spacebass: What solar panels for 36 volt battery bus

SystemSystem Posts: 75 admin
edited July 19 in Solar Beginners Corner #1
This discussion was created from comments split from: 24v panel with 12v battery.

From SpaceBass:

BB. said:
We need some more details... How big of solar array (Watts), what is the coldest temperature in your area, what voltage battery bank (12/24/36/48 volt), and what type battery (flooded cell, AGM, etc.)? Do you plan on making your system larger? Do you want "simple" or "remote monitoring" and other features?

-Bill
Bill, if your 'details' is directed at me, I intend to buy a 60 amp multi voltage mppt controller , I have 4 x 330 watt 24 volt mono panels I want to use , 2 x 210 Ah 12 volt deep cycle wet batteries I want to add a third for 36 volts.haven't worked out the inverter yet. I live in Thailand 30'. Cannot find a 36 volt inverter.
https://s.lazada.co.th/s.Ze4LI

Comments

  • spacebassspacebass Registered Users Posts: 59 ✭✭
    What panels would you use with 36 volt mppt controller ?
  • BB.BB. Super Moderators, Administrators Posts: 29,706 admin
    We need some more details... How big of solar array (Watts), what is the coldest temperature in your area, what voltage battery bank (12/24/36/48 volt), and what type battery (flooded cell, AGM, etc.)? Do you plan on making your system larger? Do you want "simple" or "remote monitoring" and other features?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 29,706 admin
    Spacebass,

    I will move your Q&A to its own thread... It should be less confusing--Especially if Tordfish comes back.

    There are some 36 volt AC inverters out there... I think 36 volts battery bus was sort of common for larger (private?) boats in decades past.

    https://www.amazon.com/36-volt-inverter/s?k=36+volt+inverter (USA search results)

    For off grid solar power, 12/24/48 VDC battery is much more common... 36 volts is sort of a 1/2 step in the bus voltage progression and you may not want to paint yourself into a corner (find a 36 volt AC inverter, but 5+ years down the road, hard to find replacement). Also, if you need a 36 volt AC battery charger (utility/genset charging)--Your 36 volt charging choices are going to be a bit thin.

    Your MPPT (English translation) MPPT charge controller link has some nice documentation:
    • 12v system can receive from DC 18v-DC 150v
    • 24v system can receive from DC 34v-DC 150v
    • 48v system can receive from DC 65v-DC 150v
    However, the basic specification does "gloss over" the realities of solar panels... The "24 volt panel" generally have Vmp in the range of 30-36 volts at 25C cell temperature (room temperature) ... But we need to know your "exact" Vmp-std rating for your panel to figure out the hot derating (and for cold climates, Voc-std for cold deratings).

    For example, in warm to hot weather, yorr Vmp falls from 30 volts to ~24 volts (almost a 20% drop)... And your MPPT controller really wants to be 1.3x your battery bank voltage... When this is all thrown together, your Vmp-array-std rating should be a minimum of:
    • 30 volts battery charging * 1.3 minimum MPPT suggested operating point (ideal) * 1/0.80 Vmp-hot derating = 48.75 volt Vmp-array-std
    So, at the very least, for a 24 VDC battery bus, you should put two of your "24 volt" panels in series.

    If you had a 36 volt battery bus:
    • 45 volt batt charging * 1.3 mppt minimum voltage * 1/0.80 hot panel deratring = 73.125 Vmp-array-std minimum
    And here is where Vmp=30 volts vs Vmp=36 volts (for your 330 Watt panels) make a difference... 2x30v=60 volt Vmp-array-std (not ideal for MPPT on 36 volt bus) vs 2x36 volt = 72 volt array (close enough to work).

    And then you have the issue of 3xVoc-cold for the panels... In cold regions, that could be an issue in subzero conditions (Voc-array-cold>150 VDC max input)--But you are in Thailand, so probably not an issue.

    "Higher voltage" Solar Panels can be kind of a pain when matching to battery bank and Vpanel-max ratings for charge controllers...

    Details matter here--

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • spacebassspacebass Registered Users Posts: 59 ✭✭
    edited July 19 #5
    Thank You for comprehensive answer I need to go back to school for a long time !! One of the main reasons I am moving to the Applegreen mppt controller is that it is about 8% overall more efficient than the Epever Tracer 40 amp and handles more input volts Iand amps. I looked at 36 volts as a way of increasing battery capacity but does not seem practical .My novice experience with the Epever Tracer 40 amp is that it seems to do good mppt uprating of amps but 40 amp? In the hand book it says : ' 24 volt Best Configuration 1 panel Maximum 2 panels'  and when I had 4 panels on it the 60 amp breaker between controller and batteries was breaking.  On the face of it why would anyone buy a 40 amp controller for 1 panel?
    The Apple green controller does cost nearly twice as much as the Epever Tracer there is a 30 amp version plus 50% on Epever.
    N
    I have 2 x 24 volt panels in series should I add a third in series To get optimum voltage in the heat ?

  • BB.BB. Super Moderators, Administrators Posts: 29,706 admin
    Still need the nameplate voltages/currents for your proposed panels...

    Roughly, 2x battery voltage --- Probably ideal for efficiency. The higher the voltage difference from Array to Battery bank, the (a little bit) less efficient MPPT charge controller--But I would not make a big deal out of that "loss of efficiency" (a couple of percent difference).

    If you have a "long wire run" from array to charge controller+battery shed, having higher Vmp-array allows you to use smaller diameter wiring for the array/install array farther away.

    Other issues--When you have 3 series x 2 parallel strings, you do not need inline fuses/breakers for array safety. With 2 series x 3 parallel, you should have series protection fuses/breaker (typically ~15 amps--Check the panel specifications) with a combiner box (more hardware, more expenses).

    Having a breaker/switch on the array and on the Controller to Battery bank allows you to turn on/off the array (and controller) while working the system. Note: Turn on Battery first, and turn off battery last (turn on array last, turn off array first). You want the charge controller running off of battery power before solar array power. The battery power configures the controller for 12/24 volts and protects against solar array "voltage surges to the output" that could damage the charge controller.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • littleharbor2littleharbor2 Solar Expert Posts: 1,440 ✭✭✭✭
    Never heard of Apple Green brand controller but if it will do 48 volts you can have a much larger (double) solar array and battery bank than a 24 volt system.

    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.

  • spacebassspacebass Registered Users Posts: 59 ✭✭
    edited July 20 #8
    BB. said:
    Still need the nameplate voltages/currents for your proposed panels...

    Roughly, 2x battery voltage --- Probably ideal for efficiency. The higher the voltage difference from Array to Battery bank, the (a little bit) less efficient MPPT charge controller--But I would not make a big deal out of that "loss of efficiency" (a couple of percent difference).

    If you have a "long wire run" from array to charge controller+battery shed, having higher Vmp-array allows you to use smaller diameter wiring for the array/install array farther away.

    Other issues--When you have 3 series x 2 parallel strings, you do not need inline fuses/breakers for array safety. With 2 series x 3 parallel, you should have series protection fuses/breaker (typically ~15 amps--Check the panel specifications) with a combiner box (more hardware, more expenses).

    Having a breaker/switch on the array and on the Controller to Battery bank allows you to turn on/off the array (and controller) while working the system. Note: Turn on Battery first, and turn off battery last (turn on array last, turn off array first). You want the charge controller running off of battery power before solar array power. The battery power configures the controller for 12/24 volts and protects against solar array "voltage surges to the output" that could damage the charge controller.

    -Bill
    Bill, I am getting 70 volts on Tracer mt 50 remote 2 panels in series, was showing 80 volts with 4 panels 2 strings.
    Panel Spec : Pmax 340,Vmp 38.15,Imp 8.91,Voc 46.26, Isc9.45 ,efficiency 17.5 %
    No long runs about 15 feet panels controller I have 40 amp breaker in panel supply , I know too big .
    It is 0800 I have 63 volts from panels this will rise to around 70 volts. 
    This system is up and running in the new system referred to I was going to utilise the 2 removed panels and buy the other bits , i.e. upgrade the mppt controller in this system to applegreen and move epever tracer to new system for inverter air con at night only .
  • PhotowhitPhotowhit Solar Expert Posts: 5,023 ✭✭✭✭
    spacebass said:
    …. when I had 4 panels on it the 60 amp breaker between controller and batteries was breaking....
    Was this a DC rated breaker? How many amps were you passing through it?
    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
  • spacebassspacebass Registered Users Posts: 59 ✭✭
    edited July 24 #10
    Photowhit said:
    spacebass said:
    …. when I had 4 panels on it the 60 amp breaker between controller and batteries was breaking....
    Was this a DC rated breaker? How many amps were you passing through it?

    Hi this is an auto audio DC breaker marked battery /accessory on the poles. I don't know how many amps are passing through the breaker when it breaks but I believe the 40 amp tracer AN controller is somehow tripping the breaker when it gets over spec'd volts or amps going on because it says in the handbook it will disconnect accessories when this happens and then reconnect them when normality returns but of course it cannot reconnect a breaker. With regard to this disconnection for what I believe is too many panels (4x24volt) for the controller to handle even though it looks OK on paper running with two panels it does not happen.
    Now a new circumstance where the breaker goes in the day with two panels connected after a long period of intense sunshine  leaving on the tracer MT- 50 remote screen a full battery icon and 27 volts + in the battery , I believe the tracer controller has tripped the 60 amp breaker because of too much something the point being that it may have legitimately tripped the breaker but cannot restore the system back to working as it presumably could if the breaker was not there.
    I am ditching this Tracer controller I think it is good from an mppt charging  point of view but cannot handle the tropical sun.
    I am going to buy an Applegreen mppt controller costs nearly twice as much as the Tracer.
    https://s.lazada.co.th/s.ZVlUJ

  • mcgivormcgivor Solar Expert Posts: 3,166 ✭✭✭✭✭
    spacebass said:
    Photowhit said:
    spacebass said:
    …. when I had 4 panels on it the 60 amp breaker between controller and batteries was breaking....
    Was this a DC rated breaker? How many amps were you passing through it?

    Hi this is an auto audio DC breaker marked battery /accessory on the poles. I don't know how many amps are passing through the breaker when it breaks but I believe the 40 amp tracer AN controller is somehow tripping the breaker when it gets over spec'd volts or amps going on because it says in the handbook it will disconnect accessories when this happens and then reconnect them when normality returns but of course it cannot reconnect a breaker. With regard to this disconnection for what I believe is too many panels (4x24volt) for the controller to handle even though it looks OK on paper running with two panels it does not happen.
    Now a new circumstance where the breaker goes in the day with two panels connected after a long period of intense sunshine  leaving on the tracer MT- 50 remote screen a full battery icon and 27 volts + in the battery , I believe the tracer controller has tripped the 60 amp breaker because of too much something the point being that it may have legitimately tripped the breaker but cannot restore the system back to working as it presumably could if the breaker was not there.
    I am ditching this Tracer controller I think it is good from an mppt charging  point of view but cannot handle the tropical sun.
    I am going to buy an Applegreen mppt controller costs nearly twice as much as the Tracer.
    https://s.lazada.co.th/s.ZVlUJ



    If the Tracer is 40A it's output would be limited to that current, so the problem probably lies in the beaker. Automotive breakersare not rated for continuous high current, they are also thermal which means if used in hot climates their trip value will be reduced, they also have a tollerance + or - 10% for example. One 10A breaker I have will trip at < 7A if the ambient is 40°C, at 35°C it's fine, there are electromagnetic types which are not affected by temperature to the same degree. 

    Has the current actually been measured and dose the breaker get hot?
    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.
  • littleharbor2littleharbor2 Solar Expert Posts: 1,440 ✭✭✭✭
    edited July 24 #12
    Automotive audio breaker, is it rated for 12 volts and you are running how many volts through it? Could be a problem there.

    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.

  • spacebassspacebass Registered Users Posts: 59 ✭✭
    Automotive audio breaker, is it rated for 12 volts and you are running how many volts through it? Could be a problem there.

    A lot of these breakers state 12v 24 v but it would not surprise me if they were lying.

  • spacebassspacebass Registered Users Posts: 59 ✭✭
    edited July 24 #14
    mcgivor said:
    spacebass said:
    Photowhit said:
    spacebass said:
    …. when I had 4 panels on it the 60 amp breaker between controller and batteries was breaking....
    Was this a DC rated breaker? How many amps were you passing through it?

    Hi this is an auto audio DC breaker marked battery /accessory on the poles. I don't know how many amps are passing through the breaker when it breaks but I believe the 40 amp tracer AN controller is somehow tripping the breaker when it gets over spec'd volts or amps going on because it says in the handbook it will disconnect accessories when this happens and then reconnect them when normality returns but of course it cannot reconnect a breaker. With regard to this disconnection for what I believe is too many panels (4x24volt) for the controller to handle even though it looks OK on paper running with two panels it does not happen.
    Now a new circumstance where the breaker goes in the day with two panels connected after a long period of intense sunshine  leaving on the tracer MT- 50 remote screen a full battery icon and 27 volts + in the battery , I believe the tracer controller has tripped the 60 amp breaker because of too much something the point being that it may have legitimately tripped the breaker but cannot restore the system back to working as it presumably could if the breaker was not there.
    I am ditching this Tracer controller I think it is good from an mppt charging  point of view but cannot handle the tropical sun.
    I am going to buy an Applegreen mppt controller costs nearly twice as much as the Tracer.
    https://s.lazada.co.th/s.ZVlUJ



    If the Tracer is 40A it's output would be limited to that current, so the problem probably lies in the beaker. Automotive breakersare not rated for continuous high current, they are also thermal which means if used in hot climates their trip value will be reduced, they also have a tollerance + or - 10% for example. One 10A breaker I have will trip at < 7A if the ambient is 40°C, at 35°C it's fine, there are electromagnetic types which are not affected by temperature to the same degree. 

    Has the current actually been measured and dose the breaker get hot?
    If the Tracer limits current to 40 amp as I believe it is supposed to and states in handbook it disconnects things if electricity goes out of spec why do people need a breaker ? It is removing some of the utility of the controller i.e. the ability to reset operation after cloedown.sfter spike.
  • EstragonEstragon Registered Users Posts: 4,186 ✭✭✭✭✭
    The breaker is there to protect wire in a fault condition, most likely of which being a short in the controller.  Absent the breaker, 100's to 1000's of amps from batteries could flow across the short.
    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
  • spacebassspacebass Registered Users Posts: 59 ✭✭
    Estragon said:
    The breaker is there to protect wire in a fault condition, most likely of which being a short in the controller.  Absent the breaker, 100's to 1000's of amps from batteries could flow across the short.
    Does that just mean the controller is toast ?
  • EstragonEstragon Registered Users Posts: 4,186 ✭✭✭✭✭
    If the controller is shorting, yes.
    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
  • BB.BB. Super Moderators, Administrators Posts: 29,706 admin
    Or if not exceeding 40 amps, a bad breaker.

    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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