Are my parts working together well

MEK1954MEK1954 Registered Users Posts: 23 ✭✭
This is a new system and all components are new.  I have 4 Monocrystalline 195 watt panels connected in series parallel for 24/38 volts going into a Renogy MPPT 60 amp controller on a good day It will put 38 to 45 amps back into the 4 200 amp hr mighty max battery's connected in parallel putting 12 volts into a Giandel 4000/8000 watt inverter.   I get about 4 to 4.5 hrs of good high charge sun a day (during November). Are my parts working together or is there a mismatch somewhere. And I know there will always be cloudy and rainy days and I would like your advice on a good battery charger to build my battery's back up from days of use.
Thank you for any help you can offer.
Mark



Comments

  • VicVic Solar Expert Posts: 3,082 ✭✭✭✭
    Hi,  MEK..,  Welcome to the Fourm.

    Quick comments:

    Four parallel batteries often cause imbalance in charge and discharge.   You need large interconnecting cables,  and proper attention to having identical-length cables,  wired for the best balance.

    AND,   an inverter with a  GIGANTIC  (and probable overly  optimistic) output power rating,  AT 12 VDC,  will generally WASTE tons of  power,  just sitting idle. 

    On balance,  from the little that i known about your system,   not very well balanced,  IMO. 

    FWIW,  Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • MEK1954MEK1954 Registered Users Posts: 23 ✭✭
    All the battery's join at one point with 4ga wire and 1/0 ga from the batt to the inverter, with no power being used the inverter draws 1.8 amps.
    If you think my components are not very well balanced, what are your concerns?
    Mark

  • VicVic Solar Expert Posts: 3,082 ✭✭✭✭
    Hi Mark,

    First,  the following Link shows some variations on wiring parallel batteries:
    SmartGauge Electronics - SmartBank wiring diagrams

    1.8 A Tare consumption (with no loads),   is not bad.

    But,   really,  one would want to know the purpose/use of your system,   the maximum and minimum loads and the time of day, when they occur,   the estimated average total power consumed from the batteries,  and many other details of your system.

    At 4000 Watts of load on the inverter (if the inverter and batteries could really deliver that),   there is nominally about 400 Amps going into the inverter.   This is a lot of current.   BUT,  probably,  you will not ever place that much load on the inverter.   4/0 cable is not rated for that much current,   but  the battery voltage would probably crash,  in short order at that current.

    Please tell us more about your system.

    As noted,  above,   a  4 KW, inverter needs a lot of current at 50 - 75% load.   Why do you need such a large inverter,  on a 12 V battery bank?   If you need close to this amount of power for any length of  time,  at all,   you would be better served by a 48 V system,   and so on   ...

    Back to work here,   Others will chime in.   Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • BB.BB. Super Moderators, Administrators Posts: 31,629 admin
    Generally, I would suggest an 1,200 to 1,800 Watt maximum AC inverter for a 12 volt system... 4,000 Watts is, as Vic says, 400 Amps... And 8,000 Watt surge, that is ~800 Amps.
    • 1.8 Amps * 12 volts = ~22 Watts Tare Losses...
    • 22 Watts * 24 hours per day (if left running 24x7) = 582 WH per day
    That is almost 1/2 the amount of energy to run a full size 120 VAC refrigerator (around 1,000 to 1,500 WH per day typical).

    If you only need a few minutes of ~4,000 Watts (running a winch or similar)--It could make sense.

    If, however, you want to run loads for many hours per day, usually your loads are much less... Say 5 hours per night, 800 AH @ 12 volt battery bank, using 25% capacity overnight (2 nights, 50% max planned discharge):
    • 800 AH * 0.25 = 200 AH used
    • 200 AH / 5 hours usage = 40 Amp average load (for 5 hours)
    • 40 Amps * 12 volts = 480 Watt average load on 120 VAC inverter
    When we talk about "balanced" system design... First design the loads (for maximum efficiency), then size the battery bank to support those loads (average Watts/Amps, peak Watts/Amps, hours per day of use)... Then design the solar/genset/AC power charging needed to support those loads. All of those play well together. A very large inverter/loads will drain the battery bank quickly--Then need a lot of solar/charging to refill for the next day's use...

    What are you looking at for a charger? Another solar charger? An AC inverter for Genset or Grid use?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • MEK1954MEK1954 Registered Users Posts: 23 ✭✭
    I have a 4kw generator hardwired to 2 dedicated outlets so I can run my living room and part of my kitchen when the power goes out, so that's where I started, I am not sure what my usage will be at this point, I started this with the intention of expanding if I get enough solar power to to make it worth the cost so that's why the big inverter. 8 days of solar was on my electric bill and it saved 40.00 and that was enough to give me the solar fever.  
    Basically what I am asking is, is my solar panels (4x 195w panels) enough to maintain my battery's (4x 200 amp) The battery's get run down to about 60% and charged up to 85% on the average +-10%.
    And my issue with the battery charger is most I see are automatic 2/6/12 amp and it seams like charging 4- 200 amp battery's with 6 amps is no better then a trickle charger, so I was asking what recommendations you have.
  • MichaelKMichaelK Registered Users Posts: 198 ✭✭✭
    Lots of problems here, with poor wiring choices, poor equipment selections.  But, it's fixable. 

    Your biggest single problem is sticking with 12V.  That was poor judgement.  12V is for toys, automotive equipment, and small items.  The main reason is amperage.  Let's say you put a 2000W load on your inverter.  At 12V, 2000W is 2000W/12V = 167amps.  The 1/0 wire you have connecting your batteries to the inverter is only rated for 125A.  Use this chart....
    So, the wire you installed can't even safely handle a small fraction of what your inverter would demand with a full load.

    The second problem is 4 batteries in parallel.  They will be hard to balance, and hard to charge.  Although your AGM batteries have max charge rate of 52A, more likely they would be most happy charging at 20-30amps.  But 20-30A X 4 batteries in parallel is 80-120A, far above what your controller can handle.

    Your solar array is actually too small for your battery bank.  You are likely to get (195W X 4 panels)/13V charging = 60A.  That's the theoretical maximum.  On regular days, don't expect to see 51-52A, right at noon.  That might be good for charging 2 batteries, not 4.

    The good news though is that you have four batteries that can be re-wired to 48V, and an MPPT controller that can charge a 48V bank.  With a single string of batteries at 48V, that same 2000W load would now only need 2000W/48V= 42A instead of 167.  You just need a 48V inverter.  I'm partial to Schneider, and Schneider makes a nice 48V Conext unit.
    This is a quality whole-house inverter designed to be hard-wired into your home's mail service panel.  It does not have NEMA plugs.  What it does have is dual split-phase 120/240VAC house current, and a built in charger, that can be wired directly into your generator.  So, while this might be more expensive than some other inverters, you don't have to add a separate charger.

    With a 48V bank you'll want to charge that at 20+A, so the math works out to be 20A X 50Vcharging X 1.25 fudge factor = 1250W of panels.  If you get four more of your 195W panels, you'll get {(195W X 8 panels)/50V} X 0.8 fudge factor =25A, right in the ballpark.


    System 1) 15 Renogy 300w + 4 250W Astronergy panels,  Midnight 200 CC, 8 Trojan L16 bat., Schneider XW6848 NA inverter, AC-Delco 6000w gen.
    System 2) 8 YingLi 250W panels, Midnight 200CC, three 8V Rolls batteries, Schneider Conext 4024 inverter (workshop)
  • PhotowhitPhotowhit Solar Expert Posts: 5,565 ✭✭✭✭✭
    MEK1954 said:
    Basically what I am asking is, is my solar panels (4x 195w panels) enough to maintain my battery's (4x 200 amp) The battery's get run down to about 60% and charged up to 85% on the average +-10%.
    It's always hard to critique someone else's system without knowing why some things are selected. Also Someone in the Pacific North West who might get 1 1/2 hour of direct sunlight on average during rainy season and someone in the Southwest who gets 7+ hours of direct sunlight throughout the year will require different system. 

    To directly answer this question, For systems which are cycled daily, we usually recommend at least 10% of the battery capacity available from the solar array at their maximum point in time. So for a 800 amp hour 12 volt battery bank, that would be about 80 amps. Your 780 watts array, is likely to produce only 600 watts at any one time. This is the difference between Standard Test Conditions and Normal Operating Cell Temperature conditions (STC vs NOCT) so 600 watts divided by 12 volt = 50 amps. So this would be less than I would recommend. If you have daily loads this will detract from the ability of the array to provide charging and should further enlarge your array to cover that... So if you have no daily loads something like a 11-1200 watt array would be needed. If you are running a fridge, figure another 200 watts of array. I'm just making rough estimates. Just your inverter running without load is 20+ Watts and if that is a 'quiet/sleep mode' that it draws 20ish watts than when in use it may double or more.

    In reality, charging is done at 13-15 volts in general, so even worse than I'm suggesting!

    For weekend use, generally you can drop that to 5% of the battery capacity. Again this will vary by your solar insolation. You can go to PVWatts web site to figure out your average daily exposure, Skip most of the info there as it's designed for grid tied use, add your location and follow through to the end and it will give rough estimates of the available hours of direct sun light for each month of the year.

    https://pvwatts.nrel.gov/

    MEK1954 said:
     The battery's get run down to about 60% and charged up to 85% on the average +-10%.

    I don't know how you are measuring this? If you are using voltage, It is likely you are much farther apart than you think. Voltage is not a reliable way to measure your state of Charge (SOC) when a system is in operation. When charging your system voltage will always be higher than the batteries resting voltage, when discharging it will usually be lower than resting voltage.

    In general if a battery is left below 80% for any legnth of time it will begin sulfating.

    I understand at times it's necessary to have a large inverter,  starting large well pumps for instance. Sometimes it's also nice if you plan on expanding your system later and don't want to buy another inverter later. So I understand there are reasons.

    In addition, there are reasons to have multiple strings of batteries, but it's very difficult for them to share the load and charging. Something many have found out over time. They tend to work fine for a couple years and you don't notice the uneven charging and discharging. We mostly just want to help you with this information.

    In general higher system voltages help with this. I know you have a 12 volt system currently and replacing your inverter would not be cheap. But something too consider, particularly NOW. If you will need to replace your charge controller now to reach 80 amps delivery, understand that if you went to 24 volts, the same power (wattage) could be done with your existing charge controller as it would only need to deliver 40 amps at 24 volts to service a 400amp 24 volt bank. So you could add that money toward your new inverter. Move to a 48 volt system and it's only 20 amps for a 48 volt 200 amps battery bank!

    FWIW - I ran my 16x60 mobile home with a fridge and window air conditioner for 7 years on a 1800 watt 24volt inverter. I did have to make some minor adjustments, I tried not to run the front loading washing machine at the same time as the window air conditioner as when the fridge would pop on sometimes it would create too large a draw on the inverter and it would shut down for safety reasons. But it was very 'doable'. Even ran a table saw from time to time, but with everything else shut off typically.
    MEK1954 said:
    All the battery's join at one point with 4ga wire and 1/0 ga from the batt to the inverter, with no power being used the inverter draws 1.8 amps.
    If you think my components are not very well balanced, what are your concerns?
    Others have suggested that the wiring is too small for this inverter. Let me show you...

    4000 watts at 12 volts would require 4000watts/12volts=333amps

    1/0 wire can handle about 230 amps;

    Conductor Ampacity - InstrumentationTools
    4/0 would be required.
    MEK1954 said:
    And my issue with the battery charger is most I see are automatic 2/6/12 amp and it seams like charging 4- 200 amp battery's with 6 amps is no better then a trickle charger, so I was asking what recommendations you have.

    It looks like you are looking at maintainers, There are chargers out their Iota is one brand which are designed to charge deepcycle batteries, here's one that's 55 amps from the forum's sponsor. (They make larger) I think they are pretty cheap, but you might find it cheaper elsewhere;

    https://www.solar-electric.com/iota-engineering-dls-55-x-battery-charger.html

    Alot of people try to charge in the morning with the generator and allow the solar array to do the finaly 15-20% as the battery accepts less current as the reach fully charged. 
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • MEK1954MEK1954 Registered Users Posts: 23 ✭✭
    That was a lot of very good information, very informative and I thank you very much, I see now I have to make a few changes.
    Mark
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