Calb lifepo4 charge profiles and inverter settings

mahendra
mahendra Solar Expert Posts: 188 ✭✭✭
in Off Grid Solar & Battery Systems #1
Please recommend charge profiles for midnite classic and outback vfx 3648 for calb ca 180 ah .projected usage would not exceed 50% dod.
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #2
    @mahendra
    I also have an LFP bank and a Midnite Classic controller. If you don't have one already, I suggest getting a Whiz Bang Jr. 
    It integrates with the classic and is only about 50 dollars. It's very good battery monitor.
    For absorb, I have used settings between 54.8V and 55.2V with a float setting of 53.6V. I recommend the cells be top balanced. It is critical that the voltage of each cell be very close at the top of the charge. Let us know if you need assistance with that. 

    Rick 
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • mahendra
    mahendra Solar Expert Posts: 188 ✭✭✭
    #3
    Thanks I do have a whizbang jr.But how do you controller or monitor for low voltage disconnect on the inverter side.
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #4
    @mahendra
    You may be able to use the AUX 1 port dry contact on the Classic set as a low battery disconnect to power the inverter off via the inverter on/off switch connection. On the Radian I have, it's a jumper on a control board. Set to always on, or a toggle can be installed.
    I didn't think of that when I set mine up, so I used a JLD404AH Intelligent Ampere Hour Meter with a large 48 volt contactor. 

    Rick   
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #5
    It's a bit more involved, but I also plan to use a Raspberry Pi to poll Classic modbus registers, and disconnect large but non-essential loads (eg. pumps) at higher voltages than LBCO. As voltage drops, the rPi will open relays on progressively more important loads.

    This should help avoid hitting LBCO (and shutting everything down) at all. IIRC, my Outbacks have a switch port that can also be controlled by a simple relay, which could be flipped by the rPi as well, or by the Classic Aux port.
    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
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,894 ✭✭✭✭✭✭
    #6
    The outback inverter already has LBCO right?  Don't let your loads get that big or wait that long to charge the battery :)
    Have some headroom in the design!  Easy to say this before :)
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #7
    It does, but 48 volts is uncomfortably low for a 51.2 volt nominal LFP bank.
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,894 ✭✭✭✭✭✭
    edited January 2018 #8
    So adjust it? The inverter has adjustable LBCO? 

    Rick maybe the bank has one too many batteries and 48 is has high as LBCO will go?

    Seems like a battery design problem or is this an issue with Prismatics because of no BMS ? Typical LBCO is 44V and lights out!
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #9
    It would be nice if it the upper limit was above 48 volts. Of course, a 48 volt prismatic bank would have 15 cells and it would work fine with the inverter LBCO. Though it's always nice to have more storage. I like 16, then again 17 is good too. All can be done with no BMS, just have to innovate.

    Rick
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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