Why are my batteries absorbing and floating at a temperature much lower than what is set?

mevenablemevenable Posts: 54Registered Users ✭✭
I have two strings of 12 volt NC106 batteries, and have them set to absorb at 57.6 V and float at 54.4.  They absorb at 56, with a temperature corrected voltage of 56.8 according to the mate.  The battery temperature is generally about 31-33 C when they are absorbing and floating, which to me comes out to be a temperature correction of about 1 V max.  They should be absorbing then at an uncorrected voltage of 56.6 or higher (when the temperature is lower).  Likewise they are floating at about 52.8 V, which also seems too low.  In the log files, there are two voltage columns,  I think the first is the temperature corrected one, and the second is that very rough (0.4 V increment) uncorrected reading that is shown on the Mate3.  There are never readings of more than 56.8 V during absorption and 53.6 for Flotation.  Any ideas?  The batteries have been in use about 3.5 months
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  • mevenablemevenable Posts: 54Registered Users ✭✭

    ps, I have tested them with a volt meter, the voltage is as it shows on the Mate3 (uncompensated)


  • Raj174Raj174 Posts: 635Solar Expert ✭✭✭✭
    edited March 18 #3
    @mevenable
    I would check the "Battery Voltage Calibrate" setting in the FM80 and Radian 8048A to make sure they are adjusted to match the FNDC and actual battery voltage.

    Rick 
    3600W PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH LiFePO4 no BMS, 4500W genset.
  • westbranchwestbranch Posts: 5,087Solar Expert ✭✭✭✭
    I don't understand either your question in reference to the data you have stated for V and Temp and Correction value...?? Please clarify... 
    re your question, things do not happen that way, the CC will charge when it has power to send to the battery, the TC (Temp Compensation value ) only adjusts the charge Voltage  Upwards or Lowers it, it does not stop charging...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • EstragonEstragon Posts: 2,633Registered Users ✭✭✭✭
    A couple other things I'd check are the voltages at the FM and 8048 output terminals, and maybe double check that the absorb/float voltage settings are the same for both. IIRC, each has separate settings and they needn't be set the same.
    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
  • mevenablemevenable Posts: 54Registered Users ✭✭
    Hmmm.  Westbranch - I have a temperature sensor so everything automatically adjusts for temperature difference from 25C.  So, there is an unadjausted voltage and an adjusted voltage, and the temperature adjusted voltage should match the voltage at which the system is set to absorb and float.  I think.  But, in reality, it is about 0.8 V below, i.e. the battery is absorbing at a voltage below what it is set to absorb at, ditto float, even taking temperature into account.  The charge controller throttles back the current to keep it at the prescribed voltage, and when it gets down to 3 amps for a 200 amp battery bank it switches to flotation.  So, anyhow, if the voltage it is achieving it too low, seems like this could be an issue, and I was wondering why.  I thought of the calibration settings, there is one on the 8048, but the battery voltage calibration seems to be intended for adjustment if the measured battery voltage does not match what is on the mate3 (non-temperature adjusted V should be same as measured) .  On the FM, there are some limits for battery voltage but since I have temperature compensation set to "wide" they don't apply, and I don't see anything else.   I do not have a flexnet, they tried to install one at my request but could never manage to install it, it kept blowing out the hub for some reason.  Thanks guys,
  • westbranchwestbranch Posts: 5,087Solar Expert ✭✭✭✭
    Is there any other setting on the TC than 'wide'?
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Raj174Raj174 Posts: 635Solar Expert ✭✭✭✭
    @mevenable
    If you don't have a FNDC then you really need to make sure the FM 80 is calibrated to the true battery voltage. Check it in OpticsRe under Devices> FM80> Misc tab> Battery Voltage Calibrate. Sounds like the current setting may be .8 volts high. 

    Rick
    3600W PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH LiFePO4 no BMS, 4500W genset.
  • Dave AngeliniDave Angelini Posts: 3,900Solar Expert ✭✭✭✭
    post # 7 answer to RICKS question?. This is winter in most places, where are you? The temp comp voltage should be higher than programmed voltage in most places this time of year.

    Is the equipment new? There have been alot of issues of late with Different age outback equipment and compatibility to operate normally.

    Please list all of the equipment. Since you did not install this, why are you not talking with the installer? Answers here are only as good as the info you provide.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • just startingjust starting Posts: 221Registered Users ✭✭
    87f-92f battery temp would be a lower charge than if batteries were 35f voltage goes up as temp goes down- voltage goes down as temp goes up. With a battery temp sensor hooked up working properly
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
  • just startingjust starting Posts: 221Registered Users ✭✭
    So a .42 mv per 1c is about right at 2v and depending on conditions of connection a 1 volt drop seems reasonable.
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
  • mevenablemevenable Posts: 54Registered Users ✭✭

    they list 30 mv per 1C per battery in series , 30*4 batteries * 8C =960/1000 = 1 V

    meanwhile, it is central America dry season hottest time of year

    the installer does not seem to understand the issue, and Outback never will answer the question, I have been asking them for quite a while, they skip that one.


  • Dave AngeliniDave Angelini Posts: 3,900Solar Expert ✭✭✭✭
    OK, I use to live in Panama, Costa Rico and Guatemala. 
    so your absorb is 1.6V low from programmed value. This is measured with a decent DC voltmeter right?
    You probably do not have optics RE right?
    I do not know your battery but assume it is an AGM?

    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • just startingjust starting Posts: 221Registered Users ✭✭
    Ok I think I have this it's 30mv per degree centigrade per cell, so a 6v battery has 3 cells a 12 v has 6 cells and so on
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
  • just startingjust starting Posts: 221Registered Users ✭✭
    Ok just read the manual it's 5mv per cell per 1c
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
  • BB.BB. Posts: 27,699Super Moderators admin
    Measure the voltage for your car battery (around 12.7 volts stopped, 13.8 to 14.2 volts running, etc.).

    I have seen multiple dmm with weak batteries (or broken) that give readings like this (and consistent over days) but absolutely wrong readings.

    Bill "trust but verify" B
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • just startingjust starting Posts: 221Registered Users ✭✭
    How big of wire goes between the cc and battery bank, as a lot have said I'd check with a good multi meter and I would also re toque all of the connections considered it's a new system.
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
  • mevenablemevenable Posts: 54Registered Users ✭✭

    checked voltage with 2 independent volt meters.  I will try that


  • mevenablemevenable Posts: 54Registered Users ✭✭
    ok, I am onto something I think!  The misc menu on the charge controller gives a target voltage that is simply a temperature compensated version of the set voltage - for example, in the morning when it is not too hot it says it is aiming to absorb at 57.2, or 0.4 C below the 57.6 setting, due to the temperature correction.  As the day heats up, it changes to 57.2, or a temperature correction of 0.8 C, all as it should be.  Meanwhile, the Inverter shows a temperature corrected voltage that is equal to the already temperature corrected target voltage, and an uncorrected voltage that is even lower still.  In short, somehow the system is double dipping, the inverter and the charge controller are both correcting for temperature. I have to figure out how this is happening and correct it, have not yet worked it out.  Any thoughts, guys? 
  • just startingjust starting Posts: 221Registered Users ✭✭
    Are they both out back? I have a xantrex cc and a magnum inverter they both read different if there out back I believe you should only have one temp sensor and link all devices with a patch cable
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
  • mevenablemevenable Posts: 54Registered Users ✭✭
    that is the case, they are Outback, there is one temperature sensor, and they are all connected through a hub.  Nonetheless, somehow the correction is being doubled
  • just startingjust starting Posts: 221Registered Users ✭✭
    Saw your other post is this solved also?
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
  • mevenablemevenable Posts: 54Registered Users ✭✭

    Thanks for asking.  Yes, largely . . . slowly, slowly, I work my way up the learning curve.  I did post recently on my other topic.  I now DO understand even my original query about pv<load during the day.  bottom line on that was that a minor deficit is no problem, but I had to be sure my battery bank was big enough that if the sun went behind a cloud and most of the load hit the batteries it would not overwhelm them.  I am, gradually, getting reasonably comfortable, but there is a LOT of things that really don't have consistent answers.  Sometimes there are just too many variables, and often different manuals or different people have different ideas. 

    For example, the Outback Mate3 manual tells us that (with some load, presumably modest) the red battery status light comes on when the batteries are below 60% or 45.6 V.  The energy cell manual tells us that if the batteries recover to 48.8V after 24 hrs rest, that represents a 50% SOC.   From experience, I would say there is no way a battery that is in 45.6 V or less while in use will recover, ever, to 48.8V.  Only if the load was really large. 

    Meanwhile, also, the mate3 manual states that the green battery status light represents 80%+ SOC.   However, as far as I can tell, it is tied to the non-temperature compensated voltage, and it seems like when my batteries are fairly warm (31-34 C) I spend virtually no time at all in the evening before the batteries go to yellow (49.6) - within 10 minutes, generally.  I think this is just temperature related, that just as 60 is the new 50, so 49.6 is the new 50.4 V. 

    Anyhow it makes it hard to keep up with things, if I have the system set to go to grid at 48V, then if the night is hot that can happen way too soon, before I have used anything like the amp hours that I would have wished.  It is all a moving target.  I would have loved to have put in a FNDC, but they local company tried to install it twice, and both times the hub stopped working as a result, so we agreed to give up after replacing two hubs.  But, I really hope I am getting a bit closer to some version of reality.

    Another thing, I did an open circuit test of the batteries recently and the idea was to see if they were holding charge after 24 hours at rest.  However, according to the manual 50.4 V at the end of the game would mean the batteries are kaput, and 51.36 means they are great, but this is supposed to be temperature compensated and it is not clear whether that is the temperature at the start of the test or the end of the 24 hours. The average for each string was about 51.1 V, but the temperature at the beginning was about 34 C and at the end was about 29 C, either way it would make the corrected value a bit high.  Also, I have two volt meters and they give me totals about 0.2 V different one from the other.  The 51.1 V was on the lower one, the other would have the uncorrected value at 51.3 V, making corrected values even higher. The manual for them says they can have an error of +/- 1%. which at 50 V is +/-0.5V.  The individual batteries at the end of the test varied by 0.1 V on one string, and virtually nothing on the other string.  The two strings were the same though. Are the batteries on the one string that were lower a bit worse, and the ones that were better a bit better, or is it the total that counts?  They were similarly different at the beginning of the test.  It feels like getting lost in the details, but at the same time when the difference between dying batteries and healthy ones is just 1 V the details seem to matter. 

    Hope all this at least helps someone else who is feeling overwhelmed feel a bit less alone.

    cheers.

  • Raj174Raj174 Posts: 635Solar Expert ✭✭✭✭
    mevenable said:
    ok, I am onto something I think!  The misc menu on the charge controller gives a target voltage that is simply a temperature compensated version of the set voltage - for example, in the morning when it is not too hot it says it is aiming to absorb at 57.2, or 0.4 C below the 57.6 setting, due to the temperature correction.  As the day heats up, it changes to 57.2, or a temperature correction of 0.8 C, all as it should be.  Meanwhile, the Inverter shows a temperature corrected voltage that is equal to the already temperature corrected target voltage, and an uncorrected voltage that is even lower still.  In short, somehow the system is double dipping, the inverter and the charge controller are both correcting for temperature. I have to figure out how this is happening and correct it, have not yet worked it out.  Any thoughts, guys? 
    I don't see any temp comp info on the "misc" page. Below is the misc page of a FM60 on a system I manage with OpticsRe. Does yours look the same?

     
    3600W PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH LiFePO4 no BMS, 4500W genset.
  • mevenablemevenable Posts: 54Registered Users ✭✭
    same.  I am talking about the misc menu on the FM80 itself.  different.
  • EstragonEstragon Posts: 2,633Registered Users ✭✭✭✭
    One "variable" that seems to be causing some confusion is temp correction. Maybe some clarification will help simplify things.

    A battery charges and discharges through an electochemical process. The process is different for different chemistries, but in most (all?), the process happens faster at higher temps. Note it's a process *rate*, not a process *state* that's affected by temp.

    In other words, my understanding is you shouldn't adjust a static (resting) voltage for temp, as that's the static state of electrical potential. A fully charged 48v nominal FLA bank will be ~51v (+/- a tenth or two) whether it's 30°C or 0°C.

    You adjust charging voltages because the rate of the chemical reaction involved is higher at higher temps. Apparent capacity is reduced at lower temps because the reaction is happening more slowly, so a lower potential rate of discharge (power over time, not absolute amount of power) is available.

    Specific gravity needs to be temp compensated because density changes with temperaure (a physical condition, not chemical process).

    I mostly ignore the SOC indicator on my mate, as I don't think it's sophisticated enough to be useful to me. Maybe it can be made so, but I have other (IMHO better) ways of estimating SOC, so I've not bothered with the mate for SOC.
    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
  • mevenablemevenable Posts: 54Registered Users ✭✭
    This explanation makes all the sense in the world to me, thanks!!!!  My 51.1 V is "the final answer" then - and it might even be the 51.3 V I got with my other voltmeter.  I was confused by the Energy Cell Manual description for the 24 hours open circuit test, as follows:Remove all battery connections, then allow the battery to rest in this state for 24 hours. Test the battery voltage, compensating for temperature. The EnergyCell RE NC should measure 12.84 Vdc. The EnergyCell GH battery should measure 12.95 Vdc. A battery below 12.6 Vdc has lost capacity and may need to be replaced.
  • mevenablemevenable Posts: 54Registered Users ✭✭
    oh, sorry RAJ174 - too many things in my mind.  That IS the menu, I changed the Battery Voltage Calibrate to -0.5 V since there seemed to be some disagreement between measured values and what the CC had, this is supposedly more cosmetic than actual, but nonetheless, since then, my actual measured battery voltage plus correct temperature compensation for the current battery temperature are finally adding up to the correct total, 57.6 V for absorption and 54.4 V for flotation. If it was not related to that change, then it was a heck of a coincidence.  Not sure if that is what I should have done, or whether there is some underlying problem that is not being addressed
  • Raj174Raj174 Posts: 635Solar Expert ✭✭✭✭
    mevenable said:
    oh, sorry RAJ174 - too many things in my mind.  That IS the menu, I changed the Battery Voltage Calibrate to -0.5 V since there seemed to be some disagreement between measured values and what the CC had, this is supposedly more cosmetic than actual, but nonetheless, since then, my actual measured battery voltage plus correct temperature compensation for the current battery temperature are finally adding up to the correct total, 57.6 V for absorption and 54.4 V for flotation. If it was not related to that change, then it was a heck of a coincidence.  Not sure if that is what I should have done, or whether there is some underlying problem that is not being addressed
    I agree, seemed like the right adjustment. Glad it's working better.
    3600W PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH LiFePO4 no BMS, 4500W genset.
  • mevenablemevenable Posts: 54Registered Users ✭✭
    Estragon - further on the voltage issue - would it make sense for hot batteries to go below 50 V (yellow battery status light on Mate3) because the voltage that is being used is not temperature compensated (49.6 is the new 50.4?)  Seemed like they used to hold onto that green light status for almost a KWH of use, but now they go to yellow within 0.1-0.2 KWH.  One guy at outback said it was due to not being temperature controlled. 
  • EstragonEstragon Posts: 2,633Registered Users ✭✭✭✭
    I'm not sure I understand the question, or the OB response. A warm bank will have a higher apparent capacity than a cold one. All else held equal, I would expect a warm bank to voltage sag less than a cold one under a given load. That the status light indication is based on actual voltage seems right. *Target* voltages for charging get temp compensated. *Actual* voltage just gets adjusted for any offset between bank and device reading. The mate SOC indication should include this offset value (-0.5v?).

    Voltage sag will be a function of both power and time. A .2Kwh load over 1 minute will result in a much larger voltage sag than a .2Kwh load over an hour. I made toast this morning on a nominal 350ah 48v bank. The voltage sagged to a ~65% SOC while making the toast (~850w) and running some lights, etc, but rebounded in 10 or so minutes to around 80%, which is close to what actual SOC would be.

    Assuming your .2Kwh load was over a longish period of time (like an hour or two), a drop from 100% voltage indicated SOC to <80% seems a lot for a (IIRC) [email protected] bank. It may appear to be happening faster because of a change in battery-device offset?

    A 0.5v battery offset (calibrate) seems high to me. I think mine is 0.1. If you read voltage at device terminals and battery posts with the same meter, is there a roughly 1/2 volt difference?
    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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