State of charge

HotRodHotRod Registered Users Posts: 82 ✭✭
Hello all! I'm new here. Just joined today. I have just finished installing my system and I'm fumbling my way through most of it. What I have is:
2- XW+ 6848s
2- MPPT 80 600s
13.6kW array
1- 24-85-27 lead acid battery rated 90% and tested 1105AH

I do not have the battery temp sensor wired in. Is this why the ComBox won't show the S.O.C.?
2 Schneider XW+ 6848 inverters
2 Schneider MPPT 80 600 Charge Controllers
Combox
40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
1 big ass 24-85-27 refurbished forklift battery w/1430AH
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Comments

  • BB.BB. Super Moderators, Administrators Posts: 31,613 admin
    My questions would be... Is the XW and Combox system properly configured (battery specifications)? Also, it is possible that the Combox may not show SoC until the battery bank is fully charged (~59 volts for 2-6 hours absorb charging). Generally, the "full charge" is what resets the SoC calculations to 100% (I know nothing about XW and combox systems).

    By the way, is your battery a 1x 48 volt flooded cell lead acid battery or a 2x 24 volt batteries in series for 48 volt bus?

    And--Do you have a hydrometer and digital multimeter to do manual state of charge measurements? You need to make sure your battery bank is properly and fully charged until you get the system setup and running. You don't want to let the batteries get damaged while you are working out the issues.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Solar Expert Posts: 5,563 ✭✭✭✭✭
    edited May 2019 #3
    Have you setup the Commbox?

    http://www.xantrex.com/documents/Accessories/Combox/975-0704-01-01_RevA(Vendor).pdf

    Your battery is a 24-85-27, this means it originally had;

    24 -2.1 volt cells, making it a 48 volt nominal battery

    Each positive plate holds up to 85 amps at a 6 hour discharge rate, but normally batteries in solar energy systems are rated at a 20 hour rate. So at a 20 hour rate this would be more roughly 110 amps.

    The battery has 27 plates 13 of which are positive plates or 13 x 85 = 1105 at a 6 hr discharge rate or 13 x 110 = 1430 at a 20 hour discharge rate.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    Photowhit, thank you for the info. I had battery capacity set at 1105. I'll change it to 1430.

    BB, we started a few days ago with a full charge and got off the grid, other than the few times I've turned it on here and there. Typical day has looked like this
    It's been cloudy everyday since we started. But we get to float voltage everyday and maintain it for a few hours before we lose the sun. Today has been great though. I've only had a couple dips off full charge. Am I hurting my battery doing this?
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    edited May 2019 #5
    BB, I forgot to mention that I do have a hydrometer, well, a refractometer is what I use. It was showing 1.29 after 4 hours rest the day we went off the grid. I haven't checked any cells since then. Today is our 7th day off grid.
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    Today's charge cycle
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    I just went and checked my SG in the battery. It was testing 1.31 in every cell. Whats up with that? i thought 1.29 was 100% SOC?
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • mcgivormcgivor Solar Expert Posts: 3,790 ✭✭✭✭✭✭
    Do you have a battery monitor connected in the system? This will provide more accurate state of charge information, the battery  temperature sensors have no effect on state of charge information but should be connected to prevent over/under charging.
    https://www.solar-electric.com/schneider-electric-conext-battery-monitor.html
    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.
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    I do not have the battery monitor. I didn't think I would need it with the ComBox. I assumed it would do it all. I don't know why I expected it to know what was going on with the battery. So I need the monitor to get a SOC reading? Ok.
    Now to the temp sensor. I have a refurbished forklift battery. Where should I put the sensor? Readings with an IR thermometer show the top of the battery to get the hottest. The 3/8" steel box the individual cells are in seems to stay about 10 degrees cooler than the tops. What do you suggest? Also, I have read that the temp sensor cable can't be shortened, can it be lengthened? I have a long run from the charge controllers to the battery.
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • mcgivormcgivor Solar Expert Posts: 3,790 ✭✭✭✭✭✭
    The battery monitor provides a wealth of information, features above and beyond what the XW can provide, some of which may be superfluous. Depending on needs or wants would determine it's value, there are YouTube videos which explain it's features, operating without one is possible but the monitor calculates what current goes into and out of the battery to determine it's information.

    Temperature sensors are usually placed about half way down a cell in the middle of the bank, with a forklift battery this may not be possible, an alternative would be a battery terminal covered with some insulation material to minimize the influence of possible cooler ambient air flow.

    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.
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    So how about this, place the temp sensor on one of the bus bars connecting the batteries and insulate it with some closed cell foam. Lead is a pretty good thermal conductor so I'm gonna assume, if insulated, the bus bars will be close to the same temp as the plates inside the battery. 

    Now, back to the sensor cable. Can it be safely lengthened or will that have the same detrimental effect as shortening it?
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • Ralph DayRalph Day Solar Expert Posts: 940 ✭✭✭✭
    Do you calibrate your refractometer before use?  I keep a baby food jar of distilled water on top of the batteries so the temperatures are the same, or almost.  A digital probe thermometer (available at fancy kitchen ware stores) to check the temp is the same as the electrolyte is necessary.  Water first, adjust the calibration to the water line...then the temperature compenstation is done.  Acid sample next.  If the refractometer is not calibrated you're just shooting in the dark for actual SG reading (btdt).

    If the water temp is different from the acid I pop it in the freezer or fridge for a minute when it's warmer, and test.  If colder, hold the jar between your hands to warm it up a bit.  I actually touched it to my woodstove earlier this week, a few seconds and it brought the temp up a few tenths of a degree as needed.  But calibration is necessary for temperatuere compensation.

    Ralph
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    Thank you Ralph. I did not take temp into account when reading the SG. I measured 76-78°F on the outside of the steel container the batteries are in. The battery tops were pretty consistent at 85°F. I did not take direct measurements of the fluid temp.
    Thanks again. This info will be built into my spread sheet and maintenance procedures.
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • littleharbor2littleharbor2 Solar Expert Posts: 1,598 ✭✭✭✭
    How long of a run from CC to battery? You need to keep voltage drop to a minimum here. Recommend using the largest wire your CC will accept.

    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, 540 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • HotRodHotRod Registered Users Posts: 82 ✭✭
    edited May 2019 #15
    Littleharbor2, about 12 feet of #4AWG from each CC to the PDP with a safety switch in the circuit. From there it's 25 feet of 4/0AWG to the battery.

    Edit: that #4AWG is actually right at 20', not 12
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    If my inverter can display this battery SOC, why can't the ComBox do the same?
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • mcgivormcgivor Solar Expert Posts: 3,790 ✭✭✭✭✭✭
    HotRod said:
    So how about this, place the temp sensor on one of the bus bars connecting the batteries and insulate it with some closed cell foam. Lead is a pretty good thermal conductor so I'm gonna assume, if insulated, the bus bars will be close to the same temp as the plates inside the battery. 

    Now, back to the sensor cable. Can it be safely lengthened or will that have the same detrimental effect as shortening it?
    Being that the temperature sensor wires carry little to no current  it probably wouldn't make much difference in the actual readings, even sensors have a tollerance range + or - 0.5% for example. My BMS has two temperature sensors that read ~0.5°C difference even when interchanged, the difference migrates to the particular sensor, both with equal wire length. 
    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.
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    edited May 2019 #18
    So adding a female by female coupling and another 15' of cable shouldn't throw off the temp readings by enough to matter. Cool, ty.

    And the temp sensor placement? Do you think that would work well?
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    This forum has been great. I want to not only thank the folks commenting here, but everybody on this site who have posted to ask and answer questions. Huge wealth of information in here. I've learned enough since yesterday to get my settings to what I feel is correct. We are now operating online (grid interactive) with sell disabled. It's working beautifully thanks to you guys. Can't wait to see it in action after we get our reversing meter. 
    Can anybody tell me if I'm hurting the battery with those dips in the charge cycle and the slow run up in the mornings? 
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • mcgivormcgivor Solar Expert Posts: 3,790 ✭✭✭✭✭✭
    Dips in voltage along with state of charge based on voltage is normal, it's reactionary, not a true indicator, batteries in general are resilient, able to withstand enormous amounts of current for short durations, it's the rebound voltage which is important.

    A large load, for example a motor, may demand 10× the current on startup, this will result in voltage sag momentarily, for this reason it's common to program a hysteresis factor to ignore such events preventing inverter shutdown for a given period of time. This may reflect in the battery capacity appearing low on a graphical level responding to voltage, but it's a false indicator for the most part. This is where the battery monitor comes into play, should the need be required, it's not really necessary if a sound understanding of how a battery responds to large loads, but will give peace of mind. 
    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.
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    Ok, that sounds logical to me. I have a limited understanding of hysteresis.
    What I'm more concerned with are large and prolonged absences in direct sunlight accompanied by a pull on the battery. This is soon followed by a return to absorbtion charging. Is this hard on it?

    Here is the battery bank summaryso far today
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    Here is the PV & AC daily summary
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    Is there a way to change the colors on the graphs coming from the ComBox? PV Total Power and Load Power are practically the same color.
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    Is this erratic charging harming the battery?
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    Am I too far off the topic of the original post? Do I need to start a new thread to get answers? Is the question I'm posing too difficult to answer so I'm just going to be told to do the research and tailor a plan for my specific needs? I take direction well. Just looking for general advice.😃
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • mcgivormcgivor Solar Expert Posts: 3,790 ✭✭✭✭✭✭
    There is quite a bit of data in the screen shots, post 17 shows what would appear to be float occurring at noon, it also seems there are some high loads for short durations, these will sag the voltage creating what would appear to be erratic charging, in reality it's normal. Adjusting settings to prioritize battery charging with solar, using grid to support loads during this period will reduce the peaks and valleys, realistically it' comes down to personal preferences, what it is you hope to achieve.

    Being a grid interactive system, perhaps it would be best to start a new thread, dealing with specifics relevant to how you wish to utilize the battery in conjunction with the grid, such as grid support, load shaving and so forth. 

    Creating a signature in your personal settings will assist others in knowing what equipment you have, without referring to the original post, which may/will become obsolete in a very short period of time.

    Don't worry too much about what the graphics show, lead acid batteries are extremely resilient, if the charge controller settings are correct and they reach float at some point in the day they are probably fine, reassuring yourself with SG readings, the gold standard, should put your mind at ease. Yeah it seems overwhelming at first, it really takes about a year to fine tune, dealing with specifics in a pragmatical way will make the picture appear clearer.


    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.
  • BB.BB. Super Moderators, Administrators Posts: 31,613 admin
    You are doing fine with your posts. And I would suggest you keep all of your Q&A in this same thread so we can follow the discussion.

    If you have a completely different question later (new well pump, installing a second system in a cabin, etc.), then I would suggest a new thread.

    I do not have your system and I am not off grid / battery based system myself--So I cannot really add much to what is being discussed... Other than to monitor your Specific Gravity (typically you pick one cell that has "low SG", and monitor that daily/weekly. And monitor (log) all of your cells once a month. And use a DMM to measure the voltage of each battery (or cell) in your string (and log).

    You are usually looking for 2 major "things"... And differences between batteries (one battery/cell with high or low SG, high or low voltage, etc.). Take voltage readings at different times of the (during charging, during night time loading, etc.). As long as all the readings are close to the same, all is (usually) well. And you typically want to look for min/max too... Very low SG and/or voltages (low charging voltage, low load voltages, etc.) are things you need to figure out. Is there a problem (charging voltage not set correctly, bad wiring connection back to solar array, too much loads and not enough sun, etc.)... You have a living/breathing "thing" here... And you need to see what "healthy" is, and when something is "not right" (need further debugging).

    What you are seeing--The changes in battery bus voltage and such during the day is normal. And does not hurt your batteries (other than adding cycles--Which is one of the wear factors that limit battery life).

    We are all volunteers here.. So sometimes answers may not come for several days--And, sometimes, we just do not have answers (time to call for support).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    edited May 2019 #28
    Sorry, I'm a little antsy. I've literally been running for 7 days and I'm realizing how much research I didn't do about the batteries. Dips and sags in voltage were expected. I just hadn't considered how it would affect the battery. I've done a lot of reading too and it would seem heat plays the biggest factor in longevity. I'm not stating that it's the only factor, just a big one. Right up there with cycles. I'm learning. There is a huge wealth of information on this website.  I can't thank you guys enough for not only the answers you've given here but elsewhere. You guys are all over this forum. Thank you for sharing. I'm gonna take mcgivers advice and start a new thread outlining my goals. I'll add my equipment to a signature and my new thread will focus on tuning the equipment. It seems to be a common problem. Not because the equipment is too complex. I see it ass extremely flexible. Able to conform to just about any configuration a person desires and we all want something slightly different. Thanks again.
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    I can't figure out how to add a signature or change my avatar. I bet if I search the form there's a thread that tells me how. 😁
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
  • mcgivormcgivor Solar Expert Posts: 3,790 ✭✭✭✭✭✭
    HotRod said:
    I can't figure out how to add a signature or change my avatar. I bet if I search the form there's a thread that tells me how. 😁

    Click your avatar to get to your page, on the left of the avatar there is a man in a box click that to edit profile, it's pretty self explanatory from there on.

    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.
  • HotRodHotRod Registered Users Posts: 82 ✭✭
    Thanks mcgiver. I did exactly that and this is what I'm offered when I try to edit my profile.
    2 Schneider XW+ 6848 inverters
    2 Schneider MPPT 80 600 Charge Controllers
    Combox
    40 335w Canadian Solar panels, 13.4kW array on an Iron Ridge racking system
    1 big ass 24-85-27 refurbished forklift battery w/1430AH
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