How do SGs change as batteries age?

WaterWheelWaterWheel Registered Users Posts: 242 ✭✭✭
My LA batteries are 14 months old now, carefully watered, EQ every 4-6 weeks and generally the cells are fairly close in SG after an EQ.     After the first 2 months (broken in)  the batteries averaged 1.277 SG.     A year later the average SG after an EQ and 3 hr rest is now 1.268.      I guess I could EQ the hell out of them but judging from SG readings during an EQ I don't think they would come up much more if I cooked them.

Is this normal for batteries as they age?      As determined by SG reading I generally cycle between 93% SOC and 75% SOC daily, rarely getting below 65% SOC.

Conext XW6848 with PDP, SCP, 80/600 controller, and conext battery monitor

18 SW280 panels on Schletter ground mount

48v 790 amp/hr Crown battery bank

Comments

  • PhotowhitPhotowhit Solar Expert Posts: 4,280 ✭✭✭✭
    edited December 2016 #2
    Are you compensating for temperature? Even after 3 hours the battery might still be warm. particularly a large mass like a forklift battery. Might be part of the problem.

    Chart here;
    http://support.rollsbattery.com/support/solutions/articles/208145-specific-gravity-temperature-correction-factors
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • mike95490mike95490 Solar Expert Posts: 7,307 ✭✭✭✭
    The longer batteries sit less than 95% charged, the sulfur is starting to lock onto the plates.  ReCharging forces it back into the solution and the SG goes up.   Over time, a little bit more sulfur gets stuck on the plates, and becomes harder and harder to dissolve, and your SG slowly starts going down, Eventually so much sulfur gets trapped in the plates, the battery looses all usable capacity.
    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 ,

  • WaterWheelWaterWheel Registered Users Posts: 242 ✭✭✭
    edited December 2016 #4
    I use a hydrovolt SG meter so yes, measurements are temperature compensated.       

    A very knowledgeable member on this site (I think it was Bill or Vic ) put forward a strong argument that attempting to charge much over 90% SOC daily  (excess water usage and heat)  may not be the best thing.     That combined with a call I made to the Crown battery manufacturer tech who wanted me to get above 1.265 at least several times a week has me currently allowing the batteries getting charged to about 1.265% SOC most days.

    So I guess the question is as a battery ages is it normal to see capacity to drop about 4-5% a year?

    Conext XW6848 with PDP, SCP, 80/600 controller, and conext battery monitor

    18 SW280 panels on Schletter ground mount

    48v 790 amp/hr Crown battery bank

  • PhotowhitPhotowhit Solar Expert Posts: 4,280 ✭✭✭✭
    edited December 2016 #5
    No not usually, I wonder now if you were sure the batteries were fully charged before you equalized?

    I have a 5 yr old forklift battery of a lesser grade (GB) and 11 cells are fine in the 270-285 range when fully charged. I have one bad cell, that I think was poisoned. I've extended the absorb time to 3hrs now and the cell is maintaining a higher SG when the charger shuts down @ 1.255 I hope the next chance I get to equalize and monitor, will bring it up the little extra. I suspect it has lost a good bit of capacity even if brought back into line.

    The equalizing cycle on a charge controller or a charger is just that, and good for a Maintenance equalizing when batteries are in good shape, it will help mix the electrolyte and do allow for some correction. Corrective equalizing will help remove sulfates that have hardened on the cell and either put them back into solution (ideal) or have them fall off and drop to the bottom of the cell(not so great). I would continue to equalize and see if your cells don't come up more. Corrective equalizing is done on a fully charged battery and SG is checked and recorded hourly. When no cell improves after 2 hours you are likely at the best recovery you can expect.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • WaterWheelWaterWheel Registered Users Posts: 242 ✭✭✭
    I shoot for about a 10 amp cutoff for absorb on the 790 amp/hr battery bank but that was only giving me about a 1.260 SG after 4 hrs.     Manufactures spec for absorb is 58.1v.     After talking to crown tech support last summer about low SGs after 4 1/2 hr absorb cycles  they suggested that I bump it up to 58.5v absorb but they warned me to keep an eye on things so that I didn't overcharge.       They wanted to see at least a 1.265 SG at the end of absorb but really didn't like me going above 58.1v for the absorb voltage.       It helped a little although I still had to keep it into absorb until about a 9 amp current at the end of absorb in order to get to 1.265 SG.       Even after equalizing I was noticing SGs were very slowly dropping ofer the months after equalizing so...

    A few days ago I gave it 8 hrs of absorb over 2 days (batteries rested between absorb cycles, no load) at 59.1v.     The bank was drawing 7.5 amps at the end.        I then EQd for 4 hours  at factory specified 61.9v but saw little change in SGs after the first 2 hrs.     Four hour rest before testing.        Average SG is now 1.271 so better but...   I think that's the limit.

    What am I doing wrong?        I'm beginning to suspect that Crown has too low of an absorb voltage published and by following it for the first 10 months I had the batteries I may have damaged them by following their charging specifications.

    After doing a bit of research for other battery manufacturers with L-16 batteries
    Trojan says absorb at 59.2v
    Rolls shows 60.0v absorb
    Crown Deep Cycle wants 59.5v absorb
    My Crown 6CRP525 paperwork wants 58.1v absorb.      Crown tech support on the phone was weary of going up to a 58.5v absorb.

    Conext XW6848 with PDP, SCP, 80/600 controller, and conext battery monitor

    18 SW280 panels on Schletter ground mount

    48v 790 amp/hr Crown battery bank

  • westbranchwestbranch Solar Expert Posts: 4,873 ✭✭✭✭
    Did you verify that that was the Voltage at the battery and not just the charger setting?  A loose/warm/hot connection?
    Try a longer absorb at 58.3V, for 16 hrs???  just trying to brain storm...
    hth
     
    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, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • WaterWheelWaterWheel Registered Users Posts: 242 ✭✭✭
    Yes,     With 2 different multi-meters and the Conext battery monitor.    All 3 matched.       I've also verified the charging amperage with a clamp meter.

    Conext XW6848 with PDP, SCP, 80/600 controller, and conext battery monitor

    18 SW280 panels on Schletter ground mount

    48v 790 amp/hr Crown battery bank

  • westbranchwestbranch Solar Expert Posts: 4,873 ✭✭✭✭
    I guess lengthening the Absorb time is next....  I really noticed the difference when I shortened the Absorb time this summer, early AM voltages were up to 2/10 ths lower with just the Fridge and Net (modem&router) on overnight so I moved it back up... guess I hit the sweet spot by accident, now I just drop the Abs Voltage in summer when I get tons of input... so don't get an over Abs event... which I got daily...
     
    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, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • WaterWheelWaterWheel Registered Users Posts: 242 ✭✭✭
    edited December 2016 #10
    But with the ending absorb rate being about 1% of battery capacity while charging at a higher voltage the factory lists I would assume the SGs would be over 1.268 (95% SOC) instead of the 1.258 - 1.260 I'm currently seeing.

    When the batteries were only 6 months old and I could get the SG up to 1.277 I didn't worry about it but now I can't get them all the way up.

    Conext XW6848 with PDP, SCP, 80/600 controller, and conext battery monitor

    18 SW280 panels on Schletter ground mount

    48v 790 amp/hr Crown battery bank

  • Dave AngeliniDave Angelini Solar Expert Posts: 3,329 ✭✭✭✭
    Around 2 weeks to the solstice on my calender? Just a guess but it sounds like you are overthinking this :)
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail offgridsolar@sti.net

  • westbranchwestbranch Solar Expert Posts: 4,873 ✭✭✭✭
    edited December 2016 #12

    In post #8 you EQ'ed.  did you get a lot of mixing (bubbling)? How hot did the battery get?
    Have you tried an EQ daily for 2 or 3 times?

    with the ending absorb rate being about 1% of battery capacity

    that being the case I think you will have to do A,B & C as a set

     A) go closer to or equal  to near zero %  (EA 4 amps?) ie, stay in Absorb daily over the winter

     B ) start at the recommended Absorb voltage [ and increase in increments of .2V if you are not happy (after the first  week or so) ]

     C) do an EQ with the gen every 2 to 3 days, or daily, to see if you can maintain or gain on the SG readings.

    All this is a process of discovery.  "The truth is out there..... somewhere'' Fox Mulder

    hth




     
    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, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • WaterWheelWaterWheel Registered Users Posts: 242 ✭✭✭
    edited December 2016 #13
    Around 2 weeks to the solstice on my calender? Just a guess but it sounds like you are overthinking this :)

    I suspect you may be correct.  

    Last night we went out for 7 hrs so I used the mini split to heat the house with outside temperatures dropping below 30 while we were gone.        It really dropped the batteries to the point to where I didn't enter absorb until 1pm today.      Still,    I'm very impressed with the mini-split.     Thanks for your earlier posts about mini splits.       Mine is primarily for cooling but is sure is nice for occasional heating.

    Conext XW6848 with PDP, SCP, 80/600 controller, and conext battery monitor

    18 SW280 panels on Schletter ground mount

    48v 790 amp/hr Crown battery bank

  • WaterWheelWaterWheel Registered Users Posts: 242 ✭✭✭

    In post #8 you EQ'ed.  did you get a lot of mixing (bubbling)? How hot did the battery get?
    Have you tried an EQ daily for 2 or 3 times?

    with the ending absorb rate being about 1% of battery capacity

    that being the case I think you will have to do A,B & C as a set

     A) go closer to or equal  to near zero %  (EA 4 amps?) ie, stay in Absorb daily over the winter

     B ) start at the recommended Absorb voltage [ and increase in increments of .2V if you are not happy (after the first  week or so) ]

     C) do an EQ with the gen every 2 to 3 days, or daily, to see if you can maintain or gain on the SG readings.

    All this is a process of discovery.  "The truth is out there..... somewhere'' Fox Mulder

    hth





    A fair amount of bubbling while equalizing, The batteries went up from 58 degrees to 75 degrees during that long multiple absorb and EQ session.

    In the past I've considered equalizing every few days but figure I would probably do more damage than good in the long run.

    Thanks for helping with this.

    Conext XW6848 with PDP, SCP, 80/600 controller, and conext battery monitor

    18 SW280 panels on Schletter ground mount

    48v 790 amp/hr Crown battery bank

  • mcgivormcgivor Registered Users Posts: 1,304 ✭✭✭✭
    Somewhere I read that if the SG is low, a corrective equalization should be performed and this process can take upwards of 15 hours, with close monitoring temperature  and SG. The author stated that the battery should not be cycled, hense no loads during or in between sessions  as the prosess can take several  days. The temperatures  stated were in degrees celsius, and it was noted that above 45 deg.C to terminate if temperatures are rising. 70 deg F is an ideal starting point temperature, additionally it was stated that  if the SG was not increasing after one hour of the maximum SG  reading, there was no point in continuing the process.
    What I've read, take it for what it is worth.
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • Dave AngeliniDave Angelini Solar Expert Posts: 3,329 ✭✭✭✭
    Around 2 weeks to the solstice on my calender? Just a guess but it sounds like you are overthinking this :)

    I suspect you may be correct.  

    Last night we went out for 7 hrs so I used the mini split to heat the house with outside temperatures dropping below 30 while we were gone.        It really dropped the batteries to the point to where I didn't enter absorb until 1pm today.      Still,    I'm very impressed with the mini-split.     Thanks for your earlier posts about mini splits.       Mine is primarily for cooling but is sure is nice for occasional heating.
    You are welcome! The mini-splits are amazing to me still after 10 years. They save so much firewood and some are now at close to 5 times as efficient heating as resistance heating. Have a solstice back there!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail offgridsolar@sti.net

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