Float or higher charge voltage for value regulated sealed lead battery

Fabian
Fabian Registered Users Posts: 131 ✭✭
I am using a 24v system and I have (4) EnerSys PowerSafe 12V190F 180Ah valve regulated sealed lead acid battery which I connect in series and parallel so my battery bank is 24v at 380Ah. I am trying to figure out what is the correct max charge voltage it is suppose to get. The specs on each of the batteries says max float charge voltage per cell is 2.29v which works out to be 13.74v per battery and when you double for 24v that works out to be 27.48v.

So should I set the max charge voltage to be always 27.48v on my charge controller?
What if I run down the battery to 23.3v or slightly below 24v sometimes should it still charge up to 27.48v or do I need to go a bit higher sometimes because of the lower discharge?

Does this battery bank require equalization charge sometimes and if yes how often should it be applied and what is the max charge voltage I should use for equalization charge and how long should it remain on equalization charge?
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Comments

  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,039 ✭✭✭✭✭
    edited July 2017 #2
    Many of the AGM batteries out there are designed for UPS/float service. They aren't made for daily cycle service. This may be why you aren't seeing a bulk charge voltage on the label. A lot of people get decent performance with these batteries in part time systems where say in a cabin or RV you don't cycle them on a regular basis.

     Typically AGM batteries don't want as high a charging voltage as a flooded  battery wants because they have to recombine the hydrogen gasses back into the electrolyte. If charged at too high a voltage they cant recombine the gas fast enough and will vent and lose electrolyte which cannot be replaced. They all vary in bulk/absorb voltage allowances but usually about 14.4 to 14.6 is safe per 12 volt battery. Gel batteries are even worse as the gas bubbles will become trapped in the gel electrolyte so they will max out at about 14.2 volts max.
     
    Generally speaking sealed batteries shouldn't get equalized for the aforementioned reasons. Some Mfg. will call for a periodic slightly higher voltage, "Freshening charge".

    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,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    From what I can gather these batteries are designed for telecomm or UPS service, not for cyclical use, the float voltage is not the charge voltage, on a 24V nominal system the bulk/ absorb voltage would be in the neighborhood of 28.8V, float would be around 27V, as far as equalization is concerned, they should not be equalized, unless the manufacturer recommends to do so.  If you are experiencing low voltage on discharge it is more than likely because they are not being fully charged, just a speculation as I've no idea of the loads, 
    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.
  • Fabian
    Fabian Registered Users Posts: 131 ✭✭
    My charge controller does not allows you to set bulk/absorb then set float voltage.  It just allows you to set the pv cut off voltage and whatever voltage you set it at that's where the charge voltage doesn't pass. It will remain at that voltage sending high current into the battery until the current drops down to a small amount and will start to float at that same voltage. So in my case If i set it at the 27.4v will the battery get a full charge? Also what would be the float current going into the battery that would suggest my battery bank is fully charged? My bank is 380Ah so what current or percentage of the 380Ah going into the battery at 27.4v would suggest it is fully charged?
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    The bank will eventually charge at float voltage, but off-grid we don't generally have time for that (sun goes down, etc.). I consider between 1-2% of capacity at absorb voltage to be fully charged, at which point the controllers go to float voltage.

    Personally, I wouldn't buy or use a controller that didn't have separate absorb and float voltage settings for off-grid use. Such a controller might be okay for a standby application, but not for regular daily cycling.
    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
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,039 ✭✭✭✭✭
    Raise your setting to 28.8. This will get you closer to full charge. When your controller transitions to float and batteries drop their surface charge voltage, like hours after dark with no load, you should see what your float voltage is.

    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,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • Solray
    Solray Registered Users Posts: 246 ✭✭✭
    You cannot get 380 ah out of any configuration using a 180 ah battery. You are limited to numbers that are divisible by 180. ie. 180, 360, 540, 720, etc.
  • Horsefly
    Horsefly Registered Users Posts: 470 ✭✭✭✭
    Solray said:
    You cannot get 380 ah out of any configuration using a 180 ah battery. You are limited to numbers that are divisible by 180. ie. 180, 360, 540, 720, etc.
    It was a typo. The batteries the OP mentioned are 190AH.
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 8S (25.6V), 230Ah Eve LiFePO4 battery in a custom insulated and heated case.
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    > @Solray said:
    > You cannot get 380 ah out of any configuration using a 180 ah battery. You are limited to numbers that are divisible by 180. ie. 180, 360, 540, 720, etc.

    I'm guessing it's a simple arithmetic error or typo in the OP, but strictly speaking you could get 380ah from a 180ah battery. Just have to warm it up some.
    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
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭

    Fabian said:
    My charge controller does not allows you to set bulk/absorb then set float voltage.  It just allows you to set the pv cut off voltage and whatever voltage you set it at that's where the charge voltage doesn't pass. It will remain at that voltage sending high current into the battery until the current drops down to a small
    amount and will start to float at that same voltage. So in my case If i set it at the 27.4v will the battery get a full charge? Also what would be the float current going into the battery that would suggest my battery bank is fully charged? My bank is 380Ah so what current or percentage of the 380Ah going into the battery at 27.4v would suggest it is fully charged?

    A setting of 27.4V is unlikely to get the battery fully charged in an off grid cyclical application, this low setting intended for standby use, UPS/telecom, which  relies on the fact that grid power is available 24 hours, the next discharge may be days,weeks or months  away, thus allowing a full charge overy time. Discharging  on a daily basis, coupled with a limited window of opportunity, sunlight, may lead to problems related to insufficient charging, the amount of discharge, load, is a critical factor, not mentioned, but if the load is light and the voltage drops below 24V, the capacity is ~50% or less. A voltage in the range of 28.2 to 28.8V @25°C, would seem more appropriate. Could you show your controller and list the loads including PV array  size, this would help everyone determine what exactly it is you are dealing with.  
      
    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.
  • Solray
    Solray Registered Users Posts: 246 ✭✭✭
    190 ah will get you a 380ah bank wired correctly. There are ways of getting odd ah ratings from a bank, but many of them are unsafe and can cause a fire so they are not recommended. :)
  • Fabian
    Fabian Registered Users Posts: 131 ✭✭
    it was typo. I didn't even realize until now. I meant 360ah of course. So basically if I set my controller to 28.8v is it safe to float charge my value regulated battery at that voltage once the battery temp is @25°C or below?
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    Because there are only so many hours of useful sunlight the current would taper down to almost nothing, probably in a pulse width modulation, at the higher voltage, there would be no float perse, the voltage would drop as the sun sets until it settles, usually  around  25.4V, without load. 
    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.
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,039 ✭✭✭✭✭
    As mentioned, that setting is the bulk/absorb voltage., Not float voltage.

    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,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Read this document abut AGM charging... http://www.cdtechno.com/pdf/ref/41_2128_0212.pdf  lots of good info , just have to reread it as it is up to you based on usage and temps and make...

     I use 28.8 in summer and 28.9 in winter...

     
    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
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,039 ✭✭✭✭✭
    edited July 2017 #16

    Here's some info I pulled from a seller on ebay for your brand of controller. It should be self explanatory as to the charging  parameters. You have different voltages for different types of batteries and also user settable voltages from 9 - 17 volts.







    Model

    Tracer1210A

    Tracer2210A

    Tracer3210A

    Tracer4210A

     

     

     

     

     

    Nominal system voltage

    12/24VDC auto work

    Rated charge current

    10A

    20A

    30A

    40A

    Rated discharge current

    10A

    20A

    30A

    40A

    Battery input voltage

    8~32V

    Max. PV   /   open circuit  voltage

    100V(at minimum operating environment temperature)          92V(at 25℃ environment temperature)

     MPP voltage range

    VBAT+2V~ 72V

    Max. PV input power

    130W(12V) 260W(24V)

    260W(12V) 520W(24V)

    390W(12V) 780W(24V)

    520W(12V) 1040W(24V)

     Equalize charging voltage

    Sealed: 14.6V, Flooded: 14.8V

     Boost charging voltage

                                  Gel: 14.2V, Sealed: 14.6V, Flooded: 14.8V

      Float charging voltage

    13.8V

     Low voltage reconnect voltage

    12.6V

     Low voltage disconnect voltage

    11.1V

    Self-consumption

    ≤20mA/12V; ≤16mA/24V

    Temperature compensation coefficient

    -3mV/ ºC/2V(25 ºC)

    Working temperature

    -25 ºC ~+45 ºC

    Enclosure

    IP30

    Overall dimension

        172x139x44mm

    220x154x52mm

    228x164x55mm

    252x180x63mm

    Power terminals

    12AWG(4mm2)

    6AWG(16mm2)

    6AWG(16mm2)

    6AWG(16mm2)

    Net weight

    0.6kg

    1.1kg

    1.2kg

    1.9kg

    Battery Voltage Parameters (parameters is in 12V system at 25 °C, please use double value in 24V.)Battery charging setting

    Sealed

    Gel

    Flooded

    User

    Over Voltage Disconnect Voltage

    16.0V

    16.0V

    16.0V

    9~17V

    Charging Limit Voltage

    15.0V

    15.0V

    15.0V

    9~17V

    Over Voltage Reconnect Voltage

    15.0V

    15.0V

    15.0V

    9~17V

    Equalize Charging Voltage

    14.6V

    ——

    14.8V

    9~17V

    Boost Charging Voltage

    14.4V

    14.2V

    14.6V

    9~17V

    Float Charging Voltage

    13.8V

    13.8V

    13.8V

    9~17V

    Boost Reconnect Charging Voltage

    13.2V

    13.2V

    13.2V

    9~17V

    Low Voltage Reconnect Voltage

    12.6V

    12.6V

    12.6V

    9~17V

    Under Voltage Warning Reconnect Voltage

    12.2V

    12.2V

    12.2V

    9~17V

    Under Volt. Warning Volt.

    12.0V

    12.0V

    12.0V

    9~17V

    Low Volt. Disconnect Volt.

    11.1V

    11.1V

    11.1V

    9~17V

    Discharging Limit Voltage

    10.6V

    10.6V

    10.6V

    9~17V

    Equalize Duration (min.)

    120

    ——

    120

    0~180

    Boost Duration (min.)

    120

    120

    120

    10~180

     

                                           


    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,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • bsolar
    bsolar Solar Expert Posts: 103 ✭✭✭
    edited July 2017 #17
    Fabian said:
    it was typo. I didn't even realize until now. I meant 360ah of course. So basically if I set my controller to 28.8v is it safe to float charge my value regulated battery at that voltage once the battery temp is @25°C or below?
    it will be safe but it wont hurt to lower the value and thats what i would do since it sounds like your controller is a diverter or cutoff type .. i would shoot for a value of 13.4v or even 13.2v per battery, you will lose very little in usable capacity and they will last longer ... to equalize simply add a volt ( per battery) .. only other contingency would be if you have a giant array and no real way to regulate amps, in that case buy a better controller, you could afford the panels so get a 3 stage controller/s ...
  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    You can set "Charging Limit Voltage" to 14.4V and "Float" to 13.2V.   Adjust as needed for batteries in series.

    I am available for custom hardware/firmware development

  • Fabian
    Fabian Registered Users Posts: 131 ✭✭
    still waiting on an answer someone please.
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,039 ✭✭✭✭✭
    Fabian said:
    still waiting on an answer someone please.
      Fabian,
      You would have better luck getting an answer if you started a new thread instead of jumping into someone else's thread. Also your question is impossible to answer because there is no way to judge appropriateness of a charge controller  without more information.
     The way it usually works is you need to know your load over the course of a 24 hour period as well as peak load. Then you figure out an appropriate size battery. Battery size and load dictates charging requirements. Peak load will determine inverter size, if using an inverter.  From there you figure how much solar and what size charge controller you need.


    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,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • Fabian
    Fabian Registered Users Posts: 131 ✭✭
    Charging my current battery bank with my regular PWM charge controller how long should I let the battery bank stay at the bulk/ absorb voltage of 28.8v before I cut it down to 27v for float charge?
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    Many(most/all?) PWM controllers will terminate absorb when the duty cycle (number/length of pulses over a given time period) falls to a predetermined level. The manual should have details.

    With no other loads, 3 hours or so of absorb would be typical.
    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
  • Fabian
    Fabian Registered Users Posts: 131 ✭✭
    Regular(most) pwm controllers will terminate the Pv cutoff voltage that you set for eg.28.8v and then switch to a lower voltage setting automatically for eg.27.4v and then commence float charging at that lower voltage or will still maintain the high voltage setting that you set but then switch to a lower current charging?

    My controller just has one setting in which i set the cutoff voltage and whenever it reaches that voltage setting it remains at that voltage setting and then the current decrease gradually as the battery starts to get closer to the full charge level so in my case the controller won't decrease the high voltage setting once the battery gets full charge and then switch to a float charge voltage for eg. 27.4v. It just has one cutoff setting which it floats at that same setting.
    Is there a way for me to let the controller automatically switch from that high bulk charge/absorb voltage after a certain length of time and then switch to a lower voltage setting to float charge with?
    Or suppose i use a temp sensor (BTS) which attaches to the battery bank will the regular pwm controller ignore the voltage setting that i set and auto adjust the voltage/current once the battery starts to get too warm or too hot or pass the safe temp range?

  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    It's normal for current to drop off as the battery gets full at absorb voltage. It's not a matter of the controller reducing the current, it's just that the battery takes less current at a given voltage as it gets full.

    There definitely should be some way to get the controller to go to a lower float voltage when (if) the battery gets close to full.

    A couple of things come to mind:

    1. It may be that the controller doesn't know the battery is full. For example, you may have loads besides charging which prevent the duty cycle from dropping low enough for long enough for the controller to know to go to float.
    2. There may be a duty cycle setting that is set too low, or a time at that duty cycle setting that's too long.

    A temperature sensor should adjust voltage. It will lower voltage for higher temps, and vice versa. I don't know that it's directly related to the transition to float issue, but generally a good idea anyway.
    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
  • Fabian
    Fabian Registered Users Posts: 131 ✭✭
    If i install a BTS between my current VRLA battery bank which are factory default to float at 27.4v and set my one setting controller to cut the bulk charge at 28.8v which it will begin to float at that same voltage, will the BTS prevent the battery from getting too warm or pass the safe temp range by reducing the current or the voltage or both to a very minimal amount that will prevent the battery from gassing too  much and prevent water loss or go into thermal runnaway at that 28.8v setting?

    My controller has a Temp compensation of 4mV/Cell/'C does that indicate that once a certain battery temp is reach, the controller will decrease the charging voltage according to the temp reading and it will even reduce it more if the temp increase again? 
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    Yes, the controller should reduce voltage as temp rises on the RTS. IIRC the compensation is typically from 25°C. Current is affected only indirectly, as the battery will accept less current when voltage is reduced.

    If ambient temps are significantly different than battery temps, you may want to cover the sensor part that sticks onto the battery with a bit of insulation.
    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
  • fratermus
    fratermus Registered Users Posts: 48 ✭✭
    Estragon said:
    Personally, I wouldn't buy or use a controller that didn't have separate absorb and float voltage settings for off-grid use. Such a controller might be okay for a standby application, but not for regular daily cycling.

    Dunno.   If I were cycling each day and had one setpoint I'd consider setting it to Vabs.  And watering regularly.  :-)
  • Fabian
    Fabian Registered Users Posts: 131 ✭✭

    Dunno.   If I were cycling each day and had one setpoint I'd consider setting it to Vabs.  And watering regularly.  :-)
    what is Vabs?
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,039 ✭✭✭✭✭
    The point at which your controller transitions from Bulk to Absorb . While in absorb mode the voltage is held at that setpoint until the battery is done absorbing current. from there the controller transitions to float mode.

    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,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    fratermus said:
    Estragon said:
    Personally, I wouldn't buy or use a controller that didn't have separate absorb and float voltage settings for off-grid use. Such a controller might be okay for a standby application, but not for regular daily cycling.

    Dunno.   If I were cycling each day and had one setpoint I'd consider setting it to Vabs.  And watering regularly.  :-)
    Regularly watering a valve regulated sealed battery might be a problem :smile:
    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