Morningstar TS-MPPT-45 maximum number of panels I can use

kevinhenrycalgary
kevinhenrycalgary Solar Expert Posts: 33
Hi All,

After my last post of four years ago I am again putting together another solar system. This time for a friends cabin as opposed to my original installation in a vintage trailer which has been working flawlessly for the past four years.

I just need a bit of a refresher before I start putting a system together for him.

I may purchase a Morningstar TS-MPPT-45 which has a 150 Volt maximum input voltage rating at worst-case and is capable of charging at 12, 24 and 48 volts.

I will be charging a 12 volt battery bank.

I will be using two 225 watt/24 volt panels and wish to wire them in series to charge at 48 volts. I don't have the exact panels just yet but lets assume they will have a Voc of 36.7 volts and a Vmp of 29.4 volts(numbers obtained from similar panel specs found on the internet)

Two panels wired in series will then allow me to charge at 48 volts with a Voc of 73.4 volts, about half of the maximum allowed by the TS-MPPT-45.

If I was to add more panels at a later date then

Four panels, wired in series/parallel will allow me to charge at 48 volts with a Voc of 146.8 volts. Still less than the maximum of 150 volts.

Four of these 225 watt panels would then be the maximum this controller could handle.


Am I thinking correctly or do I need to go back to square one and start learning again.

Thank you in advance for the guidance.

Kevin Johnston
Calgary, Alberta

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Morningstar TS-MPPT-45 maximum number of panels I can use

    You have a problem. The two panels in series will have a combined Vmp of 58.8, which is about the bare minimum for charging a 48 Volt system. Add to that reduction in Voltage from wiring resistance and reduction in Voltage from hot panels and you could find it insufficient to raise the batteries to full charging Voltage. Normally that would be around 58.4 minimum for flooded cells, with some requiring higher Voltage. Equalization would be impossible.

    Normally the Vmp for an array on a 48 Volt system is at least 70 Volts. I'd suggest either different panels or a third one in series (possibly lesser Wattage if that works). The Voc is not going to be a worry yet, even in Alberta. You'd have to be over 110 Volts before trouble may appear there.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Morningstar TS-MPPT-45 maximum number of panels I can use

    BTW the most panels the 45 Amp controller can handle on a 48 Volt system is more like 2800 Watts. That's more than ten 225 Watt panels.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Morningstar TS-MPPT-45 maximum number of panels I can use
    Hi All,

    After my last post of four years ago I am again putting together another solar system. This time for a friends cabin as opposed to my original installation in a vintage trailer which has been working flawlessly for the past four years.

    Welcome back to the forum Kevin--I take it your trailer system is still working well for you?
    I may purchase a Morningstar TS-MPPT-45 which has a 150 Volt maximum input voltage rating at worst-case and is capable of charging at 12, 24 and 48 volts.

    Nice controller... You might look at the 60 amp version if he would ever wish to run Internet on it (yea--a cabin--but who knows for remote monitoring).
    I will be using two 225 watt/24 volt panels and wish to wire them in series to charge at 48 volts. I don't have the exact panels just yet but lets assume they will have a Voc of 36.7 volts and a Vmp of 29.4 volts(numbers obtained from similar panel specs found on the Internet)

    For a 48 volt battery bank, you should be looking at ~Vmp-array of 72+ volts. The battery would need >60 volts charging (and more if it is sub freezing)--And Vmp falls as the panels get hot (Vmp can fall by ~20% in very hot weather--may be less of an issue in your region, but cold batteries are not).
    Two panels wired in series will then allow me to charge at 48 volts with a Voc of 73.4 volts, about half of the maximum allowed by the TS-MPPT-45.

    Voc is Voltage Open Circuit--I.e., no current flow. At the very least, you would need 3 panels in series for a reliable system that would charge at full array available wattage. Vmp (voltage maximum power) is the one we "care about" for moving electrons into the battery bank.
    If I was to add more panels at a later date then

    Four panels, wired in series/parallel will allow me to charge at 48 volts with a Voc of 146.8 volts. Still less than the maximum of 150 volts.

    Now, we have the "other problem" with system design. When the controller if "off" (batteries full), now the panels operate at Voc--And your sub freezing weather will take the Voc-array-cold well over the maximum input voltage of 150 VDC.

    Many controller manufacturers have "string calculators" for their products. Here is the one for Morning Star:

    http://www.morningstarcorp.com/en/strings/calc.php (hmm... Link is really slow for me at the moment)
    Four of these 225 watt panels would then be the maximum this controller could handle.

    I am guessing that for the panels you are looking at, 48 volt battery bank, and the "standard" 140-150 VDC max input controller--You can only run in strings of three (three in series, 2x 3 panel strings = 6 panels, etc.).

    While a good quality MPPT charge controller can handle an over-sized solar array (over size in terms of current--because MPPT controller do their own current/power limitation by design--safely and reliably), I would suggest the maximum "cost effective" array for a 45 amp controller would be:
    • 45 amps * 59 volts charging * 1/0.77 panel+controller derating = 3,448 watt max "cost effective array" on a 48 volt battery bank
    • 3,448 Watt array / 225 watt panels = 15 panels

    So arrays of 3/6/12/15 @ 225 watt panels would "make sense" for this controller/battery bank configuration (and you could go 18 and beyond, it is just the controller will spend more time "clipping" the available array power in the middle of the day).
    Am I thinking correctly or do I need to go back to square one and start learning again.

    Not back to square one--But brush on on MPPT charge controllers and what they need to be "happy".

    What is the size (AH @ 48 volt) is your friend looking at? A 2*225 watt array would suggest around a 120 AH @ 48 volt battery bank maximum (~5% rate of charge). That is a "relatively" small battery bank to choose to operate at 48 volts (i.e., finding a "small" 48 volt inverter).

    If the system power requirements are really that small (and do not need 48 volts to drive 48 volt DC loads), then reconfiguring to 12 volts and using a MorningStar 300 watt TSW inverter will be a really nice mix/match for cabin use (and a big/cheap MSW inverter to run the blender/well pump once in a while).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • kevinhenrycalgary
    kevinhenrycalgary Solar Expert Posts: 33
    Re: Morningstar TS-MPPT-45 maximum number of panels I can use

    Sorry, but I forgot to mention I am charging a 12 volt/220 amp hour battery bank and the cabin is located north of 60 degrees latitude near Yellowknife, Northwest Territories. Cold winter where minus 40C/40F is commom and very short days.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Morningstar TS-MPPT-45 maximum number of panels I can use
    Sorry, but I forgot to mention I am charging a 12 volt/220 amp hour battery bank and the cabin is located north of 60 degrees latitude near Yellowknife, Northwest Territories. Cold winter where minus 40C/40F is commom and very short days.

    I can see why you picked those two panels. But you might want to up the Wattage a bit more anyway, and perhaps set a current limit? (Not sure if the MS controllers can do that.) You have to get that array Vmp up or they aren't going to charge in Summer.

    Worst case in Winter will be about 1.3 * Voc, so you're still safe there even with three panels in series (Voc ~90 nominal).
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Morningstar TS-MPPT-45 maximum number of panels I can use

    Opps--Then 1/2/3 panels in series would be fine (as would 1/2/3 panels in parallel). In series, no combiner box/fuses/breakers required for 3 or more parallel panels).

    For maximum "cost effective array", basically 1/4 of that before:

    45 amps * 14.75 volts * 1/0.77 panel+controller losses = 862 watt array "cost effective maximum:
    • 862 watt / 225 watt panels = 3.83 panels ~ 4 panels "cost effective" maximum based on 45 amp controller
    • 220 AH * 14.75 volts * 1/0.77 losses * 0.13 rate of charge = 548 watt "cost effective max array" based on battery bank
    • 220 AH * 14.75 volts * 1/0.77 losses * 0.25 rate of charge = 1,054 watt recommended maximum array for battery bank

    Probably want to get the remote battery temperature sensor option too.

    Sorry--I was blind and missed the 12 volt bank...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Morningstar TS-MPPT-45 maximum number of panels I can use

    This is what threw us both off:
    Two panels wired in series will then allow me to charge at 48 volts with a Voc of 73.4 volts, about half of the maximum allowed by the TS-MPPT-45.

    With a 12 Volt system any array Vmp over 17 will work. You could wire the panels in parallel and increase the controller's efficiency. Cold temp Voc rise does not enter in to it then.

    The only reason to go with the panels in series is if there is a long wire run from array to controller. otherwise no advantage here.

    For reference: http://forum.solar-electric.com/showthread.php?16241-Different-Panel-Configurations-on-an-MPPT-Controller
  • kevinhenrycalgary
    kevinhenrycalgary Solar Expert Posts: 33
    Re: Morningstar TS-MPPT-45 maximum number of panels I can use

    Bill

    I had neglected to mention a 12 volt battery bank in my original post. I still had time to go back and edit it so it wasn't an Oops on your part. It was an Oops on my part.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Morningstar TS-MPPT-45 maximum number of panels I can use

    Not a problem Kevin.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Re: Morningstar TS-MPPT-45 maximum number of panels I can use

    Hi kevin,

    Well, as was indicated in previous posts, this CC may be a bit more than is needed for two PVs in this class.

    BUT, I am one that simply does not understand the use of these MorningStar CCs. $409. for a stripped CC. $90. for a midget display option, and, at least in the past, the MS Batt Temp Sensor was an additional $29 or so. All told, this would be in the price range of a full function Top-Of-The-Line CC, like the MidNite Classic 150 ... this, too, is overkill for this exact application:

    http://www.solar-electric.com/misoclchco.html

    The MidNite Classic will operate up to 150 V input, and will not be damaged when Vin is below 150 volts + nominal battery voltage -- 162-ish V in this case. But this would not apply to this exact situation with only two 30-ish V PVs ...

    A bit of a Thread Derail, I know. Nothing against the performance of the MS CCs, just EVERYTHING is an option at extra cost, IMHO.
    Derail end, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Morningstar TS-MPPT-45 maximum number of panels I can use

    For a smaller 12 volt system--I wonder if Rogue 12-48 30 amp MPPT controller is available yet:
    March 16, 2013 - Update. Circuit board assembly should be starting around the first or second week of April. We're waiting on availability of a few parts, with an ETA at end of March if the manufacturer doesn't push that back (as they've done once already). Turnaround on assembly is usually about three to four weeks on a new design, which will move us into May for controller availability.

    February 25, 2013 - Someone on another forum asked what the differences are between the new MPT-3048 controller and the older 3024 models. Here's a summary of the highlights:
    • Will support 12/24/36/48v battery banks
    • 100v max Voc PV limit
    • Battery sense wires are now optional (the 2nd gen 3024 required them)
    • Auto fault resolution (faults will not require the user to restart the controller)
    • Reverse battery and input short protection
    • User-upgradable firmware
    • Auto pass-thru on startup after initial setup (will power down/up and start charging without any user interaction after initial setup)
    • More extensive data logging and more real-time data accessible with the PC connection and software utility
    • Historical data log accessible via PC
    • Master-slave option for two controllers
    • Modified MPP tracking algorithm with new triggers for sweep and user-adjustable options
    • Real-time data always remains on display now, even during sleep
    • Adjustable battery temperature compensation
    • Adjustable current limiting
    • User-adjustable calibration
    • Slightly larger and heavier physically, more robust thermal design
    I'll have a full spec sheet out on the 3048 controller soon ... it's on the long list of things to do, but not toward the top quite yet. I'll post a link to it here as soon as it's available.

    Probably a bit far out there right now for your needs...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Morningstar TS-MPPT-45 maximum number of panels I can use

    Bill et al;

    Last update on the Rogue was availability in May.
  • kevinhenrycalgary
    kevinhenrycalgary Solar Expert Posts: 33
    Re: Morningstar TS-MPPT-45 maximum number of panels I can use

    Vic. I can get a good deal on a one year old Morningstar with remote meter as well as a good deal on the panels. This is why I am thinking of this particular combination.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Re: Morningstar TS-MPPT-45 maximum number of panels I can use

    OK Kevin,

    That is a very good reason ... Thanks, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.