Can two Midnite Solar Classic 150 be used in parallel?

SaiproSaipro Solar Expert Posts: 74 ✭✭
I'm referencing this 2012 thread: Can you use two separate MPPT charge-controllers http://forum.solar-electric.com/foru...=1437804891996

I'm helping a friend with his off-grid plans and he wants to use two (2) Midnite Classic 150 in parallel to charge a common bank. I've scoured the web and found instances of attempts on it but nothing regarding the practical application. Can anyone help with this information? Thanks
Semi off-grid

255W Canadian Solar × 12, 200AH 48V US 185 XC2 bank, Victron Bluesolar MPPT 150/85, Victron CCGX, Victron MultiPlus 48V/5kVA/70A inverter (primary system) Victron Phoenix 48V/375VA inverter (backup for critical loads)

300W Yingli × 2, Midnite Brat, 200AH 24V bank (powers DC LED security lights)

Comments

  • boBboB Solar Expert Posts: 965 ✭✭✭✭
    Depends on what you mean by parallel. If you mean can you put two Classics on ONE battery bank, then yes, of course. But if you mean, can you put one large PV array into TWO Classic INPUTs, the answer is no. You can parallel the battery outputs but not the PV inputs of two Classics. Each Classic must have its own PV array input.
  • SaiproSaipro Solar Expert Posts: 74 ✭✭
    Yes, I meant putting two classics onto one battery bank. Now, read somewhere (speculative) about one CC sensing current in such a way that it recognizes the current in both the bank and that coming from the other CC as being bank current hence being unable to give optimal (or giving sub-optimal) current output. Does this mandate the networking of the Classics?

    The real life application is this:
    The entire is meant to provide inline backup for a hotel's lighting. The DC side primarily consists of
    - Trojan IND17-6V 925Ah x 8 for a bank at 48V with 925Ah capacity
    - 240W Joy Solar JYSP-240 PV panels x 40 in 2 arrays of 20 panels (4800W) to feed one CC each
    - Midnite Classic 150 CC x 2

    The whole point is to at least hit the 13% charge current once a week during the monsoon months when the skies are overcast most of the time with 2 - 3 hour lucky breaks. What do I need to do?
    Semi off-grid

    255W Canadian Solar × 12, 200AH 48V US 185 XC2 bank, Victron Bluesolar MPPT 150/85, Victron CCGX, Victron MultiPlus 48V/5kVA/70A inverter (primary system) Victron Phoenix 48V/375VA inverter (backup for critical loads)

    300W Yingli × 2, Midnite Brat, 200AH 24V bank (powers DC LED security lights)

  • westbranchwestbranch Solar Expert Posts: 5,142 ✭✭✭✭
    you need more info, such as to the daily depth of discharge and days of autonomy you have planned for, backup generator , inverter and the peak loads to be handled...
    hth
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • SaiproSaipro Solar Expert Posts: 74 ✭✭
    I have those other details worked out, hence the sizing of the banks and the number of panels required to charge back fully in one day as well as supply a liitle extra punch during the clear sky harmattan season. It's the configuring of the Classics that seems to be my Achille's heel. Can I just hook them up in parallel to feed the same back straight out of the box or must I network them to each other?
    Semi off-grid

    255W Canadian Solar × 12, 200AH 48V US 185 XC2 bank, Victron Bluesolar MPPT 150/85, Victron CCGX, Victron MultiPlus 48V/5kVA/70A inverter (primary system) Victron Phoenix 48V/375VA inverter (backup for critical loads)

    300W Yingli × 2, Midnite Brat, 200AH 24V bank (powers DC LED security lights)

  • BB.BB. Super Moderators, Administrators Posts: 29,482 admin
    With MPPT controllers, you can connect both to a single battery bank (I recommend that each controller have its own wire run--Don't "daisy chain" the controllers--Battery to controller A to controller B).

    Each MPPT controller should have its own solar array input (you cannot share one solar array with two or more MPPT type charge controllers).

    You don't have to network them together--What will happen is that the transition from Bulk to Absorb to Float will not be "identical"--One will change modes before the other. This is not a problem, but minor voltage/timing variations will cause this to happen.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SaiproSaipro Solar Expert Posts: 74 ✭✭
    Thanks Bill. Wasn't willing to found out raw if it wouldn't work. The cost of the equipment/investment could bring a man to his knees should things go south.
    Semi off-grid

    255W Canadian Solar × 12, 200AH 48V US 185 XC2 bank, Victron Bluesolar MPPT 150/85, Victron CCGX, Victron MultiPlus 48V/5kVA/70A inverter (primary system) Victron Phoenix 48V/375VA inverter (backup for critical loads)

    300W Yingli × 2, Midnite Brat, 200AH 24V bank (powers DC LED security lights)

  • VicVic Solar Expert Posts: 2,970 ✭✭✭✭
    Saipro,

    The MidNite Classics can be "Networked", so that they can share the same Charge State. This networking is via a Phone Cable -- standard four-conductor. So each Classic should be located close to the other.

    This interconnection and the communication function between the Classics is called ' Follow Me '. There is no specific communication or process that will cause the two Classics to share the charging power delivered by each CC. But having the two CCs share the Charge State is a huge advantage.

    One fairly common frustration with more than one CC that do not have the Follow Me capability, is that one will decide that it is time to go to Float, stranding the other CC/s in Absorb. Without the power contribution of the CC that just went to Float, the stranded CC often cannot maintain the set Absorption voltage, and it reverts to Bulk for the rest of the day. This is not a real big deal, but it can result in increased water consumption, and perhaps can add a certain amount of additional Plate Erosion, etc, IMO.

    FWIW, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 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.
  • Ethan BrushEthan Brush Solar Expert Posts: 231 ✭✭
    Vic wrote: »
    Saipro,

    The MidNite Classics can be "Networked", so that they can share the same Charge State. This networking is via a Phone Cable -- standard four-conductor. So each Classic should be located close to the other.

    This interconnection and the communication function between the Classics is called ' Follow Me '. There is no specific communication or process that will cause the two Classics to share the charging power delivered by each CC. But having the two CCs share the Charge State is a huge advantage.

    One fairly common frustration with more than one CC that do not have the Follow Me capability, is that one will decide that it is time to go to Float, stranding the other CC/s in Absorb. Without the power contribution of the CC that just went to Float, the stranded CC often cannot maintain the set Absorption voltage, and it reverts to Bulk for the rest of the day. This is not a real big deal, but it can result in increased water consumption, and perhaps can add a certain amount of additional Plate Erosion, etc, IMO.

    FWIW, Vic

    It is nice that the classics have the follow me feature. I would think that should be a standard feature from all manufacturers - seems like a no brainer to me..... Here is a white paper from Morningstar discussing paralleling multiple controllers (their controllers do not communicate with each other).

    http://www.morningstarcorp.com/parallel-charging-using-multiple-controllers-separate-pv-arrays/

  • SaiproSaipro Solar Expert Posts: 74 ✭✭
    Vic wrote: »
    Saipro,

    The MidNite Classics can be "Networked", so that they can share the same Charge State. This networking is via a Phone Cable -- standard four-conductor. So each Classic should be located close to the other.

    This interconnection and the communication function between the Classics is called ' Follow Me '. There is no specific communication or process that will cause the two Classics to share the charging power delivered by each CC. But having the two CCs share the Charge State is a huge advantage.

    One fairly common frustration with more than one CC that do not have the Follow Me capability, is that one will decide that it is time to go to Float, stranding the other CC/s in Absorb. Without the power contribution of the CC that just went to Float, the stranded CC often cannot maintain the set Absorption voltage, and it reverts to Bulk for the rest of the day. This is not a real big deal, but it can result in increased water consumption, and perhaps can add a certain amount of additional Plate Erosion, etc, IMO.

    FWIW, Vic

    Yeah, I saw the "follow-me" feature but didn't consider the significance until you mentioned it. It's true (theoretically) that one CC could be stranded in absorb/bulk (why didn't that ever occur to me?)

    Unless I get other counter-ideas/counter-suggestions, I guess follow-me it is. Seems you understood my question better than even I
    ;)
    Semi off-grid

    255W Canadian Solar × 12, 200AH 48V US 185 XC2 bank, Victron Bluesolar MPPT 150/85, Victron CCGX, Victron MultiPlus 48V/5kVA/70A inverter (primary system) Victron Phoenix 48V/375VA inverter (backup for critical loads)

    300W Yingli × 2, Midnite Brat, 200AH 24V bank (powers DC LED security lights)

  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Follow me works good, but its not really the end of the world without it. Just calibrate both controllers voltage settings to within 0.1V (do need an adjustable controllers for this, but you need that anyway, right...). The differences will only kick in when the controllers start to throttle back later in the charge stages. During bulk both will work as hard as each other, sourcing current with the battery dictating the voltage of everything.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    zoneblue wrote: »
    FDuring bulk both will work as hard as each other, sourcing current with the battery dictating the voltage of everything.
    Which does bring up the potential problem of excess Bulk stage current into the battery bank unless the array power limits it sufficiently.

    SMA SB 3000, old BP panels.
  • SaiproSaipro Solar Expert Posts: 74 ✭✭
    inetdog wrote: »
    Which does bring up the potential problem of excess Bulk stage current into the battery bank unless the array power limits it sufficiently.

    Hmm. Pretty interesting stuff. My first post on this forum addressed the concern of oversizing an array to forestall the "sunless"/cloudy days, as they prove to be the Achille's heel of any PV system. I was reassured by emminent members that I had little to worry about. Indeed, they were proved right (though I eventually beefed up the bank size).

    On my own setup which utilizes Trojan T105-RE batteries, I seem unable to force more than 13% of their rated capacaity in as charging current during bulk mode (unless discharged to about 40% in which case I get up to 17% for a brief run while things are settling down). I guess that's part of the "smart" battery design.
    Semi off-grid

    255W Canadian Solar × 12, 200AH 48V US 185 XC2 bank, Victron Bluesolar MPPT 150/85, Victron CCGX, Victron MultiPlus 48V/5kVA/70A inverter (primary system) Victron Phoenix 48V/375VA inverter (backup for critical loads)

    300W Yingli × 2, Midnite Brat, 200AH 24V bank (powers DC LED security lights)

  • PhotowhitPhotowhit Solar Expert Posts: 4,994 ✭✭✭✭
    But does the battery dissipate the excess as heat?
    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
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Photowhit wrote: »
    But does the battery dissipate the excess as heat?

    As long as you do not exceed the nominal Bulk voltage, the higher current will heat the battery somewhat, enough to potentially cause thermal runaway problems if the CC does not use a remote temp sensor.
    And the charging efficiency will be lower since there will likely be excessive gassing.
    But a good portion of the excess current above the C/8 rule of thumb limit for FLA will actually go to charging the battery faster. It will just be reducing the battery cycle life disproportionately in the process.

    The behavior you notice is not part of smart battery design, it is just a result of the terminal voltage and internal resistance of battery as functions of the State Of Charge (SOC).
    SMA SB 3000, old BP panels.
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