2 stage no float, Bulk-Absorb-Float

StevenB
StevenB Solar Expert Posts: 71 ✭✭✭✭
Can someone start me to understanding the principle of 2 stage no float, Bulk-Absorb-Float?
Especially Float.....and what's the difference between the Controller and Inverters separate roles in "Float"?

Thanks,
Steven

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 2 stage no float, Bulk-Absorb-Float

    Normally, when a battery is significantly discharged (below ~90-80% state of charge), a charge controller will output the maximum designed/available current to the battery bank (quickest charging).

    Once a battery is near fully charged, then the current is cut back a bit to prevent the battery from overheating/outgassing hydrogen from too high of charging current.

    Float Charge--is just enough voltage required to keep the battery fully charged, but not bubble off much hydrogen gas. Generally, float charging is most useful on systems that will sit for weeks or months between usage (batteries sit at full charge for long periods of time).

    If you don't have a "float mode" charger and the bank is lightly used, it may use more distilled water every month than one on a controller with a "float charge mode". Note that AGM/Sealed batteries are not intended to be refilled with distilled water and if the battery is overcharged and "vents"--then it is usually a short time from being recycled.

    Correct battery charging voltages are temperature sensitive (battery voltage rises as the become cooler--however their capacity also decreases as the batteries get cold). Also, flooded cell batteries will freeze closer to 32F the closer they are to discharged/dead (which will crack the case for flooded/sealed batteries).

    As in the other post--Here is a Battery FAQ link.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: 2 stage no float, Bulk-Absorb-Float

    There is a great charge controller FAQ here:
    http://www.windsun.com/ChargeControls/ChargeCont.htm

    and a battery FAQ here:
    http://www.windsun.com/Batteries/Battery_FAQ.htm

    Both have section on battery charging and explain what happens at each stage. In RE systems, there is not much time spent in "float" unless you are on vacation.
    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
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  • StevenB
    StevenB Solar Expert Posts: 71 ✭✭✭✭
    Re: 2 stage no float, Bulk-Absorb-Float

    Thanks! Here's my confusion....
    I have a Xantrex 6048 hybrid, BZ 500 controller, and 16-12v/100amphr batteries ....but for now just 2 60 watt kanekas, and 1 airx 400. My goal was to learn the science of all this stuff, with a few power components, then expand after I have some learning (200w panels w/ Xantrex Controller, plus Whisper 200's).

    But as a beginner I am still confused on the basics:
    I turned the float adjustment up on my controller to compensate for the few number of panels....so now in my understanding it is allowing more PV amps "in" ...and the float light that was on all the time, is off. So if it is not floating (no float led light illuminated), and my Pentametrix monitor says I am taking in more amps...how does that square with your description of "float" as maintenance charging from the solar pv? I hope this is even somewhat coherent...I get confused just writing it.

    Also...if my Inverter is set for 2stage No Float, does my Float charge setting affect anything?
    Thanks in advance for your patience,
    Steven
  • StevenB
    StevenB Solar Expert Posts: 71 ✭✭✭✭
    Re: 2 stage no float, Bulk-Absorb-Float

    Mike,
    Your info came in while I was replying to BB. Thanks I will study this.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 2 stage no float, Bulk-Absorb-Float

    Steven,

    Sorry--it is going to get more complex here...

    Are you setting up for a Grid Tied feed with your XW inverter?

    If so, then you want the battery charge controller to not have a float mode... The solar charge controller will need to charge the batteries at a set voltage, and the GT Inverter will hold the voltage lower so that it "skims" of any excess energy from the solar panels and sends them out to the Grid. The XW Hybrid Inverter acts, more or less, like a sophisticated "dump controller"... It is really the one controlling the battery bank voltage/state of charge (at least how I understand the XW system).

    Elsewhere, Solar Guppy recommended the XW battery setpoint voltage (I don't find it right at the moment). If these voltage points are set wrong, you will have "issues" with everything playing well together.

    Also, the BZ series of controllers (at least as of last year) are not known for being very good devices. You may have issues when trying to run them with your GT / Hybrid inverter confusing the BZ's.

    And watch what you do with the 60 volt solar panels... You probably cannot connect 2 of them in series without danger of overvoltaging your solar charge controller (most max out around 140-150 volts Voc--I do not know the BZ spec's).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • StevenB
    StevenB Solar Expert Posts: 71 ✭✭✭✭
    Re: 2 stage no float, Bulk-Absorb-Float

    Right, It's actually set up and running but I'm not sure of why things do what they do.
    It is a Hybrid system, storing in batteries, inverting to a sub panel (barn where my veggie freezers are) and selling to grid (windy days my meter goes backwards).

    I did advance the BZ's float turn pin, and yes the float light went off, and the amps going the batteries went up (according to my Pentametrix monitor).
    This is my quick reply just to clarify. I'll re-read and study this info. I wish I had found this forum 6 months ago....before I multiple confused myself!

    PS. The panels are in Parallel....and my next plan is to add 3 200w panels using the Xantrex Controller "xanbussed" to my Xantrex 6048 (I know names of things just stupid on the actual science!)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 2 stage no float, Bulk-Absorb-Float

    Steven,

    One way to help "unconfused" yourself is to pick the battery bank as the "heart" of your system.

    For the most part, the battery bank is what sets the "voltage" of they system and accepts/generates current as needed by the various sources and loads.

    The inverter "looks at the battery" and, based on the bank voltage (and its internal settings) decides how much power it can "skim" from the battery bank and ship out the GT interface and yet keep the battery charged.

    The Solar Charge Controller should have its Absorb Set Point set higher than the XW Inverter's set point. Basically, you want the solar charge controller to take 100% of the available energy from the solar panels and pump them into the "battery bank" (we know that the XW inverter is skimming this power off for GT use).

    If the GT inverter faults (turns off) for some reason, you still want the BZ controller to have some reasonable maximum voltage set point so that it will not overcharge your battery bank (prevents an inverter failure from causing your battery bank to overcharge).

    Do you have proper wire gauge, fuses/breakers, etc. between all of your major power components and know that the system is safe?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • StevenB
    StevenB Solar Expert Posts: 71 ✭✭✭✭
    Re: 2 stage no float, Bulk-Absorb-Float

    Last question first...I had a Master Electrician surfing buddy do all the wiring and with manufacture and dealers consulted. The biggest problem, is the damn thing worked right from the start.....leaving the fine parts to be solved and or understood.
    I worked with a Distributor who fortunately turned out to have both knowledge and integrity ..... to determine strategies, components, and costs. I also fabricated solar racks, turbine poles, battery barn, and dug conduit and Cat5 ditches (for XWconfig).

    Now all that's left is to understand what the heck is going on, and learn to manage it!

    Question: When you say "setpoint" for the Xantrex inverter....which XW Config setting would that be? Grid Sell Threshold?

    Thanks,
    Steven
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: 2 stage no float, Bulk-Absorb-Float

    On the XW system, if your intention is selling, you turn off the inverter charger and what ever excess the panels & wind generate go in to the grid. You don;t want sell and the internal charge both selected

    The BZ is the worst charger on the market ... not a good match for a 3K inverter-charger

    Under the sell option ( advance menu ) is the sell voltage ... set it to 52V , this keeps the battery's from being discharged and excess to the grid. Do not use the sell mode if you running the battery's down with loads at night... they need a full recharge before enabling the sell mode.
  • StevenB
    StevenB Solar Expert Posts: 71 ✭✭✭✭
    Re: 2 stage no float, Bulk-Absorb-Float

    Ayeee Yaeee Yaeee (BZ). Even though the BZ was gotten just to run this "test" model with the 2 panels...before I expand to more panels and the Xantrex Controller .......can you suggest a replacement? It will always just be for the two Kaneka 60's
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 2 stage no float, Bulk-Absorb-Float

    I believe that is correct (grid sell threshold).

    In this thread, Solar Guppy said that typical threshold voltage setting is around 52 volts (equal to ~13 volts on a 12 volt bank--which is a very low float voltage).

    Here is a long thread from a few years ago where the XW Hybrid GT Inverter was discussed quite a bit--Might help you understand some of the ins and outs.

    I am certainly not the expert here--If you post some of your set current set points for your inverter and charge controllers, perhaps Solar Guppy will drop by and offer some suggestions.

    -Bill

    PS: Never mind--I see Solar Guppy posted while I was looking around.

    -BB
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset