2 55 watt solar kits

vidaliamanvidaliaman Registered Users Posts: 12 ✭✭
can i have one 55 watt kit controller charging one 12v battery and the other 55 watt kit  controller charging the other 12v battery hooked together in sequence(pos to pos, neg to neg) and one 400 inverter hooked to the pos of one battery and the neg to the other battery? will the two controllers clash in some way?
thanks dave

Comments

  • PhotowhitPhotowhit Solar Expert Posts: 5,650 ✭✭✭✭✭
    If you have 2 batteries connected pos to pos and neg to neg, you have 1 battery bank! We call this connected in parallel.

    Typically there is no problem hooking up more than 1 charge controller to a battery bank. If the batteries are different sizes, there will be capacity issues. The charge controllers won't be exactly in the same calibration, so they will change modes at different times.
    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.
  • vidaliamanvidaliaman Registered Users Posts: 12 ✭✭
    thanks for the info, so with 2 equal batteries is it better to hook one controller to one battery and the other to the other battery(connected in parallel)? or is it better to hook both charge controllers to the neg of one battery and the pos of the other battery? thanks again, learning alot
  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited May 2017 #4
    If you connect 2 batteries in parallel you have essentially created one battery, the charge controllers output would be combined, in parallel , connected diagonally opposite on the positive and negative terminals. Like the last statement, or is it better to hook both charge controllers to the neg of one battery and the pos of the other battery? 
    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: 32,005 admin
    About connecting batteries in parallel (as well as loads and charge controllers):

    http://www.smartgauge.co.uk/batt_con.html

    Short answer is yes, you can parallel several charge controller to one battery bank (connected as in link above).

    Also, it is a good idea to use a circuit breaker/fuse(s) to protect the wiring leaving a battery bank. A typical size lead acid battery bank can output hundreds to thousands of Amperes into a dead short. For each positive wire that leaves the battery bank, a fuse/breaker should be used to protect that wire (i.e., 14 AWG wire, use a ~15 amp breaker/fuse). These over-current protection devices are there to prevent the wiring from overheating and causing a fire if there is a short circuit in the down stream wiring or attached loads.

    A pair of car batteries setup for 24 volts makes a very nice emergency arc welder too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vidaliamanvidaliaman Registered Users Posts: 12 ✭✭
    15 amp breaker between the battery bank and the inverter correct?
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    The inverter documentation should call out the wiring and breaker/fuse needed--But generically:
    • 400 watt inverter * 1/0.85 inverter eff * 1/10.5 volt battery cutoff = 44.8 amps max continuous
    • 44.8 amps * 1.25 NEC and branch circuit wiring derating = 56 Amp rated wiring+breaker/fuse minimum
    The above will reliably supply 400 Watts of 120 VAC power... And support 2x 12 VDC current flow for a few seconds for surge current (starting a motor, etc.).

    Of course, the maximum current/surge current from your battery bank depends on the size of the battery bank. Using our rule of thumb of 100 AH @ 12 VDC per 250 Watt of AC inverter rating:
    • 400 Watt inverter / 250 Watts per 100 AH @ 12 volts = 160 AH @ 12 volt minimum flooded cell lead acid battery bank
    I.e., a pair of "motorcycle" batteries in parallel will not supply enough current to run a 400 watt AC inverter at rated output power.

    And, incidentally, in general the same equation applies to the maximum recommended solar array of ~400 watts for a 160 AH @ 12 volt battery bank.

    The above is a very rough (conservative) answer to what could be a very complex set of questions (what are your power needs, emergency backup, daily cycling, quality/specifications of hardware, specific battery type flooded cell lead acid/AGM/etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vidaliamanvidaliaman Registered Users Posts: 12 ✭✭
    that is good info, here is what i have...   2 sets of coleman 55 watt kits, each comes with it's own controller(7amp), my needs are only in the evenings tv/dish and a handful of led lights 3 or 4, i am looking at 2 identical 12v batteries in parallel, would i connect each controller to each battery(batteries that are connected parallel) or would i connect both controllers to the 2 battery bank?   i have been taking a charged 12v battery to my cabin, in the evenings we watch tv, i have a 400watt inverter that my tv and dish equipment run off of and this will last the weekend, i bring my battery back pop it on a trickle charger and it's ready the next time i go north, it is also nice to be able to flip on a led light at night to goto the bathroom. any other recommendations anyone would have for this equipment would be awesome, i will soon go full tilt into solar and move the 2 small kits to my barn to keep tractor batteries charged.
    thanks dave
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    Can you tell us more about your batteries (agm, flooded cell, amp×hour rating).

    Near what major city will the system be used?

    Weekend, summers, 12 months a year usage?

    Generally, you connect the charge controllers and battery bank to the same bus bars/connections.

    - Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vidaliamanvidaliaman Registered Users Posts: 12 ✭✭
    great question, have not bought them yet, what do you recommend? closest city:newberry michigan, weekends 7 months a year
  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    If you haven't bought the batteries then consider buying a single larger capacity one to do away with parallel connections.
    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: 32,005 admin
    A pair of 55 Watt panels can nicely drive a battery bank size of (at 5% to 13% rate of charge):
    • 110 Watts * 1/14.5 volts charging * 0.77 panel+controller derating * 1/0.05 rate of charge = 121 AH @ 12 volt battery maximum (weekend/seasonal usage)
    • 110 Watts * 1/14.5 volts charging * 0.77 panel+controller derating * 1/0.10 rate of charge = 60.5 AH @ 12 volt nominal (full time off grid)
    • 110 Watts * 1/14.5 volts charging * 0.77 panel+controller derating * 1/0.13 rate of charge = 47 AH @ 12 volt minimum "cost effective" battery
    Using PV Watts, fixed array at 45 degrees for SAULT STE. MARIE, MI:
    http://pvwatts.nrel.gov/pvwatts.php
    MonthSolar Radiation
    ( kWh / m2 / day )
    January2.70
    February3.88
    March5.20
    April4.97
    May5.59
    June5.54
    July5.49
    August5.29
    September4.16
    October3.26
    November2.27
    December2.17
    Annual4.21
    Say use the system March through September, the minimum sun is around 4.16 Hours per day (long term average):
    • 110 Watts * 0.52 off grid system eff with AC inverter * 4.16 hours of sun (September) = 238 WH per day solar
    A 121 AH @ 12 volt battery has enough storage of 2 days (weekend of no-sun) and 50% max discharge (longer battery life):
    • 121 AH * 12 volts * 0.85 AC inverter eff * 1/2 days storage * 0.50 max discharge = 309 Watt*Hours per day nominal storage
    -Bill



    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    I would recommend flooded batteries.  They're generally cheaper than AGM, and the ability to check specific gravity and add water is a big advantage, especially for someone new to solar and off-grid.  AGM also tend to have different charging requirements than flooded, and you would need to compare the charging regime the kit provides to the battery makers recommendations.

    The main advantage to AGM in your application is they generally have lower self-discharge than flooded, which could be an advantage if you want to leave the battery at the cabin over the winter with no charging source.  Flooded batteries will self-discharge much more slowly when cold, and won't freeze if left fully charged.
    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
  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    The small 55 W chargers are probably not designed for a flooded battery,, probably pwm with a fixed algorithm and better suited to a sealed lead acid, such as an AGM, but without specific details, I could be wrong.
    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.
  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    @mcivor is correct, if the manual I checked is the right one. It says the battery is charged at 14.2v, which is low for flooded unless the battery is really warm.
    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
  • vidaliamanvidaliaman Registered Users Posts: 12 ✭✭
    if i were to buy a single larger capacity battery can i hook both controllers to a single battery?
    this is great info, thanks all
  • vidaliamanvidaliaman Registered Users Posts: 12 ✭✭
    also when you are talking about larger capacity what would be a good capacity example?  and where would this large capacity be available? thanks
  • vidaliamanvidaliaman Registered Users Posts: 12 ✭✭
    here are my controllers... one 7 amp controller for each of my 2 55w panel arrays, it says i can use just one controller for 105 watts of solar power, if i had just one battery with large capacity what would be recommended?
    cut in voltage - 13 volts
    cut out voltage - 14.2 volts
    max load 105 watts/7 amps

  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    You really want to design the system to support your needs... For example, here are a few points that are good starting places (to figure out designs and costs if you do not know your loads yet):
    • 1,000 WH per day (30 kWH per month)-- Run LED lighting, laptop computer, RV type water pump, cell phone charger
    • 3,300 WH per day (100 kWH per month) -- Add a refrigerator, well pump, clothes washing machine, LED TV (very efficient cabin/home, family--Near normal electrical life -- perhaps optional A/C or heat pump for hot summer days)
    • 10,000 WH per day (300 kWH per month) -- A reasonably efficient urban home -- Toaster oven, microwave, electric coffee maker, washer/drier, central heating (natural gas, propane, etc.).
    • 33,000 WH per day (1,000 kWH per month) -- Typical home with A/C, no conservation, electric heat/hot water/drier
    • 100,000 WH per day (3,000 kWH per month) -- Heavy A/C usage in central Texas
    A 1,000 WH per day is very nice for a cabin. Use a genset for heavy loads (running tool, washing machine, pump to cistern when needed). A system like that could look like:
    • 1,000 WH per day * 1/0.85 AC inverter * 1/12 volts * 2 days storage * 1/0.50 max discharge (longer battery life) = 392 AH battery bank @ 12 volts
    That would be 2x 6 volt @ 200 AH "golf cart" batteries in series with 2x parallel strings (4 batteries total) for a 12 volt @ 400 AH battery battery bank. Note there are lots of battery sizes and AH ratings. Golf cart batteries are generally cheap and easy to get. If you mess up, you have not blown a lot of money (yet). You also can get 2 volt cells @ >1,000 AH (put 6 in series for a 12 volt @ 1,000 AH+). Do not get too wrapped up in the details until you have a system on paper (and I suggest to not buy any hardware until you have a workable paper design plus parts list). For more battery options, here is a link to our host (batteries, you may end up buying them locally to save on shipping costs). Trojan (link below) is a nice middle of the road vendor (there are lots of options out there--Just giving you a starting point to start your research):

    https://www.solar-electric.com/residential/batteries-battery-storage/deep-cycle-batteries.html?manufacturer=Trojan+Battery&p=2

    Install a nice smaller 300 Watt TSW AC inverter like this Morningstar 12 VDC unit for AC power.

    Solar array size--Two calculations. first based on battery bank size (larger battery bank needs larger solar array for proper charging current):
    • 400 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 377 Watt array minimum (weekend/seasonal/emergency backup power/playing around with solar usage)
    • 400 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 753 Watt array nominal (full time off grid usage)
    • 400 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 979 Watt array "cost effective" maximum
    And then there is sizing based on your loads... Let me guess this is a summer cabin, minimum generator use (or no generator) with 4 hours of sun per day minimum:
    • 1,000 WH per day * 1/0.52 off grid AC system losses * 1/4 hours of sun "break even day" = 481 Watt minimum array based on loads
    Say you (and family+friends) use the cabin heavily during the good weather (weeks to months at a time), and you do not want to watch your system+loads like a hawk. Use 10% rate of charge and 753 Watt array. That will give you an estimated minimum amount of energy of:
    • 753 Watt array * 0.52 system eff * 4.0 hours of sun (late September) = 1,566 WH per day
    Assume 1,000 WH of energy usage over night (and/or a couple dark/stormy days of no sun). The "balance of the power used during the day (running a laptop, some video games, cell phone charging, water pump for showers, etc.).

    The above is a "rule of thumb" designed system that will meet the specifications that I laid out above, reliably. If you have specific needs that are not "generic" off grid cabin loads--We need to specify those and, perhaps, tweak the system design a bit.

    Now--Only you can tell us if that size of system will fit your needs.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    You can hook both controllers to a single battery.

    As Bill said earlier, your panels will support ~100-120ah of battery for weekend use.

    Get AGM (deep cycle, not automotive starting type) battery as voltage is low for flooded.
    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
  • vidaliamanvidaliaman Registered Users Posts: 12 ✭✭
    i'll be printing the above info, awesome!!! just learning, just an overview of what i want to accomplish for this year...
    3 season cabin in the upper peninsula of michigan, no tree interference, total sun light(when sunny), starting with 2 55 w panel kits, what i'm trying to accomplish this year is evening and morning dish/tv(winegard satellite)  and at most a half a dozen led lights, we run an e2000 honda genny at times during day when needed, just don't want to hear a genny at night when watching tv or getting up in the middle of the night nto light up the bathroom, i will soon up grade and move my 2 55 watt solar kits 100 yards away to my barn for lights 
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    So, working backwards, a reasonable 110 Watt solar panel will output AC power of:
    • 110 Watt * 4.0 hours of sun per day (early spring/late fall) * 0.52 AC system eff = 229 Watt*Hours per day
    If your stat system is ~25 volts and your TV ~60 Watts (larger LED TV), or 85 Watt total:
    • 229 WH per day / 85 Watts = 2.7 hours of big screen TV per day
    The MorningStar inverter I suggested has both a "sleep mode" (only turns on with >~6 Watts of load) and a remote on off (12 volt signal wire--Just connect to a simply on/off switch or mechanical timer for when you want AC power). Inverters draw power when on and no loads (the MorningStar around 6 Watts when "on", larger inverters can draw 10-40+ Watts) which can be significant if the inverter is running 24 hours per day but only loaded 3 hours per day.

    Get a Kill-a-Watt type meter and measure the energy usage of your proposed devices. Many times, it is the smaller loads running 10-24 hours per day day that are "harder" on a system than running a microwave oven for 10 minutes per day (although, the system also has to be large enough to supply 1,500-2,000 watts for 10 minutes too).

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