few questions about solar (a newbie)

Nabiru3Nabiru3 Posts: 3Registered Users
edited April 22 in Solar Beginners Corner #1
Hello guys
my name is Nabil, and I am new to the solar power world and I have got few simple questions (just to be on the safe side)

question 1) I have got 1 MPPT morningstar tristar 30A charge contoller and 2 LG 315 panels (around 33Vmpp each) and 2 12v batteries wired in series (24v system) now I have the options of both wiring the solar panels in parallel or in series (cause the charge controller can take up to 30A and 150V). now (as the old legend says) if you have a 24v battery bank you should connect it to a 24v nominal panel array, right ? BUT, with an MPPT controller it is different as it can handle large volts to make them charge lower battery nominal voltage (boost current feature) so now i am confused as I can connect both panels in either way and still get the same output, so which method should I go with series or parallel ???
(btw, in the manual it says it is better to charge low nominal voltage battery using a higher nominal voltage panel(s) NOT the opposite though)

question 2) My 24v system inverter(which is indian btw) has a battery type switch in the back where it says I should either choose (Tubular or Flat plate), I know that Lead Acid batteries are categorized as (VLA & VRLA) and some VRLA types are GEL and AGM batteries, but I really don't know what kind of battery classification (Tubular and Flat plate) is. so if you please tell my which battery type option i should go with ? btw, my batteries are of type (Trojan VRLA AGM 12V) 

question 3) (I am really sorry this is being overly annoying :# )  I have a 0.5hp (370w 1.7a rated) domestic water pump, if we say I run it for 1 straight hour on a 300AH 12v battery(which 100% full), how much of battery juice I will get remaining (considering both the continuous running wattage and the starting Amp (LRA) consumption of the pump motor)

Thanks in advance for any help provided 

Comments

  • PhotowhitPhotowhit Posts: 4,483Solar Expert ✭✭✭✭
    on question 1, you should hook the panels up in series, the MPPT charge controller needs about 30% higher voltage than the charging voltage.

    On Question 3, It sounds like you will be running a 24 volt battery bank, so I think you have something out of sync here...

    ... but it's a bit of a trick question, assuming the load is a AC load, you will also have the inverters inefficiency to consider. The inverter will use 7 to as much as 20% more energy than the load. so I'll use 420watts for the total load. So 420watts at 12 volts will be about 420/12=35 amps per hour. Now we run into another problem. Batteries are rated based on a discharge rate of 1/20th or their capacity (C20). If you draw current off faster than 1/20th, their effective capacity is lower. This changes by battery type and plate design. This is called Peukert's Law, This might help explain it...

    https://www.batterystuff.com/kb/tools/peukert-s-law-a-nerds-attempt-to-explain-battery-capacity.html

    So I'd give a rough guess of around 255-260 Amphours at C20.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • mcgivormcgivor Posts: 1,652Registered Users ✭✭✭✭
    edited April 22 #3
    Welcome to the forum Nabil

    With question 1, being that the panels are 24V nominal panels it would be possible to connect either way, in theroy, but series would probably be better to allow more headroom for the MPPT to work it's magic. Another consideration is high ambient temperatures tend to lower the output voltage so again series would probably work better. Input your relevant information in the fields of this string calculator  http://string-calculator.morningstarcorp.com/  this is the best way to find tho optimum arrangement.

    Question 2. Flat plate would be most likely the setting for regular Trojans, can you post a link to the exat battery? 

    Question 3. This is tricky question to answer because although the pump is rated at 1.7A at 230V, it is an inductive load, so power factor comes into play, which will increase the draw from the system. From experience with a 1/2 Hp pump, the draw should be approximately 24A at 24V nominal lower if the voltage is higher and higher if the voltage is lower. The trick is to run the pump once the battery is fully charged, this way the panels will supply the bulk of the current requirements allowing the batteries to recover afterwards. So let's use 24A at 24V as a guide, that would equate to 24Ah, so if you were to pump after the sun has set, the battery which has a usable capacity of 150 Ah (to keep within the 50% state of charge for longer battery life ) 150-24=125Ah remaining. If pumping is done as suggested when the charging is complete, the capacity would be back after a few hours or less, leaving the nominal capacity available. This method is referred to as opportunity loads, using production that would otherwise be wasted. 

    Hope this helps, others will surely have valuable input, there are some very helpful members here who will offer advice, good luck.
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • HorseflyHorsefly Posts: 301Registered Users ✭✭✭
    edited April 22 #4
    mcgivor said:
    ....
    From experience with a 1/2 Hp pump, the draw should be approximately 24A at 24V nominal lower if the voltage is higher and higher if the voltage is lower. 
    Hey @mcgivor, I'm not sure what the difference might be between your 1/2 HP pump and mine, but my 1/2 HP well pump pulls about 60A continuous from my 24V battery bank.  

    EDIT: I just went back and looked at my notes from last summer, and it looks like it was actually more like 57A most of the time.
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 4 x Vmax XTR12-155 12V, 155AH batteries in a 2x2 24V 310AH bank.
  • mcgivormcgivor Posts: 1,652Registered Users ✭✭✭✭
    Horsefly said:
    mcgivor said:
    ....
    From experience with a 1/2 Hp pump, the draw should be approximately 24A at 24V nominal lower if the voltage is higher and higher if the voltage is lower. 
    Hey @mcgivor, I'm not sure what the difference might be between your 1/2 HP pump and mine, but my 1/2 HP well pump pulls about 60A continuous from my 24V battery bank.  

    EDIT: I just went back and looked at my notes from last summer, and it looks like it was actually more like 57A most of the time.
    Is your pump 120V? in India the voltage would be double, or 230V so the current would halved, or there abouts, which would equate to being about the same, yas, no? 

      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • HorseflyHorsefly Posts: 301Registered Users ✭✭✭
    I'm talking about the current out of the battery, not the AC current. I thought you were too.  That would be (or should be) independent of what the output voltage was for the Inverter, right?
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 4 x Vmax XTR12-155 12V, 155AH batteries in a 2x2 24V 310AH bank.
  • EstragonEstragon Posts: 2,229Registered Users ✭✭✭✭
    If it's [email protected], that would be [email protected]?
    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
  • EstragonEstragon Posts: 2,229Registered Users ✭✭✭✭
    edited April 22 #8
    If it's [email protected], that sounds close-ish to what I see on my (240vac) submersible in the lake ([email protected]) into pressure tanks.
    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 Posts: 7,612Solar Expert ✭✭✭✭
    1) does your battery have caps to add distilled water to ?   if so, it's very likely flat plate.

    2) wire the panels in series, and let the Controller manage it,  easy.

    3) Pump.   Watts AC = V x A. then convert the watts to DC 24V and you will learn how many amps at 24V the battery must supply

    Here's a power chart for pumps.   My pump, 240V 3wire, 1/2 hp, consumes about 1,000w exactly when running.  At 24V that would be 41 amps, plus about 15% more for internal inverter losses


    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 ,

  • mcgivormcgivor Posts: 1,652Registered Users ✭✭✭✭
    Horsefly said:
    I'm talking about the current out of the battery, not the AC current. I thought you were too.  That would be (or should be) independent of what the output voltage was for the Inverter, right?
    You are  correct the battery current would be based on the power requirements not the voltage of the pump, for a given power, the battery if the same voltage, would be  equal current. My mistake,  credit to you for the clarification. 
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • Nabiru3Nabiru3 Posts: 3Registered Users
    Great thanks for all of your answers which helped me a lot in understanding some of the basics.


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