Batteries bulging, What's up?

bc buck
bc buck Registered Users Posts: 59 ✭✭
in General Solar Power Topics #1
While doing maintenance I noticed positive terminal side of all 4 of my wet 6 volt cart batteries slightly bulged. They where put on line January 2017 and not abused. Only get about 50 50% discharges a year. Did get down to -15f once this winter but should have been fully charged. Also batteries seem to still hold close to new on the AH.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,626 admin
    #2
    As I understand, positive post "extrusion" is typically the result of positive grid corrosion typically caused by "over charging / over equalization". When you charge a battery at 100% state of charge, the energy is turned into H2 and O2 gasses. The good thing is this mixes up the electrolyte and reduced stratification issues (low density at the top of the cell and high density electrolyte at the bottom). The bad thing is that the O2 forms at the positive plate and causes grid (and probably lead) oxidation--causing the plates to "grow" and put the positive post up and bulge the sides of the case.

    This can apply to the standard Lead Acid batteries out there (flooded cell, AGM, GEL)--As I understand.

    Getting ~4 years out of "golf cart" batteries is doing OK (3-5 years?). You can check the charging voltage and absorb time. Possibly reduce the amount of "gassing" on your bank.

    -Bill "not a battery engineer" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • jtdiesel65
    jtdiesel65 Solar Expert Posts: 242 ✭✭✭
    #3
    From what I read, positive plate growth is normal. It's an aging process that can be sped up.  My forklift battery lasted 9-10 yrs, but plate growth was obvious toward the end. I wouldn't worry about "slightly" bulged, but it's possible that the cases could crack if it gets worse. I know the cases on my cells were strained to the max at the end.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,626 admin
    edited August 2021 #4
    JT is correct... I did not do a good job of stating in my post, positive plate growth is part of the normal aging process--It cannot be stopped cold.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • bc buck
    bc buck Registered Users Posts: 59 ✭✭
    #5
    BB. said:
    As I understand, positive post "extrusion" is typically the result of positive grid corrosion typically caused by "over charging / over equalization". When you charge a battery at 100% state of charge, the energy is turned into H2 and O2 gasses. The good thing is this mixes up the electrolyte and reduced stratification issues (low density at the top of the cell and high density electrolyte at the bottom). The bad thing is that the O2 forms at the positive plate and causes grid (and probably lead) oxidation--causing the plates to "grow" and put the positive post up and bulge the sides of the case.

    This can apply to the standard Lead Acid batteries out there (flooded cell, AGM, GEL)--As I understand.

    Getting ~4 years out of "golf cart" batteries is doing OK (3-5 years?). You can check the charging voltage and absorb time. Possibly reduce the amount of "gassing" on your bank.

    -Bill "not a battery engineer" B.
    Im using a Morningstar prostar mppt and dropped to lower of the two options for wet cells. Absorp 14.6, float 13.5 and been running auto once every 28 days equalize. Thinking of going to manual equalize and running it every 60 days because I need to add 1/2" water to each sell about every 45 days.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,907 ✭✭✭✭✭✭
    #6
    The problem that is often the cause, is you really are not doing an equalize like you think you are. Non networked power systems do not give a graphical display. You need to see, or know that you really did an EQ. This is often the problem in small systems. Loads or clouds are stopping you from staying at the set point!  Batteries are expendables offgrid, you do have to replace them! Below is what not to do!


     
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • bc buck
    bc buck Registered Users Posts: 59 ✭✭
    edited June 2021 #7
    Dave Angelini said:
     This is often the problem in small systems. Loads or clouds are stopping you from staying at the set point!  Batteries are expendables offgrid, you do have to replace them! Below is what not to do!
    This is why I have always used cheap wet cell banks. First couple sets of batteries I toasted in a year or two. Did some research using this forum and have been pretty happy with my current setup. Would like to try next set of batteries using something that does not need the maintenance or give off gassing. The thought of destroying expensive batteries scares me to death.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,907 ✭✭✭✭✭✭
    #8
    Being electrocuted could be scary.  As long as you are safe, informed, and read the manuals, none of this should be scary.
    Setting off across the Pacific ocean on a Kayak is scary  ;)
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • boB
    boB Solar Expert Posts: 1,032 ✭✭✭✭
    #9

    I usually see this happen with AGMs or gel batteries but any one of them can bulge.  They plump when you cook 'em !

    I also found that in my case, the batteries become "unbalanced"...  That is, one battery will become charged more or less than others in the string of batteries.   The voltage on one battery will be higher than the others and will become hotter.

    If you have a thermal imager camera or just a good thermometer, you can see if one battery is hotter than the others while charging and/or inverting. You can also just measure the terminal voltages of the individual batteries (not the cells but the whole battery) and usually the one that is going to bulge will be different than the others in the series.

    Of course, one of the batteries or its cells could be damaged or out of electrolyte.

    My 2 cents worth.


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  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,174 ✭✭✭✭
    #10
    I have seen many, many batteries bulging due to chronic undercharging and the resulting extreme sulphation.

    Marc
    I always have more questions than answers. That's the nature of life.
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  • jtdiesel65
    jtdiesel65 Solar Expert Posts: 242 ✭✭✭
    #11
    Marc Kurth said:
    I have seen many, many batteries bulging due to chronic undercharging and the resulting extreme sulphation.

    Marc
    That sounds like typical life of a solar charged battery. 

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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,907 ✭✭✭✭✭✭
    #12
    Certainly seems like many of the LA batteries on this forum. There are also people who do it right!  Some replace solar charged batteries at 15 years, just because they do not want a winter failure. The other way is just having a 2nd bank. This is where LFP can shine as it can just sit until needed.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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