XW6048 equalize duration

Brent
Brent Solar Expert Posts: 64 ✭✭✭✭
I did an equalize for the first time on a three month old system. 6500 watt PV with two XW6048's and an 850 AH battery system. The equalize worked fine but lasted for only 1 hour and 15 minutes. Is this duration fixed or variable?

Thanks,

Brent

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,422 admin
    Re: XW6048 equalize duration

    I am not sure if the timer is programmable, but you should check the specific gravity every 30 to 60 minutes and stop the equalization once the s.g. stops rising.

    Hours of equalization is hard on a battery bank and should only be performed when needed and only long enough for all cells to be fully charged.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Brent
    Brent Solar Expert Posts: 64 ✭✭✭✭
    Re: XW6048 equalize duration

    Thanks for the reply. Is it even necessary to equalize if the SG is showing full charge? Even after several months?

    Brent
  • BB.
    BB. Super Moderators, Administrators Posts: 33,422 admin
    Re: XW6048 equalize duration

    Roughly, for a flooded cell battery, you should equalize when there is a 0.030 or greater difference between the high and low cells. (Trojan battery manufacturer).

    Equalization is very hard on a battery and should only be done if needed.

    After you have "fully charged" bank, write down the cell readings so you can track over time.

    Equalization can cause plates to shed material and electrolysis drives oxygen into the positive plate grid support, causing corrosion (swelling of positive plates, pushing up the positive terminals and swelling the case).

    How much current do you push into the battery bank when charging.

    Too high or too low of charging current can cause problems too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    Re: XW6048 equalize duration

    I personally would not equalize longer then an hour. It is hard on batteries.

    Looking through the op manual it looks like there is only voltage setting and enable/disable of user control on equaliztion. I could not even find where it said it lasted one hour other then example display screen showing time remaining.

    A lot depends on what level you set absorb voltage with regard to need for equalization.
  • Brent
    Brent Solar Expert Posts: 64 ✭✭✭✭
    Re: XW6048 equalize duration

    Thanks all for the input.

    For reference I have 16 - 6 volt at 415 AH deep discharge batteries wired in series/parallel to produce 48 V nom. at about 830 AH. The batteries are also wired in a cross link configuration. We live on-grid in the country and the power frequently goes off for several hours during the winter so the batteries really don't get a allot of discharging during the year.

    The XW6048 is programmed to the battery manufacturers charging specs of:
    Bulk: 57VDC
    Abs: 59VDC
    Float: 52.8 VDC @ 25C
    EQ: 64VDC

    The inverter charger is disabled and the batteries rely on the charge controllers to provide the bulk/abs charge each morning which usually takes about half an hour then the system goes into sell when the chargers switch to float.

    When I did the equalize the voltage ramped up to about 62 volts and the current was held at a constant 12.5 amps into the battery bank as indicated on the Bogart battery monitor.

    Brent
  • BB.
    BB. Super Moderators, Administrators Posts: 33,422 admin
    Re: XW6048 equalize duration

    That sounds a bit light on the equalization current--but if you batteries sit at float most of the time--you probably are not going to get a lot of current into them.

    Another question, what is the Sell Voltage set to?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Brent
    Brent Solar Expert Posts: 64 ✭✭✭✭
    Re: XW6048 equalize duration

    Bill,

    I have the sell voltage set to 64 volts. I updated the chargers to the latest firmware which has the "smart charger" feature and allows this setting rather than setting it near the float voltage. Works fine.

    Brent
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    Re: XW6048 equalize duration
    Brent wrote: »
    Bill,

    I have the sell voltage set to 64 volts. I updated the chargers to the latest firmware which has the "smart charger" feature and allows this setting rather than setting it near the float voltage. Works fine.

    Brent

    So you are never selling since your battery never reaches 64v.

    It is set way too high. Sell should be slightly below float level voltage.

    Do you also have an XW charge controller with Xanbus connection between inverter and charge controller?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,422 admin
    Re: XW6048 equalize duration

    Should be closer to 54 volts for sell voltage...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    Re: XW6048 equalize duration

    What would make sense for an XW inverter with Xanbus connected XW charge controller is software that ignores battery sell voltage setting.

    When charge controller wakes up in morning it allows battery charging through absorb period THEN, if sell is enabled, sells at a rate to bring battery back down to, and maintain, float voltage setting. Float level is effectively sell level setting.

    I would call this a 'smart sell' SW upgrade.

    It still needs to have sell voltage setting for non-Xantrex charge controllers.

    Maybe this is what you are referring to in the 'smart charger' firmware upgrade.
  • Brent
    Brent Solar Expert Posts: 64 ✭✭✭✭
    Re: XW6048 equalize duration

    I am not the expert on the "smart charge" feature in the latest charge controller upgrade but as it was explained to my by a Xantrex Tech the new firmware for the charger allows the sell function to start after the chargers complete the absorption cycle from PV power and does not rely on setting the inverter "sell" voltage.

    I was told to set the sell voltage on the inverter to above 60 volts to "get it out of the way" so the chargers can control the sell function. Mine is set up that way and sells just fine.

    Brent
  • BB.
    BB. Super Moderators, Administrators Posts: 33,422 admin
    Re: XW6048 equalize duration

    Interesting--What voltage does your system "sell" at?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Brent
    Brent Solar Expert Posts: 64 ✭✭✭✭
    Re: XW6048 equalize duration

    Bill,

    The inverters sell at the charger float voltage setting, about 52.8V, in my
    case, depending on the battery temp. After the chargers complete the absorption cycle in the morning the inverters will go into the sell mode. This is with the inverter sell voltage set anywhere above 60V.

    If your charge controller has ver 5.x firmware [included in units sold after Feb 2010] you might give it a try. Works great and you don't have to fiddle with the inverter sell voltage settings.

    For some reason this feature is not in the instruction manual or otherwise published as far as I can tell. I only found out because the tech at Xantrex mentioned it when I updated to the latest charge controller firmware ver.

    Brent
  • BB.
    BB. Super Moderators, Administrators Posts: 33,422 admin
    Re: XW6048 equalize duration

    Sounds perfect... I have pure grid tie--but it will be of great interest to others here.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,722 ✭✭✭✭✭✭
    Re: XW6048 equalize duration

    In the custom battery menu you can set the voltage that "the battery manufacturer reccomends". Keep in mind that if you skip the maintenance in this regard, your battery can be permenantly damaged. Preventative EQ's are generally done every 90 days on the Surrettes after a full charge.

    As for EQ with the xwcc it has always worked since day one and is in the xwcc manual. Am I missing something here?
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail [email protected]

  • Brent
    Brent Solar Expert Posts: 64 ✭✭✭✭
    Re: XW6048 equalize duration

    Thanks for the replys.

    I have read that batteries that are discharged allot should be equalized on a regular basis. I do mine every three months regardless. What I am wondering, is it still necessary to equalize batteries that show a full charge specific gravity and are held at float all the time and infrequently discharged?

    I also read that batteries kept at full charge [above 80%] will not sulfate.

    Just trying to improve my understanding here.

    Thanks,

    Brent
  • BB.
    BB. Super Moderators, Administrators Posts: 33,422 admin
    Re: XW6048 equalize duration

    In general, you are correct...

    The specifics of battery chemistry are a whole bunch of trade-offs to optimize battery life (too high of float voltage, gassing corrosion, too low of voltage sulfates, etc.).

    Low charging current, efficient charging and long battery life... Too low of charging current, no mixing allowing stratification of electrolyte--bottom of cell "overcharged", top of cell undercharged, etc.

    Read the comments of the people here who live off grid (Dave Sparks and others) who have their own systems (and, many times, like Dave Sparks, have years of business experience supporting off-grid clients) on how to take care of the battery bank.

    Me I am on grid--So I am not the best to give detailed advice. Generally, I try to stay with the general theme of good battery practices so nobody "toasts" their banks in short order.

    Here is a post where I tried to put much of good practices into one post:
    BB. wrote: »
    No, do not equalize unless the cells s.g. is miss-matched or one or more cells are low s.g. while the rest are high.

    Equalizing once every one-two months as a starting point should be OK.

    Remember, equalization is pretty hard on a battery bank and really should only be performed when conditions warrant.

    Here is a thread on Specific Gravity versus voltage. And, the voltage difference of 0.2 volts between cells is probably way to high... That is probably almost the difference between a "full" and a "dead" cell's voltages.

    Form the above link, the formula for specific gravity to voltage is:

    • Specific gravity = single-cell open-circuit voltage - 0.845
    • (example: 2.13v – 0.845 = 1.285)
    • Or:
    • Single-cell open circuit voltage = specific gravity + 0.845
    If we use the Trojan value of SG 0.030 difference in Specific Gravity between cells as a point at which to equalize--that would be 0.030 volts between cells.

    From Trojan's battery manual (PDF):
    Equalizing (flooded/wet batteries ONLY) 3.4.2.

    Equalizing is an overcharge performed on flooded/wet batteries after they have been fully charged. Trojan recommends equalizing only when batteries have low specific gravity, below 1.250 or wide ranging specific gravity, 0.030, after fully charging a battery. Gel or AGM batteries should never be equalized.
    • Confirm that the batteries are flooded/wet
    • Check electrolyte level to make sure plates are covered with water before charging
    • Check that all vent caps are secured properly on the battery before charging
    • Set charger to equalizing mode
    • The batteries will gas (bubble) during the equalization process
    • Measure the specific gravity every hour. Discontinue the equalization charge when the gravity no longer rises
    WARNING: Do not equalize gel or AGM batteries
    I like Dave Sparks' post:
    I learned this strategy from Dave Surrette (Rolls) in the late 70's. Pretty much the bible on how I design my systems for off-grid.

    Assume that the system will never reach more than a 90% state of charge.
    Try not to go below 50% SOC, ever! Complete absorption over 90% of the year

    Use the energy stored from 70% to 90% SOC for your daily cycles.
    Save the energy from 50% SOC to 70% SOC for aging to get long battery life.

    I know Surettes has changed their recommendations over the years but I also know they are in the business of selling batteries! If you do the above you will get 10 to 15 years on their batteries with decent maintenance.

    The OP is making it complicated by mixing battery types and not really stating a lot of information that would allow decent specific advice.

    Oh yea, I am really happy that Surrette and Trojan are making L16's with 1000 AH capacities @20HR. Been bugging them for many moons to do batteries less than 125LB's!

    And, my two cents... If your batteries are using a bit of distilled water per month--you are probably OK. If you are using none, or a lot per month--then you are probably under or over charging.
    • Undercharging and operating for long periods (below ~75%) is damaging to lead acid batteries.
    • Overcharging is less damaging to flooded cell batteries (at the cost of distilled water and wasted energy).
    • Overcharging sealed batteries (AGM, Gel, VRLA, etc.) can be fatal to those types (venting electrolyte).

    -Bill

    PS: Add the standard Battery FAQ's for completeness:

    Deep Cycle Battery FAQ
    www.batteryfaq.org
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    Re: XW6048 equalize duration

    There are two opposing curves associated with float voltage for positive plate and negative plate.

    The float point is in the compromise 'well' of the two curves. This point changes with temperature of battery.

    Negative plates like higher float voltage to keep them from sulfating.
    Positive plates like lower float voltage to keep them from corroding and excessive lead oxide build up.