Which Mppt Charge Controller

Jcrabtree
Jcrabtree Registered Users Posts: 24 ✭✭✭
Have 2 Kyocera Solar KD-135GX 135 Watt 12 Volt panels - wanted a decent mppt with room to upgrade for the future

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Which Mppt Charge Controller

    Welcome to the forum.

    How much upgrading are you thinking about?
    You could get a Morningstar 45 Amp MPPT or 60 Amp MPPT, also Outback FM60 (60 Amp) or FM80 (80 Amp) or Xantrex 60 Amp or Midnight Solar 150 or 250. Each has its own advantages and disadvantages.

    To really make the determination, you need to plan out your system now and what you want it to be in the future. That's the best way to determine what controller can fit the bill best for both systems.

    Note I have purposefully left out the Rogue and BlueSky controllers because they are not very "upgradable" - having input Voltage limitations. The ones mentioned allow at least 150 Volts on the input side and can support system Voltages of 12, 24, or 48 at the least.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Which Mppt Charge Controller

    What battery bank voltage (12/24/48 volts)?

    A list of controllers to look at:
    1. MorningStar 15 amp MPPT 12/24 volt
    2. Rogue ~30 amp 12/24 volt MPPT (new model due June 1)
    3. Morning Star 45 and 60 amp MPPT TS series (12-48 volts)
    4. Midnite Solar Classic ~80 Amp MPPT (new to market--same designer as Outback FX series) (12-48 volts)
    5. Xantrex 60 MPPT (new high voltage to 600 VDC unit due out soon)? (12-48 volts)
    6. Outback FM 60/80 MPPT (12-48 volts)
    What features are you looking for? Networking, logging, 150 VDC maximum Vpanel input, price, etc.? Ability to place the Solar Array a long distance from charge controller/battery bank?

    Problem is that you should probably plan on picking a controller that is 2x larger than your initial array (if you plan to grow)... Small arrays on large controllers are not very efficient (especially on MPPT controllers).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Jcrabtree
    Jcrabtree Registered Users Posts: 24 ✭✭✭
    Re: Which Mppt Charge Controller

    Will be for a small off grid cabin - will be done in 2-3 months, wanted to start off with something small and work my way up - Batteries that I'm looking @ Trojan L16RE-B or SunXtender PVX-3050T AGM - x2 @ start - my goal is to have 8 to account for 2-3 days without sunlight - plus another 4 panels 135watts

    Been researching mppt for awhile - outback 80 mppt was looking good till seen the forums a lot of ppl are saying the buttons doesn't work after awhile - any opinion would be great help - I'm torn between which mppt to go with - want something that will last.
  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
    Re: Which Mppt Charge Controller

    I think as far as reliability goes, about any one of those in the list will work well.

    One can get a lemon in any particular manufacturer's products, but in general, these are all pretty good controllers.

    I am surprised top hear that buttons have been any kind of an issue for an OutBack product though. Maybe some contamination got on the PCB under the buttons ??

    boB
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Which Mppt Charge Controller

    Before picking specific hardware--I would suggest getting a basic system sizing together first.

    I assume that you have done everything you can for energy conservation? A good starting rule of thumb is to plan on your off-grid (with generator backup) power to cost you in the range of $1-$2 per kWH (or more, if this is not a full time residence). So--anything you can do (or spend) to reduce electrical usage will usually be a good investment.

    I like 48 volt systems for large battery banks (and, I assume, large inverters). 24 volt would probably OK too--with two strings of batteries in your bank.

    Energy storage:
    • 8 batteries * 6 volts * 370 AH = 17,760 Watt*Hours of storage
    Assuming 3 days of no sun, 50% maximum discharge (for long battery cycle life) and an 85% efficient inverter, your daily WH load appears to be:
    • 17,760 WH * 1/3 days no sun * 0.50 maximum discharge * 0.85 efficient inverter = 2,516 WH per day
    Using PV Watts, Nashville TN, assuming fixed array, 0.52 overall derating and a round number of 1,000 Watt array:
    "Station Identification"
    "City:","Nashville"
    "State:","Tennessee"
    "Lat (deg N):", 36.12
    "Long (deg W):", 86.68
    "Elev (m): ", 180
    "PV System Specifications"
    "DC Rating:"," 1.0 kW"
    "DC to AC Derate Factor:"," 0.520"
    "AC Rating:"," 0.5 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 36.1"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:"," 6.9 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 3.62, 57, 3.93
    2, 4.32, 62, 4.28
    3, 5.25, 81, 5.59
    4, 5.53, 78, 5.38
    5, 5.63, 80, 5.52
    6, 5.95, 79, 5.45
    7, 5.99, 82, 5.66
    8, 5.68, 79, 5.45
    9, 5.27, 71, 4.90
    10, 5.07, 73, 5.04
    11, 3.63, 53, 3.66
    12, 3.22, 49, 3.38
    "Year", 4.93, 843, 58.17
    Assume 3 months a year, you will use a genset... that leaves February as your "transition" month between solar and genset use:
    • 62 kWH per month * 1/28 days per month = 2.21 kWH = 2,210 WH per day per 1,000 watts of panels
    • 2,516 WH per day needed / 2,210 WH per 1,000 watt of panels = 1,136 Watts of panels
    Now, a battery bank should have around 5% to 13% rate of charge from the solar panels (large banks need larger solar arrays for proper charging):
    • 8 batt * 6 volt * 370 AH * 1/0.77 panel+controller derating * 0.05 rate of charge = 1,153 Watts minimum solar panels
    • 8 batt * 6 volt * 370 AH * 1/0.77 panel+controller derating * 0.10 rate of charge =2,036 Watts good sized array
    • 8 batt * 6 volt * 370 AH * 1/0.77 panel+controller derating * 0.13 rate of charge =2,998 Watt rough maximum cost effective solar array
    So, an array to support your final battery bank size would be roughly 1,200 to 3,000 watt solar array...

    If you want to start with two batteries--then take the above numbers and divide by 4 (daily loads, and solar PV array sizing).

    Note--Enlarging a system by 4x is not very easy or cost effective... About the only thing that can be "saved" is the MPPT charge controller as most can be support 12/24 or 12/24/48 volt battery banks. Charge controllers are rated at maximum output (like 60 amps)--So if you start with a 12 volt bank, going to a 24 volt bank, the solar charge controller can manage 2x the amount of panels:
    • 60 amps x 14.5 volts charging * 1/0.77 derating = 1,130 Watt array @ 12 volt bank
    • 60 amps x 29.0 volts charging * 1/0.77 derating = 2,260 Watt array @ 24 volt bank
    • 60 amps x 58.0 volts charging * 1/0.77 derating = 4,520 Watt array @ 48 volt bank
    Anyway--the above is my guess at what you are asking for.

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