Is my solar power setup working efficiently?

DzefaDzefa Registered Users Posts: 18 ✭✭
edited March 8 in Solar Beginners Corner #1
Hello everybody,

I have designed the solar setup for my RV and got this installed by a company this weekend. Since the setup is complete I am now testing/trying to understand everything to make sure everything is working properly. My setup is as follows:
  • 2x 200W Mono solar panels wired in series (See specifics below)
  • Epever Tracer 3210AN 30 amp (incl MT50)
  • 2x 200 Ah AGM batteries
  • Aili battery monitor
My MT50 screen shows the following. This is at full morning sun in Turkey today.

PV.                             Battery                          Load
46.5V.                         14.9V                           14.9V
0.7A                             2.0A.                            0.1A

Now I have 1 major and 1 bonus question:
  • Based on this info I assume that the batteries are charging at 2Amps per hour. In great conditions here we have 6 hours of full sun a day. Does this mean that the batteries will maximum charge 12 A/h per full day? If so, it seems to me that something should be wrong. 400W of solar power should be able to power way more than 12 A/h per day. Or is this normal? Or am I interpreting the numbers wrong?
  • Bonus question: For my Aili battery monitor I should first fully charge the batteries and then set the monitor at a 100% (to calibrate). However, how can I know when they are fully charged? I know the table showing 12.7+ is 100% full. However, till 7PM they are charging of the solar panels. Should I get up in the middle of the night to let them "cool down" and check the voltage then? Or is there another way to see if they are full?

Thank you so much everyone!

Solar panel info
Maximum Power (Pmax)200 Wp
Open Circuit Voltage (Voc)23,80 V
Maximum Power Voltage (Vmp)20.70 V
Short Circuit Current (Isc)9,99 A
Maximum Power Current (Imp)9,79 A
Working Temperature Range-40 o C ~ +85 o C

Comments

  • mcgivormcgivor Solar Expert Posts: 3,815 ✭✭✭✭✭✭
    edited March 8 #2
    Welcome to the forum 

    The battery will only accept current if not charged, judging by thr voltage stated, 14.9V, I would think you are overcharging the AGM batteries, typically they require a lower rate of around 14.3V. This is important because AGM will vent excess gas produced which will result in premature failure, check the specifications from the manufacturer. A remote temperature sensor should be used to reduce charging voltage during hot periods or increase during cold, 25°C is the mean normal temperature.

    The full potential of the array will only be revealed when the batteries are in a partial state of charge, the amount of energy produced on any given day will depend on the depth of discharge and the amount of available sun. Normally the panels will produce around 75% of rated power perfectly aligned, in high ambient temperature it could be even less. 

    When a battery is not discharged overnight there would be a short charge to recover any self discharge along with what the controller consumes, usually very little, if it were discharged to 12.2V for example, the current will gradually increase as the sun rises and reaches peak at noon.

    You should start with a system designed for prospective loads to ensure its capable of supporting them, it may be a good idea to supply these details before making costly mistakes, or were such details supplied to the installer? 

    Something is wrong with the settings, don't allow this to continue, disconnect the PV then battery to prevent further damage, the reason the 2A is seen is because the voltage is too high, generating heat, I would suspect the batteries are warm to the touch. 




    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • DzefaDzefa Registered Users Posts: 18 ✭✭
    Thanks for the welcome and the mega fast reply McGivor!

    The manufacturer provides the following data sheet of the batteries: http://www.beaut.nu/fileuploads/lwd_agm200-12.pdf

    It states that the boost charge should me 14.6 - 14.8V. I am using the below settings currently on the Epever MPPT:
    • Batt. type: User
    • Batt. AH: 400AH
    • Temp comp coeff: -3mv/C/2v (unchanged)
    • Rated voltage: Auto
    • Over volt Disc. 16.0V
    • Charge Limit: 15.0V
    • Over volt rec: 15.0V
    • Equal charge: 14.6V
    • Boost Charge: 14.6V
    • Float Charge: 13.8V
    • Boost Rec: 13.2V
    • Low volt Rect: 12.6V
    • Under volt Rect: 12.2V
    • Under Volt warn: 12.0V
    • Low volt Disc: 11.1V
    • Discharge 10.6 V
    • Equalize time: 120 min
    • Boost time: 120 min
    Which of these settings do you recommend I should change?

    "The full potential of the array will only be revealed when the batteries are in a partial state of charge, the amount of energy produced on any given day will depend on the depth of discharge and the amount of available sun. Normally the panels will produce around 75% of rated power perfectly aligned, in high ambient temperature it could be even less. "

    Should I then at night run all my appliances to discharge the batteries, and then the next day see what numbers show on the MT50? 

    You should start with a system designed for prospective loads to ensure its capable of supporting them, it may be a good idea to supply these details before making costly mistakes, or were such details supplied to the installer? 

    The whole system is installed by a experienced RV building company. They connected all the 12v devices and inverter as well. 

    Something is wrong with the settings, don't allow this to continue, disconnect the PV then battery to prevent further damage, the reason the 2A is seen is because the voltage is too high, generating heat, I would suspect the batteries are warm to the touch.

    I checked it just now, luckily the batteries are not warm.
  • DzefaDzefa Registered Users Posts: 18 ✭✭
    Also, shouldn't the PV ampere be higher than 0.7 even though the batteries are full? Or is this number also automatically lowered when the batteries are full?

    I understand the battery A being low at 2.0 because they are full, however, I would expect the PV to still show higher A. Or is this not the case? 
  • mcgivormcgivor Solar Expert Posts: 3,815 ✭✭✭✭✭✭
    The settings are for the most part according to the specifications for cyclical use 14.6-14.8V, you have 14.6V boost, which is referred to in most controllers as bulk/absorption, float is at the highest level, 13.8V which is fine because there is no charging once the sun sets. Since AGM generally  don't need equalization, the value is set for the same as regular charging, if equalization can be disabled by entering a time of zero minutes, I would do so, just to eliminate the function which may be an unnecessary automatic monthly event.

    The Epever  settings can be customized with a PC  I believe, if so I would be inclined to narrow the charge limit to the maximum charging voltage of 14.8V and over voltage disconnect to 14.9V. The low voltage disconnect settings are to do with the load terminals, are there DC loads attached? If so  I would raise the low voltage disconnect to something a little higher, perhaps 11.8V, depending on what the loads are which will influence the normal voltage drop, the lighter the loads the higher the disconnect value and vice versa.

    One thing not mentioned is if there were loads present, or the inverter connected when seeing the 2A charging as the may be the idle of the inverter, the 14.9V battery voltage is the outstanding thing of concern.

    When batteries are fully charged they should have little to no charging current, but again any loads, including the inverter unloaded will draw something which will be displayed as charging current even though it not actually going to the batteries themselves but diverted.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • DzefaDzefa Registered Users Posts: 18 ✭✭
    Thanks McGivor! Luckily, I can easily adjust the parameters using the MT50 display. Based on your advice I want to make to following changes:

    • Equalize time: 120 min. --> NEW VALUE: 0
    • Charge Limit: 15.0V. --> NEW VALUE: 14.8V
    • Over volt Disc. 16.0V. --> NEW VALUE 14.9V

    Did I interpret this correctly?

    At the moment I registered those numbers there was no load (not on the MPPT and not on the batteries). Inverter was turned off. Maybe the battery was not fully charged, but nearly fully charged? How can i recognise from these numbers when the battery is fully charged?

    I turned of the solar panel array and quickly after that the battery Voltage dropped to 13.7, after this slowly still dropping. Do you recommend any tests I should do?

    Thanks again for the help!
  • mcgivormcgivor Solar Expert Posts: 3,815 ✭✭✭✭✭✭
    edited March 8 #7
    Because the charging voltage was elevated at 14.9V it is likely that it was overcharging, take a look see approach, don't hinge everything on what I have to say, there are others who may agree or disagree with what I've said and I'm fine with that. 

    There is however  fine line in determining the exact parameters required , narrowing the setpoints, as proposed and done, is in my opinion a good starting point, they will for the most part prevent damaging the batteries from overcharging, having said that, the most common reason for battery failure is cronic undercharging, hence the previous statement's reference to loads, particularly overnight.

    There is no point in  charging a battery bank just for the sake of it, unless for standby applications, thus knowing specific details on projected loads is vitally important to determine if the system will support the requirements and help others with recommendations.

    The settings, as changed, are what I would use, there are very knowledgeable people who will likely contribute to the discussion at a later time, I just happen to be the first to respond, being in a favorable time zone, so expect some evolution.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • DzefaDzefa Registered Users Posts: 18 ✭✭
    Thanks! Ill wait and see a bit what others have to contribute :)
  • PhotowhitPhotowhit Solar Expert Posts: 5,576 ✭✭✭✭✭
    So basics of battery charging;

    During charging, there are basically 3 stages of charging, Bulk, Absorb, and Float.

    BULK;
    First thing when charging starts you will be in bulk, the voltage rises from what ever the system voltage was to a set point, around 14.5 volts. At that point the Charge controller stops the voltage from rising. Higher voltage can damage sealed batteries.

    ABSORB;
    Once the battery hits the preset point the charge controller keeps it at that point. Your batteries are roughly 80% full. Flooded batteries will start accepting less current at 80-85% full AGM/Sealed may go a little longer before accepting less current.

    On many controllers you can set this point, Some will have different presets for Flooded, and sealed batteries, or flooded, AGM, and sealed batteries. 

    The charge controller has a couple ways to know when to switch to float, Most inexpensive Charge controller are just timed for 1.5-2 hours. Some will also see less current flowing through the charge controller and shut it down when minimal current is flowing through the controller. On more expensive charge controller. You can set battery capacity to give the Controller a better idea of when to stop. you can also set a longer Absorb time. Or set 'end amps' a amount of amps flowing through the charge controller to stop Absorb and switch to the final stage.

    FLOAT;
    Once the Controller has determined the battery is fully charged it reduces the voltage to a point where very little current is flowing to the battery. This will prevent the battery from over charging and heating up.

    While in 'Float' the charge controller watch for voltage drop, which would indicate a load. If the voltage begins to drop the charge controller will allow as much current to flow from the panels/array to compensate and maintain the voltage. If the voltage can be maintained, the load will in essence be running directly off the array/solar. If the voltage drops below the preset float voltage, the controller may start a whole new cycle if it stays there for a period of time.

    The system voltage drop you see at night when the sun goes down is the charge controller moving into a resting mode with no energy to contribute to the system.

    The morning voltage may reflect a load present that is effecting the voltage level. With sealed batteries, you would want to disconnect the battery from the system and allow it to 'rest' for a while to get an accurate idea of it's SOC (State Of Charge) from the voltage.

    So at;

    Dzefa said:
    My MT50 screen shows the following. This is at full morning sun in Turkey today.

    PV.                             Battery                          Load
    46.5V.                         14.9V                           14.9V
    0.7A                             2.0A.                            0.1A
    This it appears your batteries are at 'absorb' with the charge controller limiting the voltage and the battery limiting how much amperage it is absorbing. It should drop to 'Float' voltage, which appears to be set at 13.8.

    Dzefa said:
    Bonus question: For my Aili battery monitor I should first fully charge the batteries and then set the monitor at a 100% (to calibrate). However, how can I know when they are fully charged? I know the table showing 12.7+ is 100% full. However, till 7PM they are charging of the solar panels. Should I get up in the middle of the night to let them "cool down" and check the voltage then? Or is there another way to see if they are full?
    Based on the battery charging info, and if you are using a shunt based battery monitor. You can set it to 100% once the battery has dropped down to 'Float' state of charging. At Float the charge controller at the dropped voltage is not sending much current(amperage) to the battery, just enough to keep the voltage slightly elevated. It will allow additional current to flow if you apply loads to keep it at this float voltage, up to the limits of the solar array.

    Dzefa said:
    Based on this info I assume that the batteries are charging at 2Amps per hour. In great conditions here we have 6 hours of full sun a day. Does this mean that the batteries will maximum charge 12 A/h per full day? If so, it seems to me that something should be wrong. 400W of solar power should be able to power way more than 12 A/h per day. Or is this normal? Or am I interpreting the numbers wrong?
    Once you have reach float you could add loads to the system to see how much wattage(power) is available. This will depend on the angle of the panels to the sun and how hot the panels get. 

    Normally a 400 watt array would max out around 300 watts, simply because they are tested for wattage without becoming 'Hot'. If they have a good bit of space under them so that there is some ventilation would be best.

    I would guess They would produce around 300/13.8= @ 21-22 amps, while in float. Indeed the system is likely to drop to a bit lower voltage as it nears max and you would see a higher current at a reduced voltage. Remember our basic equation;

    Amps x Volts = Watts.
    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.
  • BB.BB. Super Moderators, Administrators Posts: 31,684 admin
    edited March 8 #10
    Agree with McGivor, your battery(ies) are being over charged.

    Buried in the specs they say 2.4 to 2.45 volts charging (x6 cells = 14.4 to 14.7 volts)... I would go with 14.4 (or McGivor's 14.3 volts) charging.

    I think they are suggesting high(er) charging voltages for very quick charging to full. "Fast" and elevated 

    They also use -4 mV/C/Cell for temperature derating (not -3 mV).

    And you need to look at the battery charging current. When the batteries are truly discharged--They will take quite a bit of current (below, very roughly, 80% state of charge)--Otherwise known as "Bulk" charging or charging at the maximum rate the controller can output current. As Lead Acid (and AGM) batteries get closer to 100% state of charge, they naturally throttle back on current--Or the "Absorb" charging phase. The battery should gradually fall back to around 0.2% or 0.1% rate of charge (400 AH battery bank * 0.2% = 0.8 amps). At that point charging should be stopped and/or fall back to float charging (13.6 to 13.8 volts).

    No EQ charging, or 14.3-14.4 volt EQ charging for 4-8 hours once energy 6 months would not be harmful. For AGM batteries, there has been changing thoughts on the EQ question... From never EQ to EQ at absorb voltage setting once every 6 months for something like 8 hours to bring up any "weak" cells.

    Also, as McGivor said, you do not want to have too high of charging voltage for AGM batteries. They are sealed batteries (VRLA -- Valve regulated lead acid) and if over charged, they will get hot (if they have catalysts in/around each cap) and eventually vent hydrogen+oxygen. Since there is no way to replace lost water, the venting will quickly reduce their overall life.

    Since you cannot (easily) measure SG of a sealed/AGM battery. You will need to pay attention to charging voltage and current (as well as resting voltage and voltage during discharge). They suggest 11.1 volts as the cutoff voltage--You probably want 11.5 volts as your own point to avoid going below with light loads (if you have a heavy load like starting a water pump, etc... A short period of time below 11.5 volts is not going to hurt anything).

    While I tend to harp on not overcharging AGM batteries--The facts are that most AGM (and other battery chemistries) are killed by over discharging/"deficit" charging (where you discharge 100% to 80%, then recharge to 90%, and discharge to 70% and recharge 80%, etc.--Slowly not ever getting back to full charge). With solar, you have limited amount of charging energy (hours of sun in sky, possible bad weather, shading on solar panels, etc.)... Just make sure that the batteries are recharged >90% once or a couple times a week. And avoid going below 50% SoC very often.

    With RV batteries, unless you are living in the vehicle, most of the time, the batteries will "age out" before they "cycle out". I.e., 30 nights a year * 10 years is 300 cycles. Whereas most AGM batteries will last something on the order of 5-7 years in typical solar/cycling (just an average).

    Having 15.0 volts as the charging cutoff voltage is probably not a bad thing for the battery bank... As the battery bank gets cold, the charging voltage is increased. For example, standard temperature is 25C, and say your RV falls to 0C inside (in storage/very cold night):
    • -0.004 volts/C/Cell * 6 cells * (0Cambient-25C) = +0.6 volts
    • 14.4 volts charging (@25C) + 0.6 volts (@0C offset) = 15.0 volts charging @0C
    The battery cutoff voltage would depend on your loads too... AC inverters have their own cutoff voltage of 15.0 to 16.5 volts or so (depending on brand or model)--Other loads (like LED lights, water pump, 12 Volt DC adapters for computers/etc.) will have different cutoff voltages... The ones that tend to be most "picky" (besides AC inverters) are typically 12 volt car adapters (for laptop computers, etc.)... They typically are exposed to ~14.4 volts maximum when used on a car's cigarette lighter outlet... And have been known to be "fried" when connected to a solar battery bank when charging in cold climates.

    For the solar array, the typical "best" output you will see is (note: output charging current depends on solar power in and actual battery voltage) (update for 400 Watt array, not 200 Watt):
    • 200 Watts * 0.77 panel+controller deratings * 1/14.4 volts battery charging) = 10.7 amps (in cool/clear weather, near solar noon).
    • 400 Watts * 0.77 panel+controller deratings * 1/14.4 volts battery charging) = 21.4 amps (in cool/clear weather, near solar noon).
    Note that the battery bank, if not around 80% or less State of Charge, and if you have no other DC loads will naturally limit charging current to less than maximum (typically if you set 14.4 volt Absorb--The battery is limiting charging current to some degree).

    Also, the angle of the solar panel matters too... In northern climates, typically you want to tilt the panel towards the sun. In southern climates, placing the panel flat on roof during summer is less of an issue. You can use a simple solar calculator to estimate the average harvest for your location/season. Say Maastricht Netherlands, fixed flat and 51 degrees from horizontal):
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Maastricht
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a horizontal surface:

    JanFebMarAprMayJun
    0.85
     
    1.50
     
    2.50
     
    3.66
     
    4.83
     
    5.02
     
    JulAugSepOctNovDec
    4.95
     
    4.32
     
    2.92
     
    1.77
     
    0.99
     
    0.66
     

    Maastricht
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 39° angle from Vertical:
    (For best year-round performance)

    JanFebMarAprMayJun
    1.44
     
    2.23
     
    3.02
     
    3.77
     
    4.41
     
    4.35
     
    JulAugSepOctNovDec
    4.38
     
    4.29
     
    3.39
     
    2.50
     
    1.61
     
    1.16
     
    This is March, say flat to roof, your average daily harvest (long term average, some days more, some days less):
    • 200 Watts * 0.61 AGM solar AC power end to end efficiency * 2.5 hours of sun per day = 305 Watt*Hours per day
    • 305 WH per day / 12 volts = 25 Amp*Hours per day @ 12 volts
    In general you want to add as many solar panels to your roof as you can fit (and can $$$). A 400 AH battery bank:

    • 400 AH * 14.4 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 374 Watt array minimum (5% rate of charge)
    • 400 AH * 14.4 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 748 Watt array nominal (full time off grid)
    • 400 AH * 14.4 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 972 Watt array "typical" cost effective maximum
    As you can see your 200 Watt panel is really only enough for "float charging" the battery bank and some light loads. For better battery life, a 5% or 374+ Watt array  would be highly suggested (for weekend RV travels/and or shore power from RV parks, the small array can work if your loads are small).

    If you are looking for many weeks at a time/full time off grid--A 748 Watt or larger array would be a really nice fit.

    And the solar panels should never have ANY SHADE--Even a vent pipe or a tree branch will kill much or all of the solar panel's harvest.

    Questions?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • littleharbor2littleharbor2 Solar Expert Posts: 1,599 ✭✭✭✭
    Some AGM batteries can tolerate higher voltages. This particular one has a charging spec for cycle duty as high as 15.0 volts. Tried to enlarge the photo but don't know how. If readers can enlarge this shot you can see the specs on the left side of the battery.

    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, 540 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • BB.BB. Super Moderators, Administrators Posts: 31,684 admin
    The link for Littleharbor2's battery/photo:

    https://batteryusa.com/wp-content/uploads/2014/03/HRL12540W.pdf

    They talk about 14.4 to 15.0 voltage for cycling... However, only 200-500 cycle life (if 100% or 50% cycled). Not a great life for a solar system (~1,000-1,200 cycles @ 30% discharge).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • DzefaDzefa Registered Users Posts: 18 ✭✭
    edited March 8 #13
    Wow, you guys know a lot about solar power setups :D So much information, difficult to process for such a beginner.

    So @BB.: What do you specifically recommend changing from the below parameters?
    • Batt. type: User
    • Batt. AH: 400AH
    • Temp comp coeff: -3mv/C/2v (unchanged)
    • Rated voltage: Auto
    • Over volt Disc. 16.0V
    • Charge Limit: 15.0V
    • Over volt rec: 15.0V
    • Equal charge: 14.6V
    • Boost Charge: 14.6V
    • Float Charge: 13.8V
    • Boost Rec: 13.2V
    • Low volt Rect: 12.6V
    • Under volt Rect: 12.2V
    • Under Volt warn: 12.0V
    • Low volt Disc: 11.1V
    • Discharge 10.6 V
    • Equalize time: 120 min
    • Boost time: 120 min
    Als I am planning to live full time in the RV. As extra options for power I have a shore connection and the possibility to charge via the engine(alternator). Furthermore, I will mostly be staying in more sunny climates in southern regions of Europe. Do you still think I should upgrade the solar panel array? I estimated my daily usage at 90 A/h. By the way, I have 2x200w (series).

    Maybe one last important piece of info. The 14.9V of the battery was shown at a temperature of around 0 to 5 degrees Celcius.
  • BB.BB. Super Moderators, Administrators Posts: 31,684 admin
    I would still set your charging point to 14.3 or 14.4 for longer battery life.

    Tell us roughly where you will be spending your time (nearest major city)--And can update the harvest estimate... But you can see that at 90 AH a day (note: using your 400 Watt array--I missed the 2x 200 watt panels first time around):
    • 90 AH * 12 volts = 1,080 WH per day
    • 1,020 WH per day * 1/0.61 solar AC system eff * 1/400 Watt array = 4.2 hours of sun per day for "break even" harvest
    That is a relatively large amount of sun with a flat mounted array that you can harvest in most areas of the world outside of "summer"... And if your needs are 90 AH per day EVERY DAY (say for work/refrigerator), you should only plan on using 50% to 65% of your "predicted harvest" for "base loads".

    It would be a good idea for you to measure your charging current from your engine alternator... Say 30 Amps average, your are looking at >3 hours of driving (and realistically 5+ Hours including Absorb time). I would guess that you don't drive that much "daily", and fuel is not cheap in Europe (and getting more expensive in USA now).

    You have the batteries, might need a larger AH rated EPEVER MPPT charger for a much larger array:
    • 30 amps * 14.4 volts charging * 1/0.77 panel deratings = 561 Watt suggested max optimum for 30 Amp MPPT charge controller
    Solar panels are about as cheap as they ever have been... And batteries tend to be about as expensive as they ever have been... More solar panels will help keep your battery bank happier.

    You might also look at the MPPT controller input specifications... Typically they "work better" with a bit higher voltage array:
    • 1.3 fudge factor * 14.4 volt battery bus = 18.7 volts Vmp-array minimum
    • 2 fudge factor * 14.4 volt battery bus = 28.8 volts Vmp-array "nice nominal" Vmp-array voltage
    So placing your 200 Watt panels 2x series connections (as you have) or using larger format (typically >200 Watt) Vmp~30 volt panels are/would be a good fit (large format panels are typically cheaper per Watt vs smaller panels).

    And I did miss that you have 400 Watts of panels in my first reply... So
    This is March, say flat to roof, your average daily harvest (long term average, some days more, some days less):
    • 400 Watts * 0.61 AGM solar AC power end to end efficiency * 2.5 hours of sun per day = 610 Watt*Hours per day
    • 610 WH per day / 12 volts = 51 Amp*Hours per day @ 12 volts

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 31,684 admin
    edited March 8 #15
    I should add... It seems your system is working correctly.. .And 14.9 volts charging @ 0C is certainly to be expected.. If you still have -3mV/C/C:
    • -0.003 volts/C/Cell * 6 cells * (0Cambient-25C) = +0.45 volts
    • 14.4 volts charging (@25C) + 0.45 volts (@0C offset) = 14.85 volts charging @0C
    And if your meter is accurate to 12.xy the "y" digit is going to have some "error"... I would not get overly concerned about a bit of +/- 1 or 2 on the end of the number.
    Longer term, you may want to look at an AC+DC Current Clamp DMM (digital multi meter). Makes debugging (when needed) and understanding your system much easier. I will give amazon . US site... These meters are just suggested starting points for your search:
    https://www.amazon.com/gp/product/B00O1Q2HOQ (inexpensive, good enough for our debugging needs)
    Note, there are also AC only clamp meters--They are very nice, but don't work on the DC side of our systems. They will have an AC+DC DMM (voltmeter) function too--But that is not the AC+DC current clamp function.
    I am not saying that my "answers" are the only answers or even the correct answers for you. The math (and derating/efficiency fudge factors) are there to get quickly to answers that should "bracket" your needs.
    And, obviously, I do make mistakes (If nothing else I am consistently wrong :s).
    Please feel free to ask more questions... We try to show our work and how we got there/here. That way, you can do your own math with different needs/assumptions and see how that affects your choices.
    In general, solar is easily 2-10x more expensive that utility power (when everything is taken into account--panel, electronics, batteries+replacement batteries, repairs)...
    So step #1 is usually to look at your loads and find the most efficient loads you can (LED lighting, small laptop computer vs full size desktop computer, etc.) can save you money over time... It is almost always cheaper to conserve energy than to generate energy.
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Solar Expert Posts: 3,815 ✭✭✭✭✭✭
    Something I hadn't considered was cold temperature raising the voltage, therefore using 15V as Bill pointed out is probably fine, my circumstances are the opposite, mostly above 25°C and the reason I suggested waiting for others to contribute.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • BB.BB. Super Moderators, Administrators Posts: 31,684 admin
    Do note that most all solar charge controllers have a temperature sensor inside the controller... And some support a remote temperature sensor. So in this case--The temperature is the room temperature where the controller is mounted.

    The ideal installation is to have the solar charge controller in the same room/temperature that the battery bank. For (typically) higher end controllers--They have an RBTS (remote battery temperature sensor--option) and you mount the sensor to the battery bank, and can install the controller elsewhere.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • DzefaDzefa Registered Users Posts: 18 ✭✭
    edited March 9 #18
    Thanks Bill & McGivor!

    "I would still set your charging point to 14.3 or 14.4 for longer battery life."

    So you recommend I change "Boost Charge" from 14.6V to 14.3/14.4? All the other parameters I can keep the same?

    "And if your needs are 90 AH per day EVERY DAY (say for work/refrigerator), you should only plan on using 50% to 65% of your "predicted harvest" for "base loads".

    This 90AH is not every day, this is kind of the maximum I can expect on one day. This would be in the case that im working for example a whole day from my laptop. For consistent energy needs I only have a 12v fridge running (Indel B 130L) at about 36 Ah per 24 hours. All the other devices (Fan 12v, inverter, diesel heater, water pump, power plugs, led lights) I can minimize in usage.

    "You have the batteries, might need a larger AH rated EPEVER MPPT charger for a much larger array:
    • 30 amps * 14.4 volts charging * 1/0.77 panel deratings = 561 Watt suggested max optimum for 30 Amp MPPT charge controller
    Solar panels are about as cheap as they ever have been... And batteries tend to be about as expensive as they ever have been... More solar panels will help keep your battery bank happier."

    I would be very cheap and quite easy for me to get one more solar panel installed. I have place for one extra 200W panel, which would total to 600W. Reason why I am doubting is exactly what you describe. I would have to replace my brand new MPPT even before I have used it :D What I am thinking of now is to try it for a while on my current 400w (in combo with the alternator and the shore power smart charger). If after a month or two I find out that it is not working properly, I upgrade to an extra 200W and an upgraded MPPT. Good idea? Also what size of MPPT would I need in that case, 40A?

    "Do note that most all solar charge controllers have a temperature sensor inside the controller... And some support a remote temperature sensor. So in this case--The temperature is the room temperature where the controller is mounted."

    This MPPT has a temperature sensor inside. I have the MPPT mounted in the same area and only a few centimeters from the batteries. The temperature should be the same.

    "Tell us roughly where you will be spending your time (nearest major city)--And can update the harvest estimate."

    Kind of all over the place :D But to give a rough estimate:
    • April - May : Antalya, Turkey
    • June: Podgorica, Montenegro
    • July - August: Trondheim, Norway
    • September: Amsterdam, Netherlands
    • October - November: Lisbon, Portugal
    • December - March: Santa Cruz de Tenerife, Canaric Islands Spain
    "I should add... It seems your system is working correctly.."

    So how can I test this to know this for sure? What I did yesterday/doing this morning:
    • Turned off the solar input (charging off)
    • Turned on many devices to attempt to discharge the batteries
    • This morning early turned off the devices
    • Batteries are giving 12.88V, based on which I assume that they are at around 90% capacity. I was hoping that the batteries would be at around 60-70%, but didnt achieve that.
    • Now I will turn on the solar panels in full sun and hope to see some higher Amp numbers showing up. 
    • Is this a good test?
    Just finished the test, the results:

    PV                           Battery                    Load
    40.5V                        13.4V                     0.0V
    4.6A                          13.8A                     0.0A

    So this seems to me that the setup is working properly, right? This was right after turning the solar panels on again, early morning sun (10.30 AM) (slight cloud) and at about 5 - 8 degrees celcius.

    Thanks a lot guys! Besides this info being very helpful it is also very interesting and fun to learn!

    -Jeff


  • mcgivormcgivor Solar Expert Posts: 3,815 ✭✭✭✭✭✭
    edited March 9 #19
    "I would be very cheap and quite easy for me to get one more solar panel installed. I have place for one extra 200W panel, which would total to 600W. Reason why I am doubting is exactly what you describe. I would have to replace my brand new MPPT even before I have used it"D
    As an alternative to replacing the charge controller you could add a second and program identical settings.


    "I should add... It seems your system is working correctly.."

    So how can I test this to know this for sure? What I did yesterday/doing this morning:
    • Turned off the solar input (charging off)
    • Turned on many devices to attempt to discharge the batteries
    • This morning early turned off the devices
    • Batteries are giving 12.88V, based on which I assume that they are at around 90% capacity. I was hoping that the batteries would be at around 60-70%, but didnt achieve that.
    • Now I will turn on the solar panels in full sun and hope to see some higher Amp numbers showing up. 
    • Is this a good test?
    Discharge the batteries a little deeper to get a better idea of what they will produce in your current location, I would suggest down to around 12.3V, they will recover slightly, the amount would be dependent on load size used to discharge. Getting critical  information before using the system will help understand the limitations.



    So you recommend I change "Boost Charge" from 14.6V to 14.3/14.4? All the other parameters I can keep the same?

    Perhaps 14.4V would be a starting point, the lowest default algorithm my Morningstar controller (a world leader in solar charge controllers) has for sealed batteries is 14.35V. Perhaps a low equalization setting of  14.6V -14.8V could work as a monthly cell alignment charge. The definition of cycle may mean completely discharged as in a standby application, the recommendation for storage charging every 6 months is 14.4V to 14.7V,  to get a definitive answer contact the manufacturer giving them details on depth of discharge etcetera, every application is different hence the broad recomendations.





    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, 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: 1,599 ✭✭✭✭
    On the positive side of the coin, if you don't discharge those batteries much more than 25% , and not used in a full time set up you should get around 5 years, maybe more, out of them. I have seen people ruin flooded batteries in a couple years with poor, or no maintenance.

    I have a set of them running my place now, full time. Bulk voltage set to 14.9. 18 months on the clock so far. I'll report back in the event of an early death.  :#

    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, 540 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

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