Modes of failure - batteries

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CALLD
CALLD Solar Expert Posts: 230 ✭✭
in Off Grid Solar & Battery Systems #1
Ok perhaps this thread applies to the hype and skeptic section somewhat, but I'm sort of more interested in predicting the exact way in which my batteries will one day kick-the-bucket.

I've seen many sales-type people talking about battery "life savers" and "desulfating smart chargers". I sort of doubt they would be of much use for a variety of reasons though.

Mostly because I'm not entirely sure sulfation is the only thing that is causing my batteries to age. I understand a lead acid battery is chemically reversible (recharging), but not physically. The plates warp and shed everytime they are cycled. Bits fall off and no longer form part of the battery. So whether or not getting sulfate off the plates is going to help, it cannot make an old and well used battery like new again.

So as enticing as these gadgets may be, I'm not sure it's worth the money...
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #2
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    Re: Modes of failure - batteries

    What do you have for batteries and how are they wired, series or parallel, and what voltage?
    How old are they?
    How heavily cycled on average each day?
    In the opinion of many people, including myself, the devices you mentioned tend to be nothing more than snake oil. That said, there are believers in political parties and religions of all stripes and the devices do make money for those selling them, so are therefore good for the economy.
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  • peakbagger
    peakbagger Solar Expert Posts: 341 ✭✭✭
    #3
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    Re: Modes of failure - batteries

    Batteries rarely die of old age, they are murdered.

    One of the main reasons why most off grid pros recommend going with cheap batteries for new off grid systems. The owner will inevitably kills them early and after writing a check several years earlier than expected, they start to treat the next set of batteries properly (or sell the house to some other newbie)
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  • CALLD
    CALLD Solar Expert Posts: 230 ✭✭
    #4
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    Re: Modes of failure - batteries

    Peakbagger: I hate having to agree with you, but that is pretty accurate. Even the worst kind of battery out there (the infamous SLI) can last for 10 years if used in the most appropriate way for it's design...

    But back to off-grid applications. My biggest mistake was choosing the wrong type of battery - the cheap and nasty stand-by type designed to spend years on float and only once in a blue moon be called upon to cycle. Then of course there's that big warning on the side of the battery that says "Must be fully recharged within 24 hours of discharge"

    Ok - now what about the real world where we live? It's fine to say that a battery must be fully recharged in 24 hours, but what if say we don't live in a place where the sun shines every day? Let's say you get a week of really bad weather? Your batteries could be hanging around 40-70% soc for that entire week! I know I'm hearing the word "generator" hammering against the side of my head but...
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #5
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    Re: Modes of failure - batteries
    CALLD wrote: »
    I know I'm hearing the word "generator" hammering against the side of my head but...

    But it might be cheaper to replace the batteries when they die young? Making a funny. But seriously, you are in a bind, a bind that thanks to the folks on this forum who guided me before I purchased batteries, I didn't end up in.
    I'd say you have a choice - - either a generator, as much as we may hate having to use them, and preparing now for the early purchase of a new set of batteries.
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  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    #6
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    Re: Modes of failure - batteries

    Just remember that solar charging is not perfect, although we strive to be.

    There are always some compromises one just has to accept, usually with shortened cycle life. Fortunately with the information here, you can cut down on the affect of those compromises.
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #7
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    Re: Modes of failure - batteries

    Actually you have a third choice: more pv.

    Pv is cheap, and long lasting. Batterys are neither.


    waynefromnscanada wrote: »
    But it might be cheaper to replace the batteries when they die young? Making a funny. But seriously, you are in a bind, a bind that thanks to the folks on this forum who guided me before I purchased batteries, I didn't end up in.
    I'd say you have a choice - - either a generator, as much as we may hate having to use them, and preparing now for the early purchase of a new set of batteries.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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  • CALLD
    CALLD Solar Expert Posts: 230 ✭✭
    #8
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    Re: Modes of failure - batteries
    zoneblue wrote: »
    Actually you have a third choice: more pv.

    Pv is cheap, and long lasting. Batterys are neither.

    That is something I have considered, along with the realization that the weather in PE is a lot more cloudy than I thought before deciding to go with solar....

    I'm seriously considering deep cycle GEL/AGM batteries because I've stumbled across a relatively cheap source. They promise at least 900 cycles to 50% DOD vs the 250cycles my current set promise. What attracts me to these GEL batteries over flooded is the shorter charging times, lower charging voltage & higher discharge voltages. When the sun is as intermittent as it is here it seems better to have more PV and batteries that can soak up the available power quicker.

    I have the worst possible combination right now: batteries that require high charge voltage with a long absorb stage, too little PV and very intermittent sun...
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
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    Re: Modes of failure - batteries
    CALLD wrote: »
    That is something I have considered, along with the realization that the weather in PE is a lot more cloudy than I thought before deciding to go with solar....

    I'm seriously considering deep cycle GEL/AGM batteries because I've stumbled across a relatively cheap source. They promise at least 900 cycles to 50% DOD vs the 250cycles my current set promise. What attracts me to these GEL batteries over flooded is the shorter charging times, lower charging voltage & higher discharge voltages. When the sun is as intermittent as it is here it seems better to have more PV and batteries that can soak up the available power quicker.

    I have the worst possible combination right now: batteries that require high charge voltage with a long absorb stage, too little PV and very intermittent sun...

    Do not make a second battery mistake. GEL batteries are not suitable for RE use (with a few exceptions). 900 cycles is about half what a set of inexpensive flooded cells will do. The "lower charging Voltage" of the GEL is another way of saying "easy to fry". By the same token, avoid those flooded cells which require high Absorb Voltage (Trojan & Surrette to name two).

    When your location has low insolation you either buy more PV or run the generator.
    Or realize that solar makes no sense under such circumstances.
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #10
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    Re: Modes of failure - batteries

    The established forum wisdom is GC2s for smaller systems. Why does everyone have this burning desire to cut corners, and reinvent the wheel.?
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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  • Alaska Man
    Alaska Man Solar Expert Posts: 252 ✭✭
    #11
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    Re: Modes of failure - batteries

    My AGM's ROCK!! I love that I can pour the hydrocarbons into them and get to 90% SOC in under an hour most days. I also have come to the realization that 95% of the time I will run my generator for an hour every morning sun or no sun.

    So far my off-grid education has taught me; Nothing is ever as good as you think it will be or as bad. ;-)
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #12
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    Re: Modes of failure - batteries

    Using Solarelectrichandbook, fixed array:

    Port Elizabeth
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 56° angle (from vertical):
    (For best year-round performance)

    Jan
    Feb
    Mar
    Apr
    May
    Jun


    6.09
    5.78
    5.38
    5.03
    4.66
    4.46



    Jul
    Aug
    Sep
    Oct
    Nov
    Dec


    4.74
    4.99
    5.39
    5.45
    5.80
    6.10


    Looks like, on average, pretty sunny there (not to argue with the guy that lives there :roll:).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    #13
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    Re: Modes of failure - batteries
    CALLD wrote: »
    I'm seriously considering deep cycle GEL/AGM batteries because I've stumbled across a relatively cheap source. They promise at least 900 cycles to 50% DOD vs the 250cycles my current set promise. What attracts me to these GEL batteries over flooded is the shorter charging times, lower charging voltage & higher discharge voltages. When the sun is as intermittent as it is here it seems better to have more PV and batteries that can soak up the available power quicker.

    Just be sure you know the difference between Gel and AGM. Notably, gel requires a lower charging voltage, such as no more than 14.1v, whereas AGM's can vary from 14.4 to 14.8 or so. Frying a gel is done by not knowing this, and treating them as "drop-in" replacements for agm or even flooded without changing your charging voltage. But there is another catch.

    Most generic gels will not accept any charge current higher than C/20. One exception is MK-Gel.

    Most general purpose lead-calcium agm's recommend no more than C/3 to C/4. This is good, but of course means you need more panel power if you want to go there. East-Penn / Deka recommends getting as close to C/3 for longest life.

    Higher end AGM's, such as Enersys (Odyssey) / Concord, and even Optima have much lower internal resistance, and can accept even higher charge rates. Of course, that means more panel power. But, take a look at the cycle life and see if the higher cost justifies the cycle-life ratings. It might if you are in a bad solar-insolation condition and have the panel power to charge in a short amount of time.

    Just don't jump into some new batteries too quickly without taking time to research your needs. For example, you may simply wish to change out a set of common GC-2's more often, than buying into expensive high-end agm's. BUT your loads and solar-insolation conditions may demand that. Those in the Pacific-Northwest and other low insolation areas pay much more for an off-grid system due to this.

    Be sure to see the NREL solar-insolation charts, along with all the good advice.
    http://www.solar-electric.com/solar-insolation-maps.html/

    Basically, lock up your wallet tight before jumping.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #14
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    Re: Modes of failure - batteries

    Trojan T-105's have a known and touted average cycle life of 700 cycles @ 50 % dod. They use to be a deal when you could buy them for $50, now at $149 msrp ( if you can find them $90 + they are still a deal ), not so much. Shipping cost is almost prohibitive on batteries, check golf cart shops and Golf Courses for them, this time of year there are deals to be had.

    Interstates and others fall somewhere in the middle. The Sams / Costco GC-2's would be somewhat lower , but for $84 they still become a deal. They will easy go 450-500 cycles @ 50 %. I'd say most GC-2's die of old age at the 4-5 year level from my experience, with a odd bank going 6 years. Sitting around on Float forever is not much of a life for a Battery.

    GC-2's require nothing exotic, they charge easy and are predictable. Give them water every couple months and check the SG level and they are happy with short absorbs.
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  • CALLD
    CALLD Solar Expert Posts: 230 ✭✭
    #15
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    Re: Modes of failure - batteries

    Correction - they are not GEL, seem to be VRLA AGM. the batteries I'm looking at getting are two of these:

    http://www.sustainable.co.za/media/pdf/SonX%2012V260Ah(D).pdf

    They are considerably cheaper than flooded here in SA. See Price comparison:

    http://www.sustainable.co.za/solar-power/solar-storage-batteries.html?amphours=252
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  • CALLD
    CALLD Solar Expert Posts: 230 ✭✭
    #16
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    Re: Modes of failure - batteries
    BB. wrote: »
    Using Solarelectrichandbook, fixed array:

    Port Elizabeth
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 56° angle (from vertical):
    (For best year-round performance)

    Jan
    Feb
    Mar
    Apr
    May
    Jun


    6.09
    5.78
    5.38
    5.03
    4.66
    4.46



    Jul
    Aug
    Sep
    Oct
    Nov
    Dec


    4.74
    4.99
    5.39
    5.45
    5.80
    6.10


    Looks like, on average, pretty sunny there (not to argue with the guy that lives there :roll:).

    -Bill

    Haha yes I got excited too when I looked at those figures for the first time... Trouble is I think that data is pre-climate change!

    For the last two years I've been noticing that spring is becoming gloomier and winter brighter. Seasonal lag now seems to be much longer as it can feel like winter right up until December and feel like summer well into June.

    Before getting solar panels I remember unbroken sunshine for weeks upon weeks, worrying about the plants in the garden and sky-high water usage. Since getting my solar panels the un-obscured sun seems to have become a rare occurrence...
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  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    #17
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    Re: Modes of failure - batteries
    CALLD wrote: »
    Correction - they are not GEL, seem to be VRLA AGM. the batteries I'm looking at getting are two of these:

    Right. Those are conventional lead-calcium agm's, which are recommended in the charts to be charged at no higher than 0.3C. That means no more than about 78A for that size.

    Also look at the DOD / Cycle life chart. About 750 cycles at 50% DOD - or a little more than 2 years of daily cycling before they reach a 20% decline in capacity. Pretty typical.

    Of course real-world may differ plus or minus as compared to just bench-racing the specs.
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  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    #18
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    Re: Modes of failure - batteries
    Blackcherry04 wrote: »
    Tcheck golf cart shops and Golf Courses for them, this time of year there are deals to be had.

    I snuck into deals on GC-2s 130Ah 6 v Industrial from many ritzy Golf clubs , one year to two year old battery's in the fall they pull & clean service them till next year & install new Battery's . These dudes who whack little white balls over a imminence green&blue ball , have rented these 1/2 used packs. Im getting them for over scrap of 25-30 bux each . all test as 12.6 / 75 SG each . Spend most of the time in charge , But if one dyes on the course , these white ball whackers go crackers !!!

    This is YVR SEA Area ..

    VT
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #19
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    Re: Modes of failure - batteries

    Yeah 0.3C, you hear that. But what do you say to this

    http://www.powerstream.com/SLA-fast-charge.htm



    PNjunction wrote: »
    Right. Those are conventional lead-calcium agm's, which are recommended in the charts to be charged at no higher than 0.3C. That means no more than about 78A for that size.

    Also look at the DOD / Cycle life chart. About 750 cycles at 50% DOD - or a little more than 2 years of daily cycling before they reach a 20% decline in capacity. Pretty typical.

    Of course real-world may differ plus or minus as compared to just bench-racing the specs.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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  • CALLD
    CALLD Solar Expert Posts: 230 ✭✭
    #20
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    Re: Modes of failure - batteries

    Ok, took delivery of my new 260Ah VRLA AGM's yesterday:) My mind was pretty much made up on them several months ago due to the prohibitively high price of good FLA deep cycle batteries here in SA. The zero maintenance factor and no need for messy SG checking was also a big factor. The fact that they would need to be replaced every few years or so is not too much of a problem as I expect technology to bring something new and exciting in the mean time.

    The results have been simply amazing so far!

    Voltage comparison on exactly the same daily loads are as follows:

    My old 306Ah Ag/Ca bank:

    18:00 - 25.8v
    19:00 - 25.1v
    20:00 - 24.6v
    21:00 - 24.2v
    22:00 - 23.8v
    06:00 - 23.5v

    My new 260Ah AGM bank:

    18:00 - 25.6v
    19:00 - 25.4v
    20:00 - 25.1v
    21:00 - 25.0v
    22:00 - 25.0v
    06:00 - 24.8v

    To this day I have no idea why the old AG/CA batteries were performing so badly, other than the possibility that they were nothing more than SLI batteries dressed up in fancy looking stickers that claimed more than they were capable of... They didn't even show much of a decline in performance in the 5 months that I was running them. Those figures were similar they day I hooked them up. They seemed to lack stamina or something. I put them all on one of those CCA load testers mechanics use after removing them from my system and they all tested "Good". Mystery to me, but will not shed a single tear. Will charge them up and sell em off...

    Otherwise I'm feeling very positive about my new set:)
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #21
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    Re: Modes of failure - batteries

    Thats getting carried away. Any battery that costs a lot, doenst last long and is virtually impossible to know if youre charging it correctly, is hard to get excited about. Sure lower internal resistance is nice, but thats their only real redeeming quality... applicable to RE users anyway.

    Alaska Man wrote: »
    My AGM's ROCK!! I love that I can pour the hydrocarbons into them and get to 90% SOC in under an hour most days. I also have come to the realization that 95% of the time I will run my generator for an hour every morning sun or no sun.

    So far my off-grid education has taught me; Nothing is ever as good as you think it will be or as bad. ;-)
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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  • CALLD
    CALLD Solar Expert Posts: 230 ✭✭
    #22
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    Re: Modes of failure - batteries
    zoneblue wrote: »
    Thats getting carried away. Any battery that costs a lot, doenst last long and is virtually impossible to know if youre charging it correctly, is hard to get excited about. Sure lower internal resistance is nice, but thats their only real redeeming quality... applicable to RE users anyway.

    Here in SA industrial grade flooded batteries or 2v cells are a lot more expensive per C/20 Ah than the AGM's I just bought.
    24v 260ah AGM, 800 cycles to 50% expected = $800
    24v 260ah industrial FLA 2000 cycles to 50% expected = $2000 or more!

    Price per AH cycle is identical.

    AGM's lower internal resistance means you get more power for what you put in due to the smaller voltage difference between charge and discharge. Absorb times are much less too. All in all it makes your off grid setup more energy efficient.

    Yes I do concede they are less tolerant to charging abuse, but that's what charge controllers are there to prevent right?

    AGM = no working with dangerous acid while taking SG readings, no topping up, no stratification. Less maintenance = less stress and anxiety and more sleep at night. Just watch the voltage and battery temperature, that's all...
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  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    #23
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    Re: Modes of failure - batteries
    zoneblue wrote: »
    Yeah 0.3C, you hear that. But what do you say to this

    http://www.powerstream.com/SLA-fast-charge.htm

    I was excited about that too many years ago. Oh sure, you can do it, but what they don't mention is the hit you take on cycle life for batteries not intended to do that repeatedly. What also occurs are "hot spots", which are harbingers of thermal runaway, even if the charge time is short. Eventually it catches up to you. Or your application is so non-critical that you just are willing to eat the cost of batteries.

    I took my handheld IR meter, and abused some new Powersonics in precisely this manner to witness the hotspots getting created. So yes, it can be done, but it will cost you! Not only that, but you don't really achieve a full charge due to Peukert. Welcome to partial-state-of-charge operations, where eventually you need to actually do a full charge at the normal rate.

    Over 0.3C can be done, but that takes agm's designed to handle very high charge / discharge currents, and that is usually Enersys, Concord, Optima etc.

    I performed this test by hammering little Enersys "Cyclon" 5ah cells with 10ah. Over and over. No hot-spots. Designed to take it.
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  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    #24
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    Re: Modes of failure - batteries
    CALLD wrote: »
    Yes I do concede they are less tolerant to charging abuse, but that's what charge controllers are there to prevent right?

    That's right. Smart users dont' just treat all batteries as drop-in's for another and choose their voltages correctly.

    I am still a big agm fan. In fact, the high-end agm's response to solar is what prompted me to move to the next logical step - lifepo4. However, like all batteries, there are tradeoffs, and there is no "pat" answer. You decide what is important, and what is not and what you'll tolerate. Some enjoy reading flooded SG's with a hydrometer. Others are willing not to be able to do so in order to have much lower internal resistance, ability to be charged at 0.3C and higher if allowed and so forth.

    The biggest thing to take away from this is that batteries have different requirements, needs, and owners. Neither is "superior" to another and shouldn't be seen as some sort of attack on those not using the same chemistry.
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  • CALLD
    CALLD Solar Expert Posts: 230 ✭✭
    #25
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    Re: Modes of failure - batteries
    PNjunction wrote: »
    I am still a big agm fan. In fact, the high-end agm's response to solar is what prompted me to move to the next logical step - lifepo4.

    I must say I'm falling more in love with my AGM's each day - the correlation between voltage and SOC seems to be so accurate its a walk in the park determining SOC, All I do is walk over to the charge controller, glance at the voltage and the load and I know exactly how much is left in the battery. There's no polarization to speak of, only the very marginal load-induced voltage sag to take into account.

    I do dream of LiFePo4 batteries, as well as the hyped-up "Lead Crystal", but at current local prices I will wait until my knowledge has grown enough to make a big decision like that.

    For now, loving my AGM's, trying to find a buyer for my old half-used Silver Calciums (Although I wouldn't be surprised if there aren't any takers). Perhaps I'll just experiment on them or use them as a mobile welding power supply.....
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