What do I want?

oil pan 4oil pan 4 ✭✭✭✭Solar Expert Posts: 766 ✭✭✭✭
I would like to finely build a small/cheap off grid set up I have been thinking about putting together. I just need to find a charge controller that can run 3 power sources to charge a big deep cycle AGM battery, it would need to handle up to 10 amps of solar, up to 30 amps from a generator (I can reduce this if needed) and would like a 3rd option to hook up a wind turbine like the one in my sigature (rated for 500w but never put out more than 200w).
This would be an inverter-less all DC setup with lights, LEDs, fans, motors, pumps and so on.

Can I buy one charge controller to do it all or do I need 3 different ones?

Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

Comments

  • CariboocootCariboocoot ✭✭ Banned Posts: 17,615 ✭✭
    Re: What do I want?

    As far as I know there is not one charge controller made that can handle three different inputs.
    Solar, wind, and generators all have quite different output characteristics. That makes it very difficult to construct a single unit that can handle all three simultaneously.

    Your specs are a bit unusual. If you want 10 Amps peak power from solar then you're charging about 100 Amp hours of battery. That same battery isn't going to like taking 30 Amps (same Voltage) from a generator. Usually a generator's capacity would be pretty much the same as the panels', plus a bit more for taking the loads while the batteries charge.

    Do you have Watt hour and Voltage figures for the DC?
  • nielniel ✭✭✭✭ Solar Expert Posts: 10,311 ✭✭✭✭
    Re: What do I want?

    solar will need a cc, wind will need its own cc and usually has one with it, generators need a 3 stage charger to be plugged into it and not a controller.
  • oil pan 4oil pan 4 ✭✭✭✭ Solar Expert Posts: 766 ✭✭✭✭
    Re: What do I want?

    I know wind and think its usually more trouble than its worth. So forget about that part.

    The battery would be fairly small, the one I have in mind is 44ah. It would be a 12v system.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • BB.BB. admin Super Moderators, Administrators Posts: 29,634 admin
    Re: What do I want?

    Based on battery size and 5% to 13% rate of charge:
    • 44 AH * 14.5 volts * 1/0.77 derating * 0.05 rate of charge = 41.4 watt minimum panel
    • 44 AH * 14.5 volts * 1/0.77 derating * 0.10 rate of charge = 82.8 watt "nominal" panel
    • 44 AH * 14.5 volts * 1/0.77 derating * 0.13 rate of charge = 108 watt "rough maximum cost effective" panel

    How much energy--Assume 4 hours of sun minimum per day (5 hours in summer--probably less in winter):
    • 41.4 watts * 0.52 system derating * 4 hours of sun = 86 WH per day (assuming AC inverter)
    • 82.8 watts * 0.52 system derating * 4 hours of sun = 172 WH per day (assuming AC inverter)
    • 108 watts * 0.52 system derating * 4 hours of sun = 224 WH per day (assuming AC inverter)

    If you want just DC power out of the system--Do the above and assume 0.61 derating and 1/12 volts for AH output. Example:
    • 82.8 watts * 0.61 system derating * 4 hours of sun * 1/12 volts = 16.8 AH per day (assuming DC only)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oil pan 4oil pan 4 ✭✭✭✭ Solar Expert Posts: 766 ✭✭✭✭
    Re: What do I want?

    Thanks bill.
    Like I thought the 44ah will provide plenty of power, its only going to be used a few times a week or on the weekend.
    I never really followed off grid systems. I take it the slightly higher derate factor for DC is because its a little more efficient to not have an inverter going?

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • BB.BB. admin Super Moderators, Administrators Posts: 29,634 admin
    Re: What do I want?

    A quick look at derating rules of thumbs (again, I choose worst case of nominal--I.e., warm dusty panels, capture power during the day and use at night--so battery efficiency matters, etc.).

    Also, some items, like battery efficiency are highly variable... you can run an AGM bank at ~98% efficiency or a flooded cell at less than 80% if you are shallow cycling. But it usually is "close enough" for design work here... And things like inefficient shallow cycling may become more efficient deep cycling during heavy usage.

    In Winter, MPPT charge controllers/GT inverters collect more energy from higher solar panel Vmp-array--Get a bit more power in winter. So things get a bit better rather than worse.

    On the other hand, older batteries and dirty panels are less efficient--So designing for best efficiency when new and then struggling a few years down the road with 10-20% less available power as things age--is not great either:

    • Solar Panel derating: 81%
    • Solar Charging: 95%
    • Solar Panel * Solar Charger derating: 0.81*0.95=0.77=77% efficiency
    • AGM Battery: 90%
    • Flooded Cell Battery: 80%
    • Inverter Eff: 85%
    • AC charger Eff: 80% (typical).

    So, looking at a DC output system (no AC inverter):
    • 0.77 panel+charger * 0.80 flooded cell = 0.616 derating for flooded cell
    • 0.77 panel+charger * 0.90 AGM = 0.693 derating for AGM
    • 0.77 panel+GT Inverter = 0.77 Grid Tied system
    • 0.77 panel+charger * 0.80 flooded cell * 0.85 AC Inverter Eff = 0.5236 w/ AC Inverter

    Make sense?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oil pan 4oil pan 4 ✭✭✭✭ Solar Expert Posts: 766 ✭✭✭✭
    Re: What do I want?

    Ok I see, compounding inefficiencys.
    I can see the dirty panels, lucky for me these are about chest high, and in NM they will get dusty.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • WaterWheelWaterWheel ✭✭✭ Registered Users Posts: 328 ✭✭✭
    Thanks for pointing this old thread out to me BB.      Understanding the calculating of inefficiencies is important as I chose my charge controller and this is a thread well worth reading.

    My inverters (both the PT-100 and soon to be Conext 80-600 ) claim 98% typical efficiency.       The SW-285 panels are ground mount in an area that gets plenty of rain so they stay fairly clean and I'd suspect they will be a little higher than your 82.8% efficient "normal panel" so for my system I suspect I'll end up closer to 88%  efficiency fairly often.      When choosing a charge controller this is the number I need to determine if the Conext 80-600 is capable of handling the load. 

    Conext XW6848 with PDP, SCP, 80/600 controller, 60/150 controller and Conext battery monitor

    21 SW280 panels on Schletter ground mount

    48v Rolls 6CS 27P

  • PhotowhitPhotowhit ✭✭✭✭ Solar Expert Posts: 5,007 ✭✭✭✭
    foolami said:
    Thanks for pointing this old thread out to me BB.      Understanding the calculating of inefficiencies is important as I chose my charge controller and this is a thread well worth reading.

    My inverters (both the PT-100 and soon to be Conext 80-600 ) claim 98% typical efficiency.       The SW-285 panels are ground mount in an area that gets plenty of rain so they stay fairly clean and I'd suspect they will be a little higher than your 82.8% efficient "normal panel" so for my system I suspect I'll end up closer to 88%  efficiency fairly often.      When choosing a charge controller this is the number I need to determine if the Conext 80-600 is capable of handling the load. 


    I did not see Bills original post guiding you here, but suspect he is giving you the NOCT value at around 75-77%. Don't like Bill's numbers? Check your Spec sheet! Solar World predicts 213.1 Watts or 213.1 ÷ 285 or 75%

    PERFORMANCE AT 800 W/m², NOCT, AM 1.5  Maxximum Power 213.1 Wp
    So Solar world expects the panels to produce 213.1 watts under 'Normal Operating Cell Temperatures"

    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
  • BB.BB. admin Super Moderators, Administrators Posts: 29,634 admin
    He had sent me a pm asking about my magic numbers.

    MPPT controllers (at least the good ones) are designed to limit maximum output current and power.

    So, the 77% is the maximum cost effective over sizing I would suggest.

    However, electronics that from less than 100% rated output run cooler and last longer.

    And many controllers run fans, which can be pretty noisy.

    Choices in life we make.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini ✭✭✭✭✭ Solar Expert Posts: 4,753 ✭✭✭✭✭
    As Bill says with the age old Engineering reference that offgrid usage is very different from grid usage where outputs are at max all day with the sun out.  An offgrid system is rarely at max except the few hours that batteries are being charged and loads are running. Even then it is rare to be current limiting a controller offgrid.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

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