Max charge rate of XW+ Inverter and charge limit of MPPT 60-150 Charge Controllers?

ligwydligwyd Registered Users Posts: 117 ✭✭
Hi there,

Just trying to get a clearer understanding of the Inverter and Charge Controller charge settings/ limitations.

I have "Cascading" selected on my SCP and as such (as far as I know as of now) when I select 10% max charge rate for my XW+ which I am gathering would be 63 amps max if batteries where discharged deeply(10% of my 630 AH battery bank), I notice the charge limit of 6.0 Amps (6.0 to 60 amp setting options) is automatically selected in the two solar Charge controllers which(6 amps is 10% of 60 amps of course). If I change the Solar charge controller to 60 amps charge limit I notice the max charge rate of the XW+ automatically adjusts to 100%. Just an observation. I don't actually charge at 100% of course.

Now whenever I turn on my system, if I am charging off the grid power, the XW will start in bulk and 13.8 amp is displayed on the Inverter screen and SCP screen. It shortly transitions from bulk to absorb and then float depending on how low the batteries are of course.

My questions are:
1. There are two different charging sources. The Solar Charge Controllers and the XW. Is the 6 amp charge controller limit from my charge controllers the same charging effect on the batteries as 10% max charge rate from my XW+?
2. Do I need to turn off cascading and manually set the inverter/ charger and each of my two charge controllers charging limits or is it functioning normally?
3. When my Inverter is displaying 13.8 amps in bulk is that at the voltage that the batteries are charging at? I am assuming so. I think that when the charger is in bulk and it is cold, the temp comp. bulk voltage is around approx 60 volts.
4. Why do I only see 13.8 amps Max my XW display? I guess I am trying to understand how 13.8 amps is the 10% max charge rate.... of what? Maybe my question would be answered if I discharge my bank 50% and see how many amps max it pulls to charge in bulk?

I'll call Schneider tech support in the morning and see if they can't straighten me out. Just thought I'd reach out to you guys since you guys have always been such a solid source of support which is very appreciated!

Comments

  • mcgivormcgivor Solar Expert Posts: 3,178 ✭✭✭✭✭
    The XW charging percentage is  not directly  related to the battery capacity, it is a percentage of the maximum charging current capacity, for example if the charger has a maximum charging current of 100A, 10% would be 10A, so for a 630Ah bank 60% would yeald 60A for a ~10% charge rate. The only time there is a relationship between the capacity entered and the charger is concerned is when AC is used to charge until float, to determine the 2% end amps,  usually in a grid supported system.

    The 60-150 controllers maximum charging current setting will limit the current to whatever it is set to, again not directly related to battery capacity, the only time this may be useful is if the array can supply more current than the battery can safety accept, for instance with a small capacity bank. The downside to the limitation is, it also limits the output which could potentially be used for loads if applicable. Again the capacity entered is to determine end amps.

    The cascading is a setting I'm not familiar with, perhaps favoring solar over grid cascading grid imput in relationship to solar imput? 

    Purposefully I've danced around the the questions because there is no indication of the actual system, state of charge and so forth, just attempting to explain how, I understand the primary settings to be. Hopefully this is helpful.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,844 ✭✭✭✭✭
    You could read the manual also!
    Cascading allows multiple devices to share settings. If you have a reason that you do not want them to share, and there are a few, do not enable cascading.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • ligwydligwyd Registered Users Posts: 117 ✭✭
    I'll just keep playing and gain experience as it all gets dialed in. I've poured through all the literature I have on all the equip but still finding a few areas of misunderstanding. I'll post when I get cleared up.

    Appreciate the time guys.

  • ligwydligwyd Registered Users Posts: 117 ✭✭
    Spoke with Schneider today. They recommended turning off cascading (after you have utilized that feature of course - of use when setting up more than one of the same piece of equip) and adjusting final charging settings on each piece of charging equip. separately. In my case, I have one XW+ and two MPPT 60-150 solar charge controllers.

    I'll ensure the XW is at 10% max charge rate and set the charge limit amps in the charge controllers to the max of 60 amps on each unit. This should hopefully ensure the XW and solar charge controllers all properly charge the batteries and also should not limit the through put of the solar charge controller to loads. I'll post how it works out tomorrow.
  • ligwydligwyd Registered Users Posts: 117 ✭✭
    mcgivor, after re-reading your comments I think you may have cleared up some of my misunderstanding. Takes me a bit but once I got it, I got it :)

    My XW+ MAX charge output is 140Amps as per specs. 10% of 140 is 14amps! Thats why my inverter only was displaying 13.8 amps max when charging from the grid. Got it! I thought the 10% max charge rate was 10% of my 630 AH battery bank and as such was confused...until now:)

    Now my batteries spec sheet says BULK (MAX) 0.20C20A which I believe is 20% of the C20 hour capacity of 210AH.
    So .20 X 210 = 42Amps.
    Now 42 amps is 30% of 140amps (XW max charge output) so I should be able to move up my XW max charge setting from 10% to 30% and then I will see more than 13.8 amps on the XW display when charging from the grid, provided batteries are needing a charge. I think that makes sense.

    Now, if I were to set my charge controllers to 42 amps max I should be OK. Not sure if my 4.7 kw array (6 strings of three panels each - 8.37 amps IMP x 6 = 50.22A) will even produce 42 amps but we'll see. I might even be able to leave my charge controllers set a 60 amps max and they should throttle down charging amps into the battery bank as necessary as per my last conversation with Schneider and not limit through put power to loads.

    Thoughts/ comments/ clarity muchly appreciated!



  • littleharbor2littleharbor2 Solar Expert Posts: 1,444 ✭✭✭✭
    If your battery bank is 630 ah. then you would aim for 10% @ 63 amps charging current, 126 amps @ 20%.  20% is the max charging current recommended for your AGM batteries but you don't necessarily need to charge at that high a rate.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • ligwydligwyd Registered Users Posts: 117 ✭✭
    Got it. 630AH battery bank. 10% max charge rate = 63A.
    63A of the 140A max charge capacity of the XW = 45% of the XW charge capacity.
    So I will set my XW at 45% max charge rate.
    I believe you can even charge at 5% of C20(would take longer to charge of course) but I keep hearing 10% is what to aim for so I'll go with that.
    Thanks
  • mcgivormcgivor Solar Expert Posts: 3,178 ✭✭✭✭✭
    The rational behind 10% minimum rule of thumb for full time off grid  is to take advantage of the limited solar window of opportunity, if the batteries can handle higher current it would be advantageous to increase the % in some cases. Similarly when using a generator the lower current would mean longer running hense more fuel. Some AGM batteries can take extremely high current, as do LFP which can be charged at 1C, or 630A for a 630Ah  battery, though it's probably not good to do so on a regular basis. Having grid to charge, a lower currentl would just mean a longer charge period, which is not generally a problem and probably less stressful on the batteries.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,844 ✭✭✭✭✭
    The 10% is also from old school wisdom on thermal cycling. Hitting a cold battery with max current will shorten it's life.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • ligwydligwyd Registered Users Posts: 117 ✭✭
    Thank you for your support :) I'll post any further clarification, of my misunderstanding, once I have made the necessary adjustments and have observed the outcome.
  • ligwydligwyd Registered Users Posts: 117 ✭✭
    So, all my questions have been answered, except for how the solar charge controllers will function, with out put settings set to MAX 60 amps, due to no sun right now.(but I'm sure they will operate as designed)

    To try and summarize:

    Turned cascading off and set max charge settings on XW and MPPT's separately. Solved.

    Set XW max charge rate to 45%, which is 63A max. Derived from 10% of 630AH battery bank and then 63 A of 140A (XW max charge rate) gives you the 45%.

    I was just thinking that 10% max charge setting on the XW was 10% of programmed battery bank AH capacity but its not, as you all have helped me clear up.

    Thanks once again for you help.
    Appreciate it.
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