Another question on Conext XW+ Grid Support Voltage

neutronspinneutronspin Registered Users Posts: 51 ✭✭

Hello

This is my off-grid setup:

Schneider XW+6848 Inverter

7.2 kw solar array/24 Mission Solar 300 watt panels

2- Schneider MPPT60-150 controllers

Conext SCP

Conext Battery Monitor

Conext ComBox

48volt 430ah flooded lead acid battery bank

I wish to run my system in grid support mode with solar at top priority. And no selling to the grid. I have the grid support enabled and the support voltage set at 49 volts, 2-stage charge cycle, Recharge voltage 50 volts, Charger float voltage 54 volts. At night when there are minimum loads the charger seems to come on every hour or so trying to keep my batteries at 100% which I assume is correct. Would a larger capacity battery bank reduce the cycling at night? Here is a chart of the battery charge:

As you can see during the day the battery bank is kept at 100% from small amounts of solar and the rest of the loads are supplied by solar. Would increasing the battery bank size minimize the charging from the grid at night? My array during the day is more than capable of handling the daytime loads and unless I am using more than average loads during the day never exceeds 5.0kwh...usually somewhat less.

Any info appreciated since this is a new system after replacing my SW4048 inverters with the XW+ which is head and shoulders above the SW's. Any suggestions on my settings would be appreciated. Thank you.

Comments

  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭

    Program a charge block during the hours when charging is not needed.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • neutronspinneutronspin Registered Users Posts: 51 ✭✭

    Thanks...I am still getting familiar with the settings....will try that and see the results...thank you...

  • MrM1MrM1 Registered Users Posts: 487 ✭✭✭✭

    A charge block will work, but if you are solar charging, why not turn off the XW charger off (unless you are just trying to stay in float service and not discharge at all) Then by day you will charge and run loads, and at night you will power loads and if needed if the battery voltage drops below your desired set point, the "balance of power" being supplied will switch to the grid until the next solar charging cycle. You are using a lot of unnecessary grid power (IMHO) to charge via the XW, when you really dont need to.

    REC TwinPeak 2 285W 3S-3P 2.6kW-STC / 1.9kW-NMOT Array / MN Solar Classic 150 / 2017 Conext SW 4024 Inverter latest firmware / OB PSX-240 Autotransfomer for load balancing / Trojan L16H-AC 435Ah bank 4S connected to Inverter with 7' of 4/0 cable / 24 volt system / Grid-Assist or Backup Solar Generator System Powering 3200Whs Daily / System went Online Oct 2017 / System, Pics and Discussion
  • neutronspinneutronspin Registered Users Posts: 51 ✭✭
    edited April 2019 #5

    I tried doing that with my SW4048 and it caught on fire...really...so I am hesitant to cycle the grid power off and on. It should work like you said but I am not sure my battery bank @ 430ah is sufficient. I had installed a relay that was triggered by my MPP60-150 charge controller that would automatically open the grid supply at a specific setpoint with enough hysteresis but not sure what happened but the inverter was toast after a few days. There is an application note I found from Schneider (976-0321-01-01 rev A) that I will try to implement to improve my solar priority since the present settings are constantly trying to keep my battery bank at 100%. I run the inverter in Grid support mode with no sellback......Did you mean to turn off the grid support feature and put the charger in disable and rely on just solar to run my loads?........That would be an interesting experiment but don't know if the battery bank would keep up at night.......thanks for the info....

  • EstragonEstragon Registered Users Posts: 4,496 ✭✭✭✭✭

    Just a thought, but maybe set float to ~50.5-51v? That's roughly where a full bank will settle at with no load or charging source. At 54v, the charger has to charge to keep the bank from settling down to fully charged resting voltage, even with zero load on the bank.

    If you hit the 50v recharge and do a charge cycle somewhat regularly, I don't see how float charging is really doing much anyway.

    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • SolfyrSolfyr Registered Users Posts: 22 ✭✭

    7.2 kW array may supply 6 hours * 3 kW = 18 kWh into a BatteryBank of 400 Ah * 50 V = 20 kWh .


    When discharged to 50 % DoD , then those 18 kWh would be plenty .


    But of course , a larger Battery will also just be drawn the same amount of kWh , as before ...

    So , assuming a bank of 540/48 ≈ 500 Ah * 50 V and 25 kWh , will be less discharged down to 15 kWh , instead of 10 kWh .


    The solar would still produce for the grid .


    Though the "30 silverlings" might be not the best number in special environments , it would be therefore not too bad to upgrade , especially , when the batteries are 5 years and more in service .


    For the nighttime recharge , I estimate some 1.5 to 3.0 kWh grid usage , looking at those rafters averaging 0.06 * 30 each night ; thats then ~1 MW each year at $0.1 ≈ $100,- annually . Not sure , if $500 over a 5-year timespan would be worth it , to invest into a larger battery , or toasting a setup , that works .

  • MrM1MrM1 Registered Users Posts: 487 ✭✭✭✭

    Your SW caught fire! Crazy scary!

    No I was referring to leaving grid supply on and charger off.

    REC TwinPeak 2 285W 3S-3P 2.6kW-STC / 1.9kW-NMOT Array / MN Solar Classic 150 / 2017 Conext SW 4024 Inverter latest firmware / OB PSX-240 Autotransfomer for load balancing / Trojan L16H-AC 435Ah bank 4S connected to Inverter with 7' of 4/0 cable / 24 volt system / Grid-Assist or Backup Solar Generator System Powering 3200Whs Daily / System went Online Oct 2017 / System, Pics and Discussion
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