Midnite Classic 150 - Turn Float Off ?

tr0ytr0y Solar Expert Posts: 96 ✭✭✭
Hi All - 

I am using a lithium based battery and the information available leans towards the battery not liking / it's unnecessary a float charge. I was wondering if any of the Midnite experts would chime in and give me some thoughts. 

Is there a way to or work around to turn float off ? I assume that at a specified SOC or voltage I would enter rebulk ? 

Thanks 

Comments

  • mike95490mike95490 Solar Expert Posts: 8,380 ✭✭✭✭✭
    You simply set your float voltage to below something the BMS is happy with. 
    To be real clever, don't go so low that the battery discharges when start the blender at noon, leaving you with half a charge at sunset

    And be sure to set ABSORB to only a couple minutes, generally that's all Li cells need.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • mcgivormcgivor Solar Expert Posts: 3,074 ✭✭✭✭✭
    The information available on LFP charging varies dramatically depending on application, much of which is related to EV applications and doesn't relate to solar off grid use. With EV the battery is charged to capacity then terminated, discharge only occurs when the vehicle is used, however in off grid there are likely loads which deplete the battery as soon as a nominal state is achieved usually capped at around 95%, to avoid the stresses of upper voltage charging.

    Without a float setting it would be possible that the battery reaches it's nominal fully charged state early in the day, if loads are present they would begin to discharge to a point of recharge voltage, this could be late in the day when there is insufficient sun to recharge. Having a float setting allows the battery to remain in a state of neither being charged nor discharged, but allows the PV to support loads until no longer capable, then it blends the two together until the PV terminates and the battery assumes all the load.

    My personal settings are a mirror of the recommendations of SimpliPhi' for maximum cycle life with Schneider equipment , despite being a DIY bank, they are as follows, 
    Bulk 28V
    Absorption 28V for 6 minutes 
    Float 27V
    Recharge 25V 
    Equalization disabled 
    Temperature compensation 0
    Programed capacity 0.5 of actual 

    Granted the controller is not Midnight but the settings could be programmed with such a sophisticated unit.
    Can you describe the battery in question, is it a DIY, a drop in replacement type and what chemistry because the battery may need specific requirements, there is no one size fits all, as with all battery types.
    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.
  • tr0ytr0y Solar Expert Posts: 96 ✭✭✭
    Thanks Guys ! I'll do some setting changes. 
  • mcgivormcgivor Solar Expert Posts: 3,074 ✭✭✭✭✭
    What batteries do you have? 
    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.
  • MrM1MrM1 Registered Users Posts: 450 ✭✭✭
    edited May 29 #6
    mcgivor,  does this lead to what some on YouTube had called "Micro Cycling" of Li batteries.  I responded to a negative YouTube video recently where the poster claimed Midnite and others lied about their diversion mode (seemed like strong language to me).  How it wasn't really a diversion and how in diversion mode (after fully charged),  the diversion would lead to Micro Cycling of the Li battery resulting in what would be (in the posters opinion) many extra complete cycles over the lifetime of the battery bank, thus shortening cycle life of the Li battery over time.  I wrote that while this might be true of Li chemistries,  this is not necessarily true FLA batteries as when diverting in float,  there is around 0.5 amps going to the battery all the time while the array is producing excess power to support  the load if the right solar conditions are available.

    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
  • mcgivormcgivor Solar Expert Posts: 3,074 ✭✭✭✭✭
    That is an interesting point which I can't definitively answer, but from observations with my system, there is little current sent to the battery as long as the array can support the loads, much the same as LA. Having said that there may be something to do with the BMS used, most have a single charge/ discharge port which doesn't allow bi directional current flow, this may, in some way result in micro cycles, if in fact this is an issue.

    This phenomenon brings up the question of EV dynamic braking, sending short bursts of energy into the battery, dose that constitute a micro cycle, and if so why would it be implemented as a benefit? 

    There are many unanswered questions, lithium technology depends largely on on electronics to safely control the parameters, I wonder if the chosen BMS is the pivotal factor, most applications are not geared towards off grid but rather to EV, which is very different in its dynamics.

    Perhaps some are attempting to translate EV applications to off grid, thus achieving results which are unexpected, thereby blaming the  equipment as incompatible for the supposed eronious outcome. 

    Just a collection of thoughts 
    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.
  • MrM1MrM1 Registered Users Posts: 450 ✭✭✭
    edited May 29 #8
    I know in the case of that one YouTube Channel,  he has a BMS ... BUT has chosen NOT to install it yet.  He is using used Telsa Batteries that have been in service for him for a year now.  I watch the channel and enjoy it, but take most of his methods with a grain of salt as they are often less than code compliant.  He does though have a separate detached battery building so if the batteries burst into flames he probably would not lose the house and would do no damage to other peoples property.
    And I don't know if you looked at the video,  but I do not feel like the manufactures of the Classic and Outback controllers have lied to us, but rather as you say,  Li batteries in Off grid is fairly new and there are unanswered questions.
    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
  • tr0ytr0y Solar Expert Posts: 96 ✭✭✭
    Thanks All ! 
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