MX60 Clarification

I've been trying to decide how to upgrade my system (see Interstate Batteries post) and have questions about the controller. Is it able to handle different sizes of PV panels with only one unit? How much panel can you put through one? I'm currently using one Trace C40 to handle 6, 90 watt Siemens panels and another C40 to handle 3, 120 watt Kyocera panels and plan to add 3 more 120's (actually 130's). It would really be nice to be able to simplify and just let one MX60 do it.

Thanx

Dennis Webster
Bagdad, Az

Comments

  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: MX60 Clarification

    Dennis,

    The MX60 is somewhat conservatively rated by OutBack to handle a PV array rated at ~1,600 W STC when charging a “24 V” battery bank. Adding the additional three KC-130 modules will increase your array’s STC power rating to 1,290 W – well within the MX60 capabilities.

    Its power handling capabilities for 12 V and 48 V systems are ~800 W STC and 3,200 W STC, respectively.

    It’s generally OK to mix ’n’ match PV modules from various manufacturers into a single large PV array feeding a single controller. Overall performance can be compromised depending on individual module specs. Although you’re planning on an array of three different modules sizes, you’re also planning on three identical modules within each of the four series strings, so that will help minimize any problems.

    Here’s what I believe are the important specs for your various modules:

    Siemens SR90: 90 W STC, 17.0 Vmp, 5.4 A Imp each; 270 W STC, 51.0 Vmp, 5.4 A Imp in a series string of three modules (voltages add for modules in series, and series string current = current of lowest rated module.)
    Kyocera KC-120: 120 W STC, 16.9 Vmp, 7.10 A Imp each; 360 W STC, 50.7 Vmp, 7.10 A Imp in a series string of three modules
    Kyocera KC-130: 120 W STC, 17.6 Vmp, 7.39 A Imp each; 390 W STC, 52.8 Vmp, 7.39 A Imp in a series string of three modules

    PV module cells heat up when exposed to the Sun, so their voltage drops. Accordingly, ~88% of STC Vmp is a good working voltage. The working Vmp’s for your various strings will be ~44.5 V, ~44.5 V, and ~46 V. When all of the series strings are connected in parallel, the array will operate at the lowest string voltage. So, look for the array to operate at ~44.5 V -- perhaps a bit lower in summer and a bit higher in winter -- when the controller is in bulk stage.

    The total array current at ~mid-day on a sunny day will be the sum of each string current: 5.4 A + 5.4 A + 7.10 A + 7. 39 A = ~25 A. While the KC-130 modules will operate at somewhat less than optimal due to the lower voltage of the other strings, their slightly higher current rating will result in performance that’s a bit better than that of the KC-120’s.

    In sum, the MX60 will be able to comfortably handle your planned 1,290 W STC array and 24 V battery bank, its DC-DC conversion feature will take the ~44.5 V x ~25 A in and convert it to ~29 V x 36 A out (bulk stage; assumes ~94% efficiency), and its MPPT feature will make the most of environmental conditions in producing the greatest amount of power available from the array.

    HTH,
    Jim / crewzer
  • backroadbackroad Solar Expert Posts: 185 ✭✭
    Re: MX60 Clarification

    WOW! there you go again crewzer, show'n off. You definitely have a bundle of information lodged in your head. Must get kind of crowded in there at times. :):):)

    You and NAWS have now sold me on the Outback 3524 and the MX60. Now all I have to do is decide whether to go with the T105 type of battery and use 16 of them or go with the L16 and go with 12 of them. AND then decide if I need to go cheap and save a measely thousand dollars and use the Interstate batteries instead of the Crown, or trojan or Rolls ETC.

    Thanx again for your valuble time.

    Dennis in Bagdad :-P :-D 8-)
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: MX60 Clarification

    Dennis,

    Glad to help. Yeah, it does get a bit crowded in the ol' noggin on occasion, but I'm slowly learning to just remember what info I need, where to get it, and how to interpret it rather than just memorize a bunch of stuff and not understand it. I also find it much more satisfying to explain and justify my assessments and recommendations to the forum. In doing so, I hope that other members will be able to understand how to analyze and tackle their individual design challenges.

    I'd recommend L-16 batteries over the T-105's. Why? A smaller overall "footprint" for the batteries, fewer battery interconnect cables (lower probability of failure, less maintenance), fewer cells to maintain (12 x 3 = 36, vs 16 x 3 = 48).

    However, L-16's might need a special charging algorithm. See the following reference:

    http://www.morningstarcorp.com/products/TriStar/info/TS_Manual.pdf (page 48)

    HTH,
    Jim / crewzer
  • backroadbackroad Solar Expert Posts: 185 ✭✭
    Re: MX60 Clarification

    Does this mean that I'd need to add a separate CHARGE CONTROLLER?
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: MX60 Clarification

    Dennis,

    No, you won't need a separate charge controller. The MX60's target voltages for the absorb-, float-, and EQ stages can be user-set to the values you'll need. The point of the reference above is that it's different from the settings recommended by Trojan for their batteries.

    Regards,
    Jim / crewzer
  • MangasMangas Solar Expert Posts: 547 ✭✭✭✭
    Re: MX60 Clarification

    With my two Outback M60s', I'm running 40 x 185W panels and 68 Trojan wetcells split into two banks.  These controllers are very flexible.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
  • backroadbackroad Solar Expert Posts: 185 ✭✭
    Re: MX60 Clarification

    Mangas, I just went back and reread your post. My goodness guy, 40 panels and 68 Trojan batteries. What are you running? A small town?
  • MangasMangas Solar Expert Posts: 547 ✭✭✭✭
    Re: MX60 Clarification

    Almost.  I put my ranch into conservation and do not want any infrastructure near it as we are bounded on three sides by the National Forest, Wilderness and state public lands.  The only real way to protect the land and the help preserve desert mountain landscapes was to set up the ranch house utilities, wells, etc to run off grid solar. 

    The system is putting out a tremendous amount of power enough to run everything including our two 2 1/2 ton central air conditioning and heating zones.  During the day the panels seem to run everything ok and at night the battery banks easily have handled the furnaces and peak power consumption. 

    We did disconnect the heat pumps because we found they were inefficient from a power consumption standpoint.  The dual fuel Trane propane variable speed furnaces were able to handle eveything better on their own.  Even though we are running four Xantrex Sineplus SW 5500W Inverters, we still had to install motor run capacitors on the furnace units to get them to run properly.

    This summer we'll see how we do with reserve battery levels after A/C consumption but last fall eveything ran fine.  With longer days this summer and our unobstructed SE sun angle we're targeting battery voltages of 47V - 49V at sunup.  We don't have trackers on the panels and don't seem to need them.

    The solar people designed the system to run with the standby generator charging the batteries only on an emergency basis. My design criteria was to have the panels run everything during the day and the batteries at night with total power output capacity to be 120% on our needs.  We have two 100 amp AC service panels at the house with each zone into separate panels for redundancy purposes.

    Forgive the little off topic.


    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
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