found some gel cells for sale, your advice please

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ozarkgem
ozarkgem Registered Users Posts: 21 ✭
in Off Grid Solar & Battery Systems #1
I have found some 1 yr old 12v 75 amp hr gel cells for sale locally. They have never been installed. 13 batteries for 650.00. I was going to get the
forklift battery but now reconsidering. Do gel's have to be equilized? Is setting for a yr going to hurt them? I will have 3000 watts of panels. Will
get the Midnite charge controller for them. So what do you all think? One more thing, what is the life of the gel cells?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #2
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    Re: found some gel cells for sale, your advice please

    One year of not charging.... May have been killed with sulfation.

    Gel batteries typically require low charging current... May not be a good match for solar charging.


    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
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    Re: found some gel cells for sale, your advice please

    Do not waste your money.
    First of all, gel batteries are not suitable for solar applications. They do not like high Voltage or current. If you were to equalize them, they would fry instantly. In other words they have no tolerance for "mistakes". Nor do they have good performance in terms of delivering power.
    Second, a bunch of 75 Amp hour batteries is a pain to put together. Getting fewer batteries of larger capacity to meet your needs will make you happier.
    Third, used batteries in general are worth scrap metal price. Sometimes less. No matter what the seller says, there is no practical way to check them out and see if they're any good. Even batteries that have not been used go bad just from sitting around.

    Again, do not waste your money.
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  • ozarkgem
    ozarkgem Registered Users Posts: 21 ✭
    #4
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    Re: found some gel cells for sale, your advice please

    good enough. back to the forklift battery. thank you very much
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #5
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    Re: found some gel cells for sale, your advice please

    Hi Ozark,

    Did you ever figure out the PM?

    I was asking for info on the battery guy, only if he has more or does this sort of thing for a living, and passing along some info about a cheap E-panel for your magnum inverter...

    I'll resend if you need me to...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • SandyP
    SandyP Solar Expert Posts: 65 ✭✭
    #6
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    Re: found some gel cells for sale, your advice please
    ozarkgem wrote: »
    I have found some 1 yr old 12v 75 amp hr gel cells for sale locally. They have never been installed. 13 batteries for 650.00. I was going to get the
    forklift battery but now reconsidering. Do gel's have to be equilized? Is setting for a yr going to hurt them? I will have 3000 watts of panels. Will
    get the Midnite charge controller for them. So what do you all think? One more thing, what is the life of the gel cells?

    Hi,
    As per my signature I do have some GELs and they can be equalised. I also understood that their self discharge rate is lower than FLA batteries however it depends on temperature etc. This from Exide :
    3.3 Storage Time
    The maximum storage time at <= 20° C is
    24 months for standard Gel-batteries (fig. 1) and
    17 months for Gel-solar batteries (fig. 2).
    The shorter storage time of solar-batteries is due to a small amount of
    phosphoric acid added to the electrolyte. Phosphoric acid increases the
    number of cycles but increases the self-discharge rate slightly.
    Higher temperatures cause higher self-discharge and shorter storage time
    between recharging operations.
    Attachment not found.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #7
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    Re: found some gel cells for sale, your advice please

    Sandy,

    Most charts I have seen for "other" lead acid batteries (flooded cell/AGM/etc.) seem to show the "recharge" point for batteries in storage at ~75% state of charge. I have assumed batteries stored below those points would tend to sulfate at a much faster rate. Are GEL batteries less susceptible to sulfation?

    Also, what do you mean by equalization for GEL batteries. In general, the maximum rate of charge for I have seen for "typical" GEL batteries is around 5% or C/20 rate of charge.

    Higher charge rates would tend to form gas pockets in the GEL--which leads to unrecoverable loss of capacity/output current due to the bubbles in the GEL.

    While you could probably "equalize" a GEL battery--It would be similar to the recommendations that I have seen for AGM type batteries--Not an elevated voltage (~15-15.5 volts for a flooded cell battery), but just an extended absorb charging voltage (~14.2-14.4 volts) past the typical end point for Absorb phase charging.

    A major reason I would understand GEL are not great for "typical" off grid systems is the C/20 charge rate and the fact that most off grid users can use power anytime in a 24 hour period.

    If your maximum charging current is C/20 (5%), and you use power during the day, it is very "easy" to use much of the C/20 charging current to power loads during day (computer, pumping, washing clothes, TV, etc.) and get the rate of charge down to near zero (or less).

    If you have enough charging current to support a reasonably small load during the day (say C/20), then your total available charging current is C/10 (10%) rate of charge--Which exceeds the maximum charging current spec. for the GEL battery.

    At this point, we do not have an integrated charge controllers/battery monitors that can manage the measured current flow into a battery bank (Outback Flexmate capable?)--So it is difficult to use a GEL in a generic off grid power system.

    GELs can work great in UPS type applications where the battery is either charging (with charge controller output designed for C/20 rating), or AC mains have failed and batteries are supporting loads (no charging current available).

    At least how I look at/understand the situation for GELs and off grid power systems.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • SandyP
    SandyP Solar Expert Posts: 65 ✭✭
    #8
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    Re: found some gel cells for sale, your advice please

    Thanks Bill,
    Your input is appreciated as I have ony the manuals to rely on.
    It would appear that sulphation is less of a risk given the lower self discharge.

    The manual for my batteries indicates :

    2.4 Equalising charge
    Because it is possible to exceed the permitted
    load voltages, appropriate measures must be
    taken, e.g. disconnection of the load.
    An equalising charge is necessary after an
    exhaustive discharge and/or after an inadequate
    charge; it can be carried out at a constant
    voltage of max. 2.35 V/cell for up to
    48 hours. The end of equalising charge is reached
    when the electrolyte densities and cell (my comment : not sure why they refer to electrolyte densities as they are sealed)
    voltages no longer rise within a period of 2
    hours. The charging current should not exceed
    20 A per 100 Ah nominal capacity. Should the
    maximum temperature of 45°C be exceeded,
    the charging process must be interrupted or
    temporarily switched to float charge to allow
    the temperature to drop.

    and,

    2.6 Charging currents
    During continuous battery power supply or
    floating operation without a recharging stage,
    the charging currents are not limited. The
    charging current should lie between 10 A and
    20 A per 100 Ah nominal capacity (standard
    value).

    I understand the manuals reference to an "equalisation" is not that typical for FLA batteries however, the charging section seems to indicate these batteries can be charged at up to a 20% rate of charge?

    Given the information above, it appears that specific solar GEL batteries should be off grid suitable provided charging voltage is managed.

    In my case the cabin is not used frequently enough outside of the summer period and when it is the family are not up to speed with the maintenance needs of FLA batteries.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
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    Re: found some gel cells for sale, your advice please

    2.35v/c does equate to being an extended absorb charge.
    not sure what they are saying in section 2.6.
    20% is quite a high rate and even roughly equals other battery types for high current operations. maybe they have a radically different gel than other manufacturers have or maybe they prorate a degree of battery damage within the guarantee period that could mean the battery is destroyed soon after the warranty expires if maintaining the max charge rate of 20%. who knows? i would not take it out to the max and i'd wonder if even the 10% rate may also induce a degree of damages.

    in spite of the claims for your gels, i don't think gels are that well suited for solar applications and the manufacturer may just be pushing the envelope a bit to sell them.
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  • SandyP
    SandyP Solar Expert Posts: 65 ✭✭
    #10
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    Re: found some gel cells for sale, your advice please
    niel wrote: »
    maybe they have a radically different gel than other manufacturers have or,
    maybe they prorate a degree of battery damage within the guarantee period that could mean the battery is destroyed soon after the warranty expires if maintaining the max charge rate of 20%. who knows? i would not take it out to the max and i'd wonder if even the 10% rate may also induce a degree of damages.

    in spite of the claims for your gels, i don't think gels are that well suited for solar applications and the manufacturer may just be pushing the envelope a bit to sell them.

    Hi Niel,
    I cannot imagine a large company allowing for their batteries to continually fail based on planned obsolescence just outside of warranty - this is not a good business model.
    Is the reputaion for GEL batteries from the 2volt cells or peoples use of 12volt gel batteries?
    cheers.
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  • 65DegN
    65DegN Solar Expert Posts: 109 ✭✭
    #11
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    Re: found some gel cells for sale, your advice please

    I am always suspicious of used batteries and with a sealed battery it is difficult to impossible to reliably determine it's condition without doing an amp hour test.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #12
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    Re: found some gel cells for sale, your advice please
    SandyP wrote: »
    Is the reputaion for GEL batteries from the 2volt cells or peoples use of 12volt gel batteries?
    cheers.
    A large part of the bad reputation of GEL batteries among PV users is simply that they cannot tolerate a high rate of charge, making them unsuited for a situation in which they can only be recharged between 1 and 5 hours out of the day. If you try to charge them from a generator, the time limitation does not come into play, but you are inefficiently running the generator up to 24 hours per day!
    Niel is not saying that the manufacturer is pushing them in terms of warranty life. The manufacturer is pushing that they will be any good from the start if the user has to follow the charging current limits they set. For example, you could meet the charging current limits for GEL by installing a battery bank 4 times as large as the corresponding FLA or AGM. You would then end up paying 8 times as much for the bank as you would for FLA.
    SMA SB 3000, old BP panels.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #13
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    Re: found some gel cells for sale, your advice please

    to be honest i did open that possibility too of the manufacturer designing for failures just outside the warranty, but it was a passing thought and would be poor business practice to do if they want to continue doing business. as inetdog said you would need to get many more batteries to handle the charge/discharge cycle requirements posed by a solar setup compared to standard fla and agm types.

    also, i would reiterate coot's advice given in post 3. i will say if they are cheap enough and with good capacity that you may try them as your learning curve batteries. just don't have high expectations and if you get more than those expectations then great.
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  • SandyP
    SandyP Solar Expert Posts: 65 ✭✭
    #14
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    Re: found some gel cells for sale, your advice please
    inetdog wrote: »
    A large part of the bad reputation of GEL batteries among PV users is simply that they cannot tolerate a high rate of charge,

    Thanks for the feedback however, searching the NAWS and other forums the only references I can seem to find is people using low Ahr 12v GEL batteries in parallel nothing in relation to the 2v high amp hr cells - does this explain the issue of using batteries for what they are not designed?

    Can you point me in the direction of some info on issues with 2v Gel cells as I would like to avoid making mistakes others have already identified?
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #15
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    Re: found some gel cells for sale, your advice please
    SandyP wrote: »
    Thanks for the feedback however, searching the NAWS and other forums the only references I can seem to find is people using low Ahr 12v GEL batteries in parallel nothing in relation to the 2v high amp hr cells - does this explain the issue of using batteries for what they are not designed?

    Can you point me in the direction of some info on issues with 2v Gel cells as I would like to avoid making mistakes others have already identified?

    There is probably not as much information on forums about the 2volt GEL cells as the 12 volt, simply because they are less common.
    The problem with any GEL cell or battery, regardless of the voltage, is that if you charge it at high a rate the hydrogen and oxygen gas produced at the two electrodes will form bubbles in the gel material which will not recombine, leaving a permanent (or very long duration) void in the electrolyte and a loss in the capability of the battery. A secondary problem is that the cell has high internal resistance which makes it unsuitable for high discharge applications like driving an inverter.
    SMA SB 3000, old BP panels.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #16
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    Re: found some gel cells for sale, your advice please

    No battery expert--But I had read in places that GEL and AGM both have similar discharge characteristics (i.e., great for high current/short duration, such as for UPS / uninterrurptable power supply type operations). Just limit the charge rate to ~C/20 or 5% of rated AH capacity.

    Of course, different brands/models/construction of batteries will have different requirements.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #17
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    Re: found some gel cells for sale, your advice please

    For the OPzV cells with tubular plates, quite a few of them seem to have no current limit for bulk charging. They only mention limiting current above 2.25V per cell. E.g.:

    http://www.enersys-emea.com/reserve/pdf/EN-OPzV-PG-002_0111.pdf
    http://www.sonnenschein.org/PDF%20files/GelHandbookPart2.pdf
    http://www.elektrotec-berlin.de/download/hagen/eng/opzv.pdf
    And of course the Hoppecke's SandyP referenced.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #18
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    Re: found some gel cells for sale, your advice please
    stephendv wrote: »
    For the OPzV cells with tubular plates, quite a few of them seem to have no current limit for bulk charging. They only mention limiting current above 2.25V per cell. E.g.:

    Looks like these are not the same construction as the typical 12 volt GEL cells you see for use in alarm systems, etc.
    But even then:
    Important note : For all applications which use the PowerSafe® OPzV type battery in a cycling system,
    it is recommended that the technical department of EnerSys® should be contacted so that the technical parameters can be specified
    for the precise cycling programme in question.

    If you are confident in the reliability of the voltage settings (and temperature compensation) of your CC, then it may work out.
    SMA SB 3000, old BP panels.
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  • SandyP
    SandyP Solar Expert Posts: 65 ✭✭
    #19
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    Re: found some gel cells for sale, your advice please
    stephendv wrote: »
    For the OPzV cells with tubular plates, quite a few of them seem to have no current limit for bulk charging. They only mention limiting current above 2.25V per cell. E.g.:

    Thanks for the additional links to other manufacturers instructions - I found the Enersys document most interesting as it outlined more information on these types of batteries and assisted in decifering the Hoppecke user info that is somewhat technical (and maybe translated from German).
    Cheers.
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  • SandyP
    SandyP Solar Expert Posts: 65 ✭✭
    #20
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    Re: found some gel cells for sale, your advice please
    stephendv wrote: »
    For the OPzV cells with tubular plates, quite a few of them seem to have no current limit for bulk charging.

    Time to update the NAWS FAQ Battery page?
    Gelled electrolyte
    Gelled batteries, or "Gel Cells" contain acid that has been "gelled" by the addition of Silica Gel, turning the acid into a solid mass that looks like gooey Jell-O. The advantage of these batteries is that it is impossible to spill acid even if they are broken. However, there are several disadvantages. One is that they must be charged at a slower rate (C/20) to prevent excess gas from damaging the cells.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #21
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    Re: found some gel cells for sale, your advice please

    From their operation operation instructions:

    ...
    To reduce the recharging time a charging
    stage can be applied in which the charging
    voltage is max. 2.35 V x number of cells
    (stand-by parallel operation with recharging
    stage). Automatic changeover to the char-
    ging voltage of 2.25 V ± 1%
    ...

    2.6 Charging currents
    During continuous battery power supply or
    floating operation without a recharging stage,
    the charging currents are not limited. The
    charging current should lie between 10 A and
    20 A per 100 Ah nominal capacity (standard
    value).

    Interesting...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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