Victron MPPT Controllers

bigbillsd
bigbillsd Registered Users Posts: 28 ✭✭
in Caravan, Recreational Vehicle, and Marine Power Systems #1
Hi again,  I have a quandry I am trying to find a work around.   I realize my controller cannot completely charge my batteries on the Sun due to the way the charge controller limits the power to the batteries in Absorb then Float.   So I am running the genny for an hour in the morning to bulk up the battery to about 80% or so.  Then the controller runs in bulk for an hour or two and then absorb for a short period of time due to the battery voltage being a bit higher when it wakes up during the genny charging.  So it goes into Float way too soon. 

I am normally running the Inverter all day and night and quite often the Controller in Float produces less than what the inverter is using so I am negitivly charging about an amp or so.   How do I fool the controller to put out more amperage to at least be putting in the 4-5 amps into the battery it thinks its putting in but is not due to load on the batteries?   Ideas?  -Bill  
4 each Renogy 160w Solar Panels mounted flat on RV roof, Serially connected @ ~80v,  Victron 100/50 MPPT controller.  520AH LA batteries @ 12volt, 2800w PSW Magnum Inverter.   Bogart Trimetric. 
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,626 admin
    #2
    What is the battery terminal voltage (the charge controller's output terminals should be within 0.05 to 0.10 volts of the 12 volt battery terminal voltage).

    If the controller is working correctly... It is should hold the setpoint voltage (up to ~100% of the avialable current from the solar array).

    If the battery bus voltage is sagging when under load, check the terminal voltages on the charge controller (both Vpanel in and Vbatt out) and let us know what they are, and the current.

    You can put your system configuration in your signature line, and we don't have to keep asking what brand/model/type of charge controller, battery bank AH and voltage, solar array size/configuration. (link should work for everyone):

    https://forum.solar-electric.com/profile/signature/

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,907 ✭✭✭✭✭✭
    #3
    Yes please help with some data. The manual should show how to limit charge current? If this is new equipment it should be at max current.
    If someone else owned it, maybe they have limited the current.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • bigbillsd
    bigbillsd Registered Users Posts: 28 ✭✭
    edited October 2018 #4
    My current CC settings are 14.5v Absorb,  13.5v Float.   Its a new controller.  I am not trying to limit it, I know the panels can produce a lot more at the time I show it going into float.   You may need to dumb down your questions. 
    Solar Voltage 76.39v
    Solar Current 0.9a
    Batt Voltage 13.37
    Batt Current 5.1a

    Inverter load and other parasitic loads are 6.3a  Trimetric showing  -1.2a (discharging battery at 1.2a)

    I know there is a lot of power that can be produced at that time.  If I disconnect the CC it will go into Bulk charging and start putting in 17a or more.  So I don't understand why the CC isnt producing enough current to power the inverter load and still add a few amps into the battery too.

    -Bill

    PS.  Config added to signature.
    4 each Renogy 160w Solar Panels mounted flat on RV roof, Serially connected @ ~80v,  Victron 100/50 MPPT controller.  520AH LA batteries @ 12volt, 2800w PSW Magnum Inverter.   Bogart Trimetric. 
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited October 2018 #5
    There is no reason to try fool the controller into doing anything, baring any current limitations, the controller itself is controlled by the battery voltage, whatever the settings are, it should follow those settings, if the battery is fully charged and has transitioned into float the current would be reduced to a small amount to prevent self discharge. Whilst in float, if load were introduced, be it via an inverter or a DC load, the PV should provide the current, if available, via the controller to support the load, if there is any deficit the battery will be called into duty to make up the deficit. 

    To evaluate what is happening use the method  as follows, power down everything, starting with the inverter, then PV to the controller, then battery, wait a few minutes connect battery to the controller, allow time to reboot, then connect PV, allow it to fully charge the battery, once in float apply a load, the inverter in your case, current from the controller should increase as it's diverted to the load, as long as the load doesn't exceed the PV's ability to support it, the battery voltage should remain constant and no current should be withdrawn from the bank. This is a systematic approach, sometimes trying to evaluate a perceived fault can be masked in the dynamics of a system, so breaking it down into fundementals is often the better approach.      
    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.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #6
    Maybe a bit of a long shot, but...
    Do you have a remote temp/voltage sensor?  Assuming not, I wonder if the internal sensor in the controller is getting warm and fooling the controller into compensating the voltage down?  Eventually voltage would drop to the compensated value, but in the meantime there would be a negative amp value showing on the TM.
    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
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #7
    If it's going into float the charge controller believes the battery is fully charged.

    bigbillsd said:
    Inverter load and other parasitic loads are 6.3a  
    This 'parasitic load, is about all you can expect your system to produce in a day, and is more that it may be able to average depending on your insolation. If you averaged 4 hours of direct sun per day, you system is likely to produce 640 watt array x 4 hours = 2560 watt hours, panels typically produce 75% of their name plate 2560 x .75 = 1920 watt hours.

    6.3 amp load at 13.37 volts is 84 watts per hour. 84 x 24 hours = 2016 watt hours.
    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.
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  • bigbillsd
    bigbillsd Registered Users Posts: 28 ✭✭
    #8
    Estragon said:
    Do you have a remote temp/voltage sensor? 
    I have a remote battery sensor on order now.  We are not dry camping again till a week at Quartzite in January.  -Bill
    4 each Renogy 160w Solar Panels mounted flat on RV roof, Serially connected @ ~80v,  Victron 100/50 MPPT controller.  520AH LA batteries @ 12volt, 2800w PSW Magnum Inverter.   Bogart Trimetric. 
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  • bigbillsd
    bigbillsd Registered Users Posts: 28 ✭✭
    #9
    I just installed the smart battery sense device and linked it up with the controller via Bluetooth.   If I leave the controller bay door and the battery bay door open all is good,  i see the temperature of the batteries on the controller screen.  If I close either bay door.  (the sensor is 6' from the controller) the temperature goes away.. I assume that means they are no longer talking.   I don't see a wired sensor, I guess I need to keep looking.  I'm starting to wonder if this Victron stuff is a bit too "rinky dink" and need to look at other options.   
    4 each Renogy 160w Solar Panels mounted flat on RV roof, Serially connected @ ~80v,  Victron 100/50 MPPT controller.  520AH LA batteries @ 12volt, 2800w PSW Magnum Inverter.   Bogart Trimetric. 
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,626 admin
    #10
    Flooded Cell Lead Acid batteries or AGM?

    If flooded cell, bump the charging voltage to 14.8 volts and float to 13.8 volts and watch the electrolyte levels... If you are adding a lot of water every 1 month or less, back down on charging set points a bit.

    If you have to add water every 6 months or longer between fills, then you are probably not charging at high enough voltage/long enough time (in Absorb).

    When the solar charge controller is outputting a lot of current--Measure the battery bus voltage and the controller Vbatt terminal voltage. Ideally, you want around 0.05 to 0.10 voltage drop maximum from charge controller terminals to battery bank terminals.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • bigbillsd
    bigbillsd Registered Users Posts: 28 ✭✭
    #11
    I am using LA batteries.  See my signature.    And since I installed the Smart Battery Sense the controller is staying in absorb for 2 hours each day after a small discharge.   We are heading out for a week of dry camping so it will be interesting to see if it will stay in absorb for most of the day after a 150 AH discharge.   -Bill
    4 each Renogy 160w Solar Panels mounted flat on RV roof, Serially connected @ ~80v,  Victron 100/50 MPPT controller.  520AH LA batteries @ 12volt, 2800w PSW Magnum Inverter.   Bogart Trimetric. 
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,626 admin
    #12
    What voltage are you seeing during absorb (at the battery bank terminals)?

    And Flooded Cell and AGM batteries are both Lead Acid type batteries. Flooded cell you can pop the cap off and check electrolyte levels and specific gravity (with a hydrometer). AGMs are sealed and best you can do is monitor the charging/discharging/resting voltages and currents.

    14.5 volts absorb can be a bit on the "high side" for AGM (sealed) batteries (typically they use 14.4 volts maximum). And for FLA type batteries ~14.75 volts is a typical starting point for Absorb voltage.

    With a temperature sensor, the actual voltage will be adjusted by (-0.005 mVolts*#cells*(25C - actual battery temperature)... Or (-0.005 * 6 cells for 12v batt * delta of 10C) = -0.3 volts per 10C .... If 5C, charging voltage will be +0.3 volts over set point... If 35C, charging voltage will be -0.3 volts below set point.

    A 2,800 Watt @ 12 volt AC inverter on a 520 AH @ 12 volt battery bank is pretty large... AGM type batteries can support more surge current than FLA batteries... Typically, the "reliable" maximum AC inverter (and maximum solar array) I would suggest would be:
    • 520 AH * 250 Watts/100 AH capacity = 1,300 Watt AC inverter (and max "cost effective" solar array) suggested
    Realistically, due to wiring and voltage drop, a maximum recommended AC inverter would be ~1,200 to 1,800 Watts for any "typical" 12 volt system... You have to have a pretty heavy and short set of battery cables to AC inverter to manage 2,800 Watts continuous load:
    • 2,800 Watts * 1/0.85 AC inverter eff * 1/10.5 volts inverter cutoff voltage = 314 Amps @ 12 volts
    • 314 Amps * 1.25 suggested derating for wiring and fuse/breaker = 392.5 rated branch circuit (wiring and fuses)
    Another issue is that your inverter draws ~30 Watts (30w/12v=) or 2.5 Amps @ 12 volts... That is a pretty significant load for an RV system... If left on 24 hours, you are looking at (24h*2.5a=) 60 AH of your planned 150 AH per day loading. Almost 1/2 of your energy usage....

    You have to be careful and only run the inverter when you need the power... You can also get a ~300 Watt AC inverter that will run about 6 Watts (Tare--No power "just turned on") to run your smaller stuff (LED lighting, laptop, cell charge, etc.) when you do not need the larger inverter.

    https://www.solar-electric.com/lib/wind-sun/Magnum-MS-Inverters.pdf

    I guess you have a generator for backup/charging your battery bank?

    Your 160 Watt array could produce (on average) (say you are camping somewhere near):
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    San Bernardino
    Average Solar Insolation figures

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

    JanFebMarAprMayJun
    2.99
         		3.73
         		5.28
         		6.60
         		7.34
         		7.64
     
    JulAugSepOctNovDec
    7.22
         		6.62
         		5.58
         		4.40
         		3.34
         		2.79
     

    Or:
    • 4 panels * 160 Watt array * 0.52 average off grid AC system eff * 2.99 hours (average January) sun per day = 1,167 WH per day of AC per day (Jan)
    • 4 * 160 Watt array * 0.61 ave DC OG system eff *  1/12 volt system * 2.99 Hours = 97 AH @ 12 volts per day
    Anyway, some basic math to play with depending on where you camp and how many hours per day you run the AC inverter...

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