Sulfated beyond hope?

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  • pedro65pedro65 Registered Users Posts: 21
    Re: Sulfated beyond hope?

    The only thing that really runs when we are gone is the fridge. So most of the time, the system is using minimal electricity, probably less than 1kw/24 hours. I have the genset as backup if the batteries go below about 48v. That has been intermittent due to cold, and generator will blow a fuse occasionally. I have never been up there and seen the bank very low though.

    Panels are SW 175's 12 of them.

    I'll check out the inverter settings next visit. Everything was set by some of the folks that were helping me initially, and now I am not sure they are correct.
  • pedro65pedro65 Registered Users Posts: 21
    Re: Sulfated beyond hope?

    Sorry, getting a bit behind you on replies...

    Just to be clear, you think I should increase the standard absorb time....? I am sure it is set to 1 hour....Should the voltage be greater than 58 or so volts?

    thanks

    P
  • blackswan555blackswan555 Solar Expert Posts: 246 ✭✭
    Re: Sulfated beyond hope?

    Another thing to check while you are there, where is the BTS plugged in, the MX (charge controller) or the FX ? If MX , it will only work on MX, if FX it will work both FX & MX through hub,

    Have a good one
    Tim
  • blackswan555blackswan555 Solar Expert Posts: 246 ✭✭
    Re: Sulfated beyond hope?

    rolls say 57.6 – 58.8 - 60 min mean max v 2 hrs absorb, talking to a UK based rolls tech, he said, off grid absorb as long as you can, keep an eye on water, back voltage down a little if high, can cut your eq requirement right down, but if there is no one to check water, not a good option,
    I would go with mean ab voltage 58.8v (assuming you do have temp comp) 3 hr absorb,float 53.5v then plan a sunny day to do a full "by the book" eq (both charge sources to start) the info from the EQ should show any "bad " cells,

    Tim
  • VicVic Solar Expert Posts: 2,970 ✭✭✭✭
    Re: Sulfated beyond hope?

    Personally, YES, I think that you should increase your Asorb time. BUT, Asorb time and Voltage should really be determined by the ability of the system to MAINTAIN correct SGs -- ie fully charge the batteries during Asorb, and keep them charged during Float.

    If you discharge the batteries below 75% SOC, then I would increase the Asorb time. Perhaps try 1.5 hours, or more if fneeded. The 58 volt Asorb voltage is in the target range, but if you have too little Solar input at points in the winter, I'd increase Asorb voltage somewhat, as this can get more charge into the batteries during the time you have a charge source, especially true when running the generator. Asorb time and Voltage are critical to maintaining SGs. It will take some time, and monitoring SGs carefully to determine the ideal time and voltage for Asorb. It is possible to become obsessed in this process. Flooded batteries are forgiving, and Surrette is a good brand, so perfection is not required.

    Personally, it seems to me that the Asorb parameters need to be varied depending upon the depth of discharge, particularly the Asorb time, but am no expert in this.

    And if you could describe your system in a signature, you can get more accurate replies, and save a lot of typing on your part -- not being critical, but it will help. Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • Ralph DayRalph Day Solar Expert Posts: 887 ✭✭✭✭
    Re: Sulfated beyond hope?

    Being a ''finger on the pulse"kind of guy I like to vary those min mean max values as conditions permit/require. If the sg reading is 1.265 (had a streak of sunny weather...not now) I'll drop to the min numbers. After a gloomy streak, such as I'm especting this week the float and absorb will be the same max voltage until the sg comes back up. Really only works if you have your nose in the battery box daily, and aren't afraid to press the buttons on your charge controllers and inverters.

    Ralph
  • BB.BB. Super Moderators, Administrators Posts: 29,497 admin
    Re: Sulfated beyond hope?
    pedro65 wrote: »
    Unfortunately my physics is circa 1988 pre med classes, so I have been trying to bone up using a lot of the threads here.....I don't recall my inverter showing anywhere near 40 amps when the genset was charging....probably more along the lines of 15amps......is that the problem, not enough current?

    If the bank was "undercharged" why am I seeing a 51.9v or so in the afternoon after the sun is off the PV cells? Shouldn't the voltage drop precipitously once the charge current is gone if they are not fully charged? My charge controller was showing over 200 minutes of "float" time in the previous 5 days to my starting the EQ, I assumed that meant that the system was "full up"....

    Your bank should be around 5-13% rate of charge:
    • 700 AH * 0.05 = 35 Amps minimum sized charger
    • 700 AH * 0.13 = 91 Amps maximum sized charger
    The transition from Bulk to absorb probably occurs around 80-90% stage of charge--At that point, you will hit your absorb voltage (say ~58 volts) and hold it there for 1-6 hours... Probably in the winter with short days--6 hours is fine. In the summer and/or when you have very light loads, you could back it down to 2 hours or so...

    Then watch the electrolyte levels... You should be adding a bit of water every month... If you are adding near nothing--not enough charging/absorb time. If you are nearly exposing the plates in one month--then cut back on the absorb time/voltage some.

    After you have discharged the bank over night some (20% or so)--fire up the genset and see what the inverter/charger is outputting... How many amps, and how many volts (measure the voltage right at the inverter/charger terminals and at the battery bank--see how much voltage drop). Ideally, the charger should be outputting maximum current if the voltage is below your absorb set point. Once it is the absorb set point, the current will taper down a lot.

    If your battery bank is sulfated and has high resistance--this test is probably going to be difficult to do--your battery voltage will pop right up to the absorb voltage point.
    • 15 amps at 60 volts = 900 watts... That is a very light load for a 10 kW genset.
    • 35 amps * 60 volts = 2,100 watts into the battery
    • 2,100 * 1/0.80 charger efficiency = 2,625 watts from the generator
    • 91 amps * 60 volts * 1/0.80 = 6,825 watts from the generator
    What I am trying to get at here--You really want to be running your 10kW genset very near 50% (or heavier) of rated load for good fuel economy.

    The typical genset runs ~50% fuel flow at 50% rated load, and 50% fuel flow at 0% rated load... So, your optimum price point is a reasonably heavy load on your genset.

    So, I would suggest:
    • Check inverter/charger that it is capable of your desired current output (closer to 35-91 amps) programmed for correct amp output and the correct voltage set points.
    • Run the genset in the morning and just long enough to "bulk up" the battery bank to 80-90% state of charge--then let the solar panels take it the rest of the way (keep genset in fuel efficient zone). If you have optional loads (well pump to storage tank, washer/drier, vacuum cleaner, etc.)--run them at this time to get generator load to 50% (it is not going to cost you hardly any more fuel).
    • Depending on your fuel usage--it may be worthwhile to find a used 5-6kW genset (or even less, if your charger is 20 amps or so).
    • Also, if you have a small charger--it may be worth finding a larger charger to run in parallel with or instead of the inverter/charger (used forklift charger?).
    If you get a Battery Monitor and your bank heals itself (or you get a new one)... My suggested (spouse, kid, guest friendly) charging procedure:
    • If Battery Monitor reads 75% or less state of charge, shed loads and/or plan on running the genset next morning.
    • If Battery Monitor reads 50% or less state of charge, start genset right away.
    • Once genset is running--watch the charging current and battery state of charge... Once the charging current has been reduced (perhaps by 1/2 or so) and/or battery bank is over 80% state of charge--shut down genset.
    Anyway, from reading around here--that seems to be an pretty easy way to stay out of trouble.

    Note that Battery Meters are approximations... They typically reset to 100% when the bank is 100% charged (high voltage, low charging current). Double check once in a while with resting voltage and/or specific gravity readings.

    Watch charging currents (panels and generator is working OK) and discharging currents (especially at night and/or when there should should be light loads--see if something is on that should not be).

    -Bill

    PS: Above posted updated with correct numbers based on 700 AH battery bank instead of the 350 AH I used mistakenly...:blush:
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Solar Expert Posts: 4,994 ✭✭✭✭
    Re: Sulfated beyond hope?

    "Photowhit....that was the voltage with the inverter circuit breaker thrown and all loads off the bank...."

    "If the bank was "undercharged" why am I seeing a 51.9v or so in the afternoon after the sun is off the PV cells?"

    The reason I gave you several scenarios based on time, with different results, is that a battery is a chemical reaction, in which time is an important element. So is the sun and it's going to explode or collapse, knowing it won't happen any time soon is important.

    I don't think you read the part about reading voltage value at rest, after the battery has had no load or charging for 3-6 hours.

    NAWS has a great FAQ section on batteries Here;

    http://www.windsun.com/Batteries/Battery_FAQ.htm

    A great place to learn!

    It states "To properly check the voltages, the battery should sit at rest for a few hours,..."

    Many suggest at least 3 hours.

    I find many people new to solar to be alarmed and discouraged that they can't just know what the capacity they have in their batteries, I personally describe it as a feeling and discourage the use of meters as they are only as good as the numbers plugged into them, creating more alarm bells as they haven't been zeroed out or adjusted for aging batteries.

    That said watch your system (over time) and you'll likely get a good feeling of what is happening. It does sound like your SG is low and likely an equalizing, will raise it.

    Rolls are great batteres and it appears they have a vigilant owner, always a good thing!
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • blackswan555blackswan555 Solar Expert Posts: 246 ✭✭
    Re: Sulfated beyond hope?

    BB, I believe the OP`s bank is 700 ah @ 48v ? 8 bats x 6v x 2 strings ?
    The battery bank is 16 S-460 Surrettes

    Have a good one
    Tim

    Pedro, please fill your profile in, It saves having to troll through posts looking for info.
  • BB.BB. Super Moderators, Administrators Posts: 29,497 admin
    Re: Sulfated beyond hope?

    Tim/BlackSwan555,

    You are correct... He has 700 AH of battery bank.

    I have updated my previous post and will go to bed now.

    -Bill "irrational numbers R I" B. :blush:
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jeffkrusejeffkruse Solar Expert Posts: 205 ✭✭✭
    Re: Sulfated beyond hope?

    I have my absorb time set to max. I also raised my voltage to 60V.

    I used the "default" settings for my first set of batteries. After several months my SG was to low. It was maddening to see the charger in float mode but the SG on the batteries low.

    It took a very long EQ to correct the problem.

    Now with my absorb time at max and the voltage raised a bit my SG is ok.
  • pedro65pedro65 Registered Users Posts: 21
    Re: Sulfated beyond hope?

    Thanks again all.....Going to make the changes my next trip up.

    I thought I had filled in my profile?
  • BB.BB. Super Moderators, Administrators Posts: 29,497 admin
    Re: Sulfated beyond hope?

    Fill in your signature and the next time you post (or edit your last post), click on the "show your signature" box in the "additional options" section just below your Post Edit area/Submit Reply buttons... Then all of the rest of your posts will have your system setup.

    I will edit your "signature" and your last post to show your signature.

    -Bill

    PS: By the way, I made a mistake and you have a 700 AH battery bank... You have to 8 battery strings (each 8x 6volt batteries = 48 volts; the two strings are connected in parallel for 2x 350 AH = 700 AH; for your total of 15 S-460 batteries--each rated at 350 AH and 6 volts).

    PPS: I am only a moderator here--I cannot update your "Interests" section in your profile.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SchmidtSchmidt Registered Users Posts: 12
    Re: Sulfated beyond hope?

    pedro65,

    Check your PM.

    Caleb Schmidt
  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: Sulfated beyond hope?

    Looks like new batteries may be in order. Make sure the voltages on the charge controler are set correctly. My MX60 & FX80 defaults were too low acording to the Trojan website. http://www.trojanbattery.com/BatteryMaintenance/Charging.aspx
  • VicVic Solar Expert Posts: 2,970 ✭✭✭✭
    Re: Sulfated beyond hope?

    Hi Pedro,

    Thanks for filling out your signature profile (and Bill for turning it on). This helps. However, could you detail your 'Outback' equipment. This additional info willl help.. Often, we guess incorrectly about the hardware in the system.
    Good Luck with the batteries. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • bluetickbluetick Registered Users Posts: 19
    Re: Sulfated beyond hope?

    I've been reading this forum for a bit. I found this information from the book "Automotive Storage Battery It's Care and Repair" published in 1922 by O.A. Witte.

    The sulphate thus forms a high resistance coating which hinders the passage of charging current through the battery and causes heating on charge. It is for this reason that sulphated plates should be charged at a low rate. The chemical actions which are necessary to change the sulphate to active material can take place but very slowly, and thus only a small current can be absorbed. Forcing a large current through a sulphated battery causes heating since the sulphate does not form uniformly throughout the plate, and the parts which are the least sulphated will carry the charging current, causing them to become heated. The heating damages the plates and separators, and causes buckling.
  • BB.BB. Super Moderators, Administrators Posts: 29,497 admin
    Re: Sulfated beyond hope?

    Bluetick,

    That sounds reasonable--Rolls/Surrette recommends a maximum of 5% current during equalization to try and reverse sulfate hardening/crystallization. Of course--when equalizing, most of the energy is going into turning water into hydrogen and oxygen. No reason to pump high current into a fully charged battery just to electrolyze water.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • pedro65pedro65 Registered Users Posts: 21
    Re: Sulfated beyond hope?

    An Update:

    The battery bank is working much better after weeks of bright sunshine and cool days and resetting to high voltage and maximum absorb times. I have performed a couple of corrective EQs, and though they didn't seem to raise the SG right away, my test cell is now reading at about 1.250. This is pretty good, considering that I was unable to get it above 1.23 for quite a while. Unfortunately I am only at the house a couple of days, so am unable to recheck each day.

    A couple of related questions:
    If you top off a cell, it seems to me that is going to lower the SG, and that the SG will rise as the total volume of electrolyte (H2O) is depleted leaving more dissolved solute. Am I getting falsely high SG because the electrolyte is evaporating?

    How do you control the current flow from the CC during EQ? Even though my battery bank was nominally full, if I set a 62V EQ, it seems as if the amps would be elevated, preventing the CC from reaching the voltage. If I dropped the requested voltage to 61V, the amperage decreased and the voltage was met. Is the amperage strictly a function of the battery bank SOC and PV input or am I missing something?

    Finally, how does the CC interact with the inverter? If I run the genset while EQ with the PV, how do those two systems interact?
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