one I posted previously, yes? I want to make sure this will work better over our current 120 one.
  • EstragonEstragon Registered Users Posts: 4,118 ✭✭✭✭✭
    For me, the link didn't go to a particular fridge.
    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
  • sasquatterssasquatters Registered Users Posts: 41 ✭✭
    UGP-290L1
    Unique 10.3 cu/ft Solar Powered DC Fridge

  • EstragonEstragon Registered Users Posts: 4,118 ✭✭✭✭✭
    Thanks.  It appears to be a danfoss based 12/24v compressor.  I have several.  Running 12v avoids inverter losses (call it 20%), and the danfoss compressors are pretty easy starting vs trying to start a typical US AC fridge.  Downsides are they aren't great at getting (vs keeping) a lot of stuff cold, and will need periodic defrosting.  My danfoss stuff is all site-built or converted ice boxes.

    FWIW, I use a Unique range, and it's good at what it does.
    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
  • mcgivormcgivor Solar Expert Posts: 3,126 ✭✭✭✭✭
    What do you think about 6 Battle Born LiFePO4 batteries? Would that do it? I realize it may charge slower, but that is fine considering the AC would not be a daily occurrence.

    I am about to purchase this fridge. It is MUCH better than the one I posted previously, yes? I want to make sure this will work better over our current 120 one.


    Battle Born are a simple solution for those who don't want to deal with building a DIY pack, the support, based on my inquiries, appears to be very good, they answer all questions in detail. They would be, in my opinion, a good choice for someone looking for a safe solution with support from the manufacturer.

    The capacity needed is dependent on loads, 6 × 100 Ah may be close if some conservation is applied, the DC refrigerator is a positive move, an inverter which can be programmed to shut down overnight when not needed would help dramatically, all those small parasitic loads, including the inverter self consumption really add up.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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