GBS LiFePo4 20 and 40ah batts

2

Comments

  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    I think I found my perfect charge controller for lifepo4, which really isn't a charge controller at all just a programmable switch! YES! Stay out of the way, and just switch on and off at the presets I want.

    Sterling ProLatch-R

    I'll set the HVD to 13.8v
    I'll set the LVD to 12.5v

    Done. I'll report back when the budget recovers from my multimeter frenzy. LiFePo4 does not have to be difficult!
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    Solar design notes ....

    No matter the chemistry, we generally design a system around a 50% DOD to allow for a bit of autonomy or the unexpected, and in the case of lead, is conveniently the tipping point between usability and cycle life. And with lead, this usually means thinking in terms of 0-50% DOD, or starting from a "full charge".

    Lifepo4 can turn that thinking around a little bit. Since there is no need to obtain a 100% full charge to get the cycle life out of it, you can let that 50% window slide and not be penalized. This affords you some headroom, which is one of the basic tenets of doing solar. We are dealing with a chemistry that has no sulphation issues , so partial state of charge operations are no problem.

    The question from an operational standpoint for lifepo4 would be, "what is a full charge?"
    The answer would be "enough to satisfy your capacity needs without hitting the LVD regularly."

    For example, lets say you start out doing the 0-50% DOD routine because you are so accustomed to doing this with lead, but due to a temporary unexpected load, or temporary poor solar insolation, you now suddenly find yourself operating from 10-60% DOD regularly. This is not a problem. How about 20-70% DOD? Again, not an issue. Even 30-80% will not hurt. Not to mention that operationally, you won't notice it much since Peukert is super low.

    Try taking a lead-acid battery from 30-80% on a daily basis and see how long it lasts, providing your gear will actually operate efficiently beyond say 60% DOD.

    But yes, like any battery the deeper you discharge the less cycles you will obtain. However, from the manufacturer spec sheets, we see 1500 or more cycles when operated under their typically higher-than-necessary specifications, so pampering them like we do in a storage application means much less worry about it. Nobody yet has put any numbers to psoc cycle life, but I'm not going to sweat the difference if that means only a 3-month difference in the long run. :)

    So while one should plan a solar system properly, with lifepo4 that does NOT mean you must think in terms from 0-50% DOD. Didn't hit your high voltage setpoint today? Don't sweat it, as long as you didn't undersize your bank to begin with.

    That brings up a very big temptation with lifepo4 - designing your system to take advantage of the fact we can REALLY go down to 80% DOD and not suffer like we would with lead. With solar, that would be foolish to skirt the edge like that so don't be tempted to under-size your bank.

    WARNING - anyone who actually tries to do accellerated psoc type testing must NOT FORGET to allow for at least 1 hour rest periods between charge / discharge. This isn't specific to lifepo4, but to any battery chemistry undergoing this kind of rapid cyclic abuse in an automated setup. And of course like Prof J. Dahn likes to point out, is not realistic. To do it right, you'd only do one cycle a day, along with recording all the temperatures, and show your results in about 8 years. See ya then. :) Or take your batteries to Dalhousie University and put it on their advanced testing setup if you don't have 8 years, and need more accurate and much quicker results than simple rapid-cycling abuse can provide.

    https://www.youtube.com/watch?v=9qi03QawZEk

    Although it starts with the typical EV issues, remember that we are pampering ours with a storage application, but most of it is still applicable.

    One aspect is that the higher in voltage you charge to, perhaps by constantly running external high voltage balancing bleed off boards, you increase electrolyte oxidation, coating the negative, and eventually shutting the cell down prematurely. You'll be frustrated when you discard your perfectly balanced cells sooner than expected. :)

    The KISS method I use for balancing, and not running to extremes is a very good idea I believe.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    YAMMU - Yet Another Multi-Meter Update

    Got the Fluke 116 today which does temperature with supplied probe. MUCH better than the RS outdoor thermometer! Surprisingly, the RS thermometer was only about 3 degrees higher than the fluke, ie 105F vs 102F on the Fluke when I was charging the GBS cells in the shade. Guess which one I trust? (yeah, the probe itself could be off a little too - I might upgrade later)

    One factor I overlooked was the SPEED in which the Fluke operates. The RS meter takes anywhere from 10-15 minutes to go from about 85F to 105F. The fluke gets the measurement from that spread in a minute or two. Speed might not seem important initially, but these lifepo4's have much less mass than lead acid, and therefore acclimate to the environment much quicker. If I'm skirting the ambient or cell-skin / bus temperature specs, I've got to know fast, not in 15 minutes. Right on Fluke.

    Why didn't I just use my 87V for this initially? I lost the temp probe that came with it. And it is not intended to be my 100F+ outdoor beater/monitor.

    For lifepo4, inexpensive yet accurate-enough trust I place in the Fluke 11x series. However, I would not go below the 114 model. For just doing voltage monitoring, I thought about the 113, but that does not have the resolution you need in the display. Since the 113 only operates in the "low Z" mode, I placed the 116 in that mode too, and discovered the limitation in low-z to the tune of guessing about 50 millivolts or more either way. In addition to that, since low-z is primarily used for electrical, and not electronics work, if you use a 113 for electronics, the low-z may load down your circuit and give you the wrong values.

    The spare 115 will be primarily used now to keep an eye on overall bank voltage when it is indoors. This is certainly better than hobbiest RC-modeler monitors. Instead of constantly rotating the switch when I want to take a look, I'll just leave it in the dc volts position and let it time out. Just a tap of a button will bring it back to life from the sleep mode. If I really want to, I could disable sleep altogether and just go through batteries. I'm covered here as well by using a rechargeable Maha Imedion 8.4v low-self-discharge battery, (not the regular yellow/white ones) and a Maha Powerex MH-C490F charger to make sure the charge is done right. I'm NOT using the 9.6v Imedions, as they have too high an soc voltage at full charge. (A misnomer for the 9V "standard" is that there really is none!) If for nothing else, I'm not going to let an alkaline live in my Fluke's, despite the common view that alkalines don't leak - they have on me, and the rechargeables if charged properly, don't.

    Yep, I'm a battery geek, but I'm trying to simplify, rather than make things more complex than they need be, despite this long review.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    KISS works!

    While waiting for my Sterling Prolatch-R to arrive, I decided to become the latch myself and charge directly from a panel. (NOT RECOMMENDED for Normal Use!!)

    Armed with 3 Flukes, a 60w panel, the 20ah battery, 2 cool non-alcoholic drinks, a lawnchair, and a whole lot of ridicule from the household, I set about charging in 100F, and near perfect solar insolation conditions.

    To make a long story short, the battery just gobbled up all it could as fast as it could, and of course, wanted to make itself rise to meet the 18v of the solar panel, so I cut it off manually once it reached about 13.8v. All cells were within balance and showed no signs of straying from what they were when I first did the balance.

    Not surprisingly, my discharge test easily met the 80% DOD specification, once reaching 12.8v under load. I let it go further down to 12.5v under load, roughly 90% DOD or so, and that is my personal hard limit. Too many EV'ers and others take it well beyond this, which I'm not comfortable with and see no need for, since you already got what you paid for. I try not to take it below 12.8v under load as a normal rule.

    So here again, lifepo4 does not need complexity. A simple smart relay (draws very little current during use) that trips at 13.8v without waiting for any sort of absorb or end-amps, works just fine since you are staying within the knees.

    95% SOC is the new 100! :)

    I just don't get it. Lifepo4 prismatics are nearly the perfect battery for solar, and if you don't take it to extremes, you can keep things very simple. In fact, I view it as easier to maintain than even an AGM. For some, simplicity means that there is something wrong, but in this case, no. Either way, you can easily prove it to yourself and see if you would feel more comfortable with more complexity.

    Feeling kind of smug and rebellious. If there ever was a theme song for lifepo4 that came from my era, it would Pushin Too Hard by the Seeds. The MAN wants me to slap all sorts of external junk over my simple 4S battery. I don't think so! :)
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    PN, Is there a typo?


    I stopped it just before reaching 12.5v under load. 12.8v under ( NO? ) load met the spec already.
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    No typo, but it is worded badly. I'll fix that so thanks for the heads up.

    I was discharging, and when it reached 12.8v, I was already at 80% DOD, as measured with a CBA-IV, so I let it go a little bit further, and stopped at 12.5v under load as my hard limit. Cells were still balanced at that point. Of course the CBA-IV could be out of spec, but so far it seems to be close.

    Looking at the Prolatch-R manual, I'm a little scared, so that will be an interesting challenge to make sure I get the settings right. At this stage, I'm not sure a single unit can perform both an HVD and an LVD the way I want to, but we'll see ...
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    You know, I'm not going to hold it against anybody if they feel that they need to put those cell balancing boards across their cells, and run their chargers up to 14.4v, and let the little boards do their thing after a few cycles.

    There is no law that says you have to keep them installed either! Once you are satisfied that they have done their job, you can just as easily remove them, and then lower the voltage on your charger / solar cc to 13.8v and live happily ever after too. I just preferred to do it manually.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    DISPOSAL issues ...

    If for some reason you decide to dispose of your battery bank, then the nice thing to do is to fully discharge them before putting them into the hands of the recyclers, or other handlers on their way to the dump. If you really want to take them down low just put a vehicle headlight bulb across each cell. The bulb voltage doesn't really matter. MARK them as BAD. There is a little bit of plastic, aluminum and copper to reclaim from them, although some recyclers may not be set up for lifepo4 recycling.

    The reason for marking them as BAD is you don't want somebody finding these totally discharged cells and trying to recharge them again as they are already damaged goods at that point.

    If you have damaged your cells, and they show the classic signs of abuse like swelling, (like applying a normal current charge to totally discharged cells!) just discharge them down before discarding them. Fix your charging setup before using new cells, and perhaps seek another distributor who isn't pawning off used cells where you have no idea of their history. Used cells are NOT a bargain for this very reason.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    Another call for lowering your charge controller voltages to no more than 3.45v per cell (13.8v for nominal 12v bank), ...

    It has to do with TIME exposure. Brief excursions into the upper and lower knees will not immediately render your bank unusable - at least within the safe voltage ranges. It doesn't mean it is optimum of course, but won't do immediate damage if the time is limited.

    What you want to avoid is using an under-powered solar array spending a lot of time trying to reach a goal that takes too long at the upper voltage ranges, ie higher than 3.45v per cell. For instance, if you have your voltage set to 3.6v per cell (14.4 for nominal 12v bank), you may never actually reach it with an unstable source like solar, BUT you may hover slightly below for days on end, which is not good!

    Another example: You have an 800ah bank, but choose to initially charge each cell with a 2A individual cell charger rated to go to 3.7v. Despite lifepo4's fantastic CAR, you will spend waaaay too much time getting there, even at relatively high levels of SOC when starting out. Trying to squeeze the last drop of blood from these things with an underpowered array is only giving more time for the higher-voltage parasitic reactions to occur.

    Yet another example - your cells have the balancing boards on them which want to see 3.6v per cell (14.4v on nominal 12v batt) before they start doing their passive bleed-off balance. You are charging with an undersized solar panel or have poor conditions, and the cells never actually reach 3.6v - ever, but they do reach slightly below and live there forever. Not only are you not balancing, you are accumulating the parasitic affects of living in the upper charge knee, but never quite reaching the set voltage. In this case, either use an ac powered charger to do the job and get it over with and remove the boards after you are satisfied that the balance has been achieved - and drop your voltage to 3.45v for use with solar. Or, do it manually like I do and get the balance issue right from the start without using boards. Typically no more than 0.050v (50 millivolt) spread after a 2 hour or longer wait - covered earlier ...

    Solution - 3.45v per cell. That covers the possibility that you may have undersized your array, or are experiencing long periods of poor solar insolation, but just bad enough to make the battery live in the upper charge knee for a long long time. By not setting your CC voltage beyond the start of the charge knee, you are covered. In fact, if you weren't doing any cyclic duty at all, I'd limit it to 3.4v per cell, but my interest is not using lifepo4 as a standby application.

    Yes, I take mine to 3.5v (14.0 on my Samlex charger), on my smaller batteries, but it doesn't spend much time there before the charger shuts off.

    So if you don't have the luxury of a big array to get the charge completed and shut off, or have questionable solar insolation, the safest bet is to just set for 3.45v per cell.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    The Sterling 80a Prolatch-R arrived!

    Gulp. It will take a few days to become "one" with the manual, so stay tuned. If I feel like I'm in over my head, sticking to the Xantrex pwm controller set for 13.8v will do. :)
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    Back to the Xantrex!

    The Sterling Prolatch-R seems like a fine piece of equipment, but the user-interface of magnetic swiping, counting led flashes, temporary jumpering for programming leaves me a bit cold. Not only that, but to prevent the relay from chattering, the voltage settings aren't instantaneous, but have a timed algorithm from a few seconds to many minutes. With Lifepo4, those minutes could be crucial. I read the manual before purchase, but once I got it into my hands, I saw what I was in for. I'll save it for another project.

    The Schneider/Xantrex C12 will remain set for 13.8v for both absorb and float for fixed operations. For my temporary portable use, I think I'll do a small tweak like setting the absorb to 13.9v, yet still leaving the float at 13.8 to see if that will have a little less of a heavy-handed pwm approach during bulk charge, but still provide a margin of safety.

    I'm only setting the float to 13.8 because of the 1 hour time limit in absorb, which drops out too early on the Xantrex, so these tweaks are not meant to optimize voltages, but to beat the clock - at least until the sun goes down and there is no float at all! :)
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    Another place for GBS batteries - electricmotorsport

    Sometimes it is hard to find the smaller 20ah batteries if you want to just get your feet wet. Electricmotorsport seems to carry the whole line, but most importantly even the smallest 4S-prismatic 20ah GBS LFMP20AH, which I started with (although I got it elsewhere). It resembles the size and weight of a 12-18ah agm, but in operation can be loosely compared to an Optima D51 operationally given the differences in DOD capability.

    Tie this into your Pb charge controller set for no more than 14.v (typically gel settings), and just make sure that no cell goes over 3.6v before reaching a pack voltage of 13.8v and you should be set, unless you want to go nutzo over top-balancing. Don't take it below 12.5v, preferably a little higher like 12.8v and you'll be set. A Samlex SEC-1215UL ac charger toggle switched to 14v works fantastic too.

    That's about as KISS as you can get.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    Very interesting thread which seems to be missing one point: cost?

    Because of a discussion in another thread I'd like to see if we can quantify the value of the LiFePo to FLA's. I realize the convenience of flexible charging can't reasonably be factored in.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    Re: Cost

    Ok fair enough, but the comparison to either FLA or AGM isn't really a straight-across capacity / vs price comparison, but here we go ...

    Since a lifepo4 can run 1500 cycles down to 80% DOD, how many *RE DEEP CYCLE* FLA's or AGM replacements would it cost to provide the same amount of power? I suppose that to approach 1500 cycles with fla or agm, that means never going past 50% DOD. Let's assume we are not talking Costco cheapies, but true RE batteries. Another reason for not going past 50% DOD with the comparison to FLA is that lifepo4 has an extremely minimal peukert. Try taking a Pb down past 60% and operationally you are in trouble. Lifepo4 - no problem. So there are other factors, but I'll leave it at that.

    I'm not up on my FLA pricing, so I'll have to leave it to others to do the math, but the max DOD differences between FLA/AGM and Lifepo4 needs to be taken into account, which basically means that lifepo4 emulates a much larger fla battery.

    But very simplistically, my $125 20ah GBS lifepo4 (at 80% DOD) would operationally on a single-day basis, would be the rough equivalent to a larger Concord Sun-Xtender PVX340T AGM (at 50% DOD max) at what, $125. About the same!

    My $240 GBS battery at 40ah (32ah at 80% DOD) would compare to a $215 64ah PVX-690T SunXtender at 50% DOD. Ok, a little more. As we move up in lifepo4 capacity, the disparity starts to grow a little larger each time....

    But everyone likes to point out that over time, the lifepo4 cycle life means more bang for the buck. And even more the way WE treat them, which is nicely. If you don't take them down to 80%, but just to 70% DOD, or run in a PSOC style of operation, then predictions are 3000 cycles or so - but I haven't personally run across anyone who has been through 3K cycles yet.

    So I'll leave it at that point, unless one wants to take into account the operational / charging aspects too, like minimal absorb, which means less fuel when running a genny since one is nearly always in bulk charge efficiency. There is a lot more, but I'll stop since this appears to be an upfront cost vs cycle life issue.

    Maybe this helps - the real battery experts like you guys will certainly be able to get to a more realistic standpoint than I can, because my hands on with true RE fla batteries is very limited.

    While a cost comparison between FLA and Lifepo4 would be interesting, without taking into account the operational strengths of each, and the needs of the owner, it may be a mere data point. For instance, since I don't have the time to properly maintain an FLA with proper EQ's on a timely and regular basis, that alone is saving me money by going with lifepo4 since I won't be killing a nice RE fla prematurely. :)
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    Maybe this will explain why I think a straight-across price/capacity comparison is unfair to either fla or lifepo4 - the chemical and operational differences are like comparing apples to oranges.

    https://www.youtube.com/watch?v=oJ8AfJsOhsM

    Here the guy is doing a constant draw of about 0.25C on his 400ah bank. That's not me, and I do NOT run a rat's nest of bms wiring over the top of it. He took it waaay too far and very close to the edge for my tastes, but he did so on purpose.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    Difference in DOD is an adjustment in capacity: usable Watt hours. We do this for forklift batteries for example: 100 Amp hours of forklift is 80 usable Amp hours whereas you need 160 in standard deep cycles to have the equivalent amount of power.

    This has to be balanced against predicted cycle life, which comes up against the reluctance of manufacturers to put a number on that (or at least release it to the public). But if the cycle life were 1500 in both cases it would be as direct a comparison as possible.

    So subbing LiFePo for forklift you get the 1.6 ratio in capacity to correct pricing. And of course you need equivalent pricing.

    Thus 40 Amp hours of LiFePo is equal to 64 Amp hours of FLA. Or 220 Amp hours of FLA can be made up by 137.5 Amp hours of LiFePo. Never going to find an exact match of course. But that much LiFePo @ $250 per 40 Amp hours would be $860? Pretty far off from a couple of GC2's @ $266 for name-brand, never mind warehouse.

    I think that will stop most people from investigating LiFePo any further. It is hard to put a dollar value on the charge state flexibility (which is better for RE*) and there's no guarantee on cycle life either. If it were closer in price more people would be interested.

    Anyone else who has a take on this aspect feel free to express it as this is a promising battery technology.

    *On cloudy days an RE system may experience charge/drop/charge which for the battery life amounts to another cycle. This is also true of the use of generator at night to boost after a solar charge during the day. These extra cycle demands are impossible to predict but do affect lifespan; the LiFePo does not suffer from this effect as it has high partial SOC tolerance (and even preference). It is also debatable how much affect these 'mini cycles' have on standard RE batteries. Long-term performance in a side-by-side comparison would be needed to achieve any worthwhile data on this. Anyone want to put up the money? :D
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts
    PNjunction wrote: »
    Re: Cost

    But everyone likes to point out that over time, the lifepo4 cycle life means more bang for the buck. And even more the way WE treat them, which is nicely. If you don't take them down to 80%, but just to 70% DOD, or run in a PSOC style of operation, then predictions are 3000 cycles or so - but I haven't personally run across anyone who has been through 3K cycles yet.
    :)

    The thought just occurred to me that one wold need to know the test parameters of those FLAs and LiFe batteries to get a close-to-reality check on comparing the 2... I would bet that the "cycles" advertised are achieved with a real whopping big (max?) load on either battery type and then the fastest recharge they can do.... otherwise a 3000 cycle test would take ~10 years,...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    We can get the specs direct from the factory for GBS here, as seen in their 100ah battery:

    http://www.gbsystem.com/products-show-en.asp?id=78

    We've got about 2000 cycles at 80% DOD, BUT at what I consider at the extreme edges of charge discharge voltages, which I will never go to! Like you say, this is on paper, but most of the posers in the last 5 years have fallen by the wayside, leaving GBS, CALB and some others in the game.

    Prices are falling, but the review was not really intended to try and sway people away from their favorite chemistries, but to dispel some of the myths about the seeming complexity of charging lifepo4. I think these will appeal to those who use AGM, rather than FLA as their storage batteries.

    Consider the Concord SunXtender agm is only rated to go 1000 cycles at 50% DOD. The GBS cells are 2000 at 80% and at those extreme voltages.

    If cycle life vs the *current* price is your only criteria, then yes by all means keep on waiting and stick with what you are comfortable with.

    But if light weight, no sulfation, no temp-comp, no EQ, no need to reach 100% SOC EVER, practically no peukert, no absorb to speak of when using a genny, simplified charging algo, and up to 1C charge/discharge if necessary fits into your solar situation then you may want to look seriously at lifepo4.

    Consider this - the "too small a panel for too large a battery" syndrome is not a problem for those who make a mistake, and of course still have enough capacity not to kill it. On the other hand, the reverse can be true for those that go too large with their array - the lifepo4 will take 1C handily. Or the weekend warrior that visits the cabin only on the weekends, and takes all week to charge - no sulfation, no problem if that week turns into two months of bad weather - the lifepo4 won't sulfate while discharged in the meantime. Lighter weight means that it may also be practical enough to tote them with you in case you are concerned about vandalism or theft. Taking Pb 8D's in your SUV might flatten the leaf springs. :)

    These are the things that change your operations a little bit, and may or may not be worth the initial upfront cost now. They aren't for everyone. I seriously doubt you'll ever see them at the local autoparts store, except for the small powersports SLI types.

    I'm happy with lead - once I ran across forums like this and guys like you that pointed me in the right direction on how best to take care of them and design a system around them! However, I am happier with lifepo4 when I took in the operational characteristics.
  • zonebluezoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    Im enjoying your thread too. Agree 100% that current price isnt the only factor. Judging by the way production is ramping up on these, we will see some good price drops in the next 2 years. Getting hold of the things in this part of the world still a major hassle.

    Im still gathering data to make a proper cost benefit analysis. A guy on the midnite forum has just imported a 200Ah 48V bank. The cost shipped to the door was AUD5800. Kinda eye watering, no argument there. That amounts to (simplisticly):
    				LifePO4		AGM
    				(rw)		(zb)
    -----------------------------------------------------
    Cost (NZD)			6264		2500
    Nominal bank (V)		48		24
    Rated capacity (Ah)		200		400
    Total storage (Wh)		9600		9600
    DOD				80%		50%
    Usable storage (Wh)		7680		4800
    Rated cycle life		2500		1500
    Use case cycles/d		0.5		0.5
    Life expectency (y)		13.7		8.2
    Lifetime energy deliv (kWh)	19200 		7200 
    Lifetime cost/kWh ($)		0.33		0.35
    

    Nominally his and my banks are the same size, but his has more usable capacity and a higher cycle life. Whether the lithiums will reach their cycle life ( or the AGMs) is unclear. Based on this simple analysis theres not much in it for now. But if you were to factor the charge efficiency, things might start to get interesting, maybe.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    You may want to look into something closer, like EV Power Australia Pty Ltd and see how that stacks up.

    We can bench-race paper specs all day long, but in the end it comes down to just using what one feels comfortable with. For instance, I'd much rather have a fresh set of Pb Rolls / Trojans / Concorde batteries and replace them a few times, than receive some unsafe lifepo4 junk from an e-bike retailer, and use the "drop in" replacement chargers which run at too high and low voltages! :)

    Fortunately, the places I can get GBS, CALB, Winstons etc cells are very legit, and usually stocked nearby. Of course I shun the use of balancing boards in our application, provided one does a sanity-check on the first charge, but to each his own.
  • zonebluezoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts
    PNjunction wrote: »
    We can bench-race paper specs all day long, but in the end it comes down to just using what one feels comfortable with.

    Comfortable, like am i "comfortable" investing 6K in an still evolving, un-time-tested tech? Im fine with investment, but it needs to be based on sound return principles. As it stands the payback is only there if a) the cycle life stacks up, and b) the calendar life exceeds the cycle life.

    There are a couple of distrubuters here, but their prices are way higher than importing them yourself. That figure 6+K is the price for imported direct form the manufacturer, Highpower i think it was. Their prices seemed about the same as CALB and Sinopoloy. Import taxes, and freight.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    Hence the reason for my review of the smaller sized batteries. There is no way I'd recommend anyone put 6K into a bank without getting some hands-on first! Unless you already own a yacht to house them properly! :)

    Seriously, if you were contemplating this somewhere down the line, I would recommend that anyone start out small with some hands on before making a big jump like that. Even though the marine guys have been successfully using them for both house banks and even propulsion for about 4-5 years, I had to see it with my own two eyes - on the Flukes. Glad I did, because if I just jumped into a 6K bank I probably would have burned them up taking them to unnecessary extremes.

    And if you start with something small, by the time you are convinced this is a way to go, prices should have fallen even further. In my case, after a week I jumped at the 40ah, and really wished I went straight to 60 or 100ah once I demonstrated that I could take care of them.

    Consider me your cycle / calendar life tester. The only problem is I'm not sure the forum could withstand 8 years of my hot-air about them. :)
  • zonebluezoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    No worries PN. My first post here, BB bill reassured me that this forum thrives on hot air.

    For the record 95% sure our next bank will be LiFePO4. or sodium ion if that ever eventuates. As you say its not real hard to see a trend forming away from lead, despite the present numbers.

    Ive been working my way through Scheer's books, and that guy had a way of seeing things long before the rest of us could. I was still saying as recently as 12 months ago that solar still does not stack up. But without understanding the nature of the trend line, you cant see what is in effect a radical radical, establishment altering, transformation occuring, a complete new energy paradigm. He saw this solar revolution coming back in the 80s. He would not have had to live much longer to see that revolution take place.

    Scheer also said that it's a mistake to focus soley on costs. You hear that here a bit as well, and for a long time that has been a handbrake to solar investment, investment that is needed to bring costs down.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    There is comfort in lead - provided that prices don't rise. It is well understood, has a century or more of use behind it, and in the hands of the knowledgeable, they can wring the most out of it. It won't be going away tomorrow either. There is nothing really new to learn, and that itself is comfort in today's ever-changing world.

    I had known about lifepo4 for years, but never knew when I felt it was time for me to jump in. Once prices came down from the stratosphere, and most importantly, became available without having to deal with overseas factories directly, I went for it. Even so, I would not feel comfortable with only a single-vendor, and was glad to see competition among the brands with their own special sauce. That is, GBS is actually LiFeMnPo4 with manganese and apparently a different additive than PVDL, Winston uses Ytrrium (LiFeYPo4), and CALB sticks to just the pure stuff. I liked seeing competition. It doesn't exist solely in a lab and I can get my hands on it easily as a common man.

    I could always wait for the next chemisty around the corner, but there is no guarantee that it is not just vaporware, or bait for investors interested solely in patent-trolling.

    What almost put me off however was the myth that the lowest of the energy-density chemistries in the li-on family should be treated like the highest and most unstable types. That kind of FUD sells a lot of product, or just leads one back to the comforting arms of lead.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    I should have left well enough alone!

    While I was pretty much satisfied with the balance out of the box, I gave in to the tempation to make things better on my own by simulating an active balancing system. About every other cycle I was "touching up" the voltages in an effort to get them exactly the same voltage with my rv bulb discharger.

    Big mistake. Eventually, it got out of hand, so back to the basics.

    Using the single-cell 6A / 3.7v charger, I merely charged each cell individually, and watched for the current to drop with my clamp-on ammeter to about C/20, which in the case of the 20ah battery was about 1A. Each cell when charged individually settled in to about just 3.675v on a Fluke meter when that happened, but I was letting current be my guide, not so much the voltage. This is NOT the voltage I'm driving them to under normal conditions. I did not need to let the charger actually finish and attempt to bring the current down to zero. C/20 was fine enough when I pulled the charger.

    If I was using a charger at less than C/20 capability, then I would have stopped at 3.45v or so. But I find that using a charger larger than C/20 provides a nice indication when absorb starts to occur to make it easier to determine when to stop.

    The end result is that with either the Samlex charger set for 14v max, or my Xantrex set CC to 14v, (3.5v per cell under charge) when fully charged and allowed to rest for at least 2 hours, I come away with no more than 0.006mv delta worst case. :

    3.364v
    3.362
    3.364
    3.358

    Repetetive cycling at a max of 14v total with the Samlex or Xantrex, and measuring after a two hour rest minimum, I always obtain the 0.006mv delta. Sometimes it is 0.008mv if I am impatient. They are staying that way, and I even achieve about 90% DOD before small variations among the cells start to diverge somewhat.

    With the GBS cells, 3.35v to about 3.38v after rest indicates a full charge. Not that it means they are exact in capacity or internal resistance, but operationally with my low-voltage, low-current application, I can take this to the bank.

    My meddling proved to me that trying to actively balance cells while under charge, or immediately thereafter, is a guaranteed way to put your battery on artifical life support forever. No more of that thank you, I'll stick to just charging to C/20 current individually once, and thereafter run at a lower voltage and be done with it, aside from performing sanity checks once in awhile.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    More simplicity testing for those that obsess over balancing ...

    Because I was bored, I wanted to see what would happen if I seriously unbalanced the 4S string of my GBS 40ah battery. I discharged each cell to random levels with the RV lightbulb. Could I recover?

    Two key issues here is not to overcharge any cells past 3.60v, and be able to obtain at least 80% of the rated capacity under discharge, without driving one or more cells too far down into the knee.

    With a limit of 14v max on the charger, one cell soon started to exceed 3.6v *well* before the others. STOP. Sure enough, badly unbalanced. I'm keeping in mind that this is an SOC voltage, and not a true test of capacity.

    Using the single-cell charger, I charged each cell until about C/10 current was reached on my clamp-on ammeter. In a previous test, I stopped at C/20. I found that there was no need to go even that far. Subsequent charge / discharges netted about a 0.080 voltage difference from highest to lowest when an overall battery voltage of 14v was reached. Cell voltages hovered between 3.47 to 3.55v.

    Now no cell reached 3.6v. While one of them was lower at 3.47v, the crucial test was I able to obtain 80% DOD without driving too far into the knee?

    YES!

    This would be good enough for me. BUT, being obsessive about it did lead me to finely tune each cell with individual RV bulb discharges until I reached the point where under charge, the cells were about perfect at 3.511 to 3.514 volts before the 14v charger fell back to float. (unnecessary to float!)

    Did I get anything out of it? NO. I still stopped my discharge at 80% DOD, about 12.8v overall (3.2v per cell). Ok, one of them was at 3.17v. Big deal. Operationally, achieving a nearly equal SOC voltage under charge didn't change a thing. As long as the cells are *reasonably* similar in overall capacity, IR etc, you'll be fine. But they don't need to be absolutely perfect!

    One amazing thing I did discover is that if you try to balance individual cells while under charge by using a small load like the RV bulb, while you will be able to obtain a "balance" while charging, you'll be needing to do that each and every cycle! It gets even worse if you use a higher overall voltage like 14.4v. Utterly ridiculous.

    In the end, I proved to myself that under our energy storage application, normal two-terminal charging is fine even if things aren't exactly perfect. If your vendor states that they were already pre-charged, (typically at half-full SOC) on the first charge up to around 14v, just keep an eye on them to make sure that one cell doesn't go over 3.6v. If it does, either you'll want to temporarily break out the single cell charger and charge each cell individually once, or do a slight discharge on high cell(s) and try again. But once you are done, you are good for everyday normal charging at no more than 14v.

    This reads harder than it really is. I don't know why some want to make it complicated. Actually, I $$$ do. :)

    Don't treat them like "drop in replacements" with high voltages 14.2v+. 13.8-14v is fine. Don't let any cell go higher than 3.6v. If it does, tune it up a little bit, but no need to bananas. While you can go to 80% DOD, no solar user is going to purposely undersize his battery to go there. If you do, then at our relatively low-current rates, you should have plenty of time even with a mere pack-voltage level alarm to prevent any one cell from diving to the bottom. That is, if you started out with quality like GBS, CALB, etc, and not some used homebrew e-bike trash.

    I always have a hard time keeping in mind that we are NOT motive-power/ EV / RC / Wheelchair users that live or die on using the last ounce of capacity to make it home or on the ground. We have some breathing room, and this can be a hard thing to wrap your head around when formerly dealing with other chemistries that wanted to see exacting voltages and procedures for the longest life. Lifepo4 - don't overcharge - don't overdischarge - don't obsess over not obtaining a "full" charge - live life in a psoc environment and you'll go even further. Be happy. :)

    Note for wheelchair users - while these large GBS / CALB cells are great for high-voltage EV use, at 24v for a wheelchair, you'd be pulling HUGE amounts of current - and in that case then cells that have more instant power capability, like cylindrical Headway's should be considered. For our solar storage application, they would be a waste of money, and the large prismatics are better suited - and even then most won't even tap their true capability when doing solar provided they don't make a dinky little pack driven to 80% DOD on a daily basis. :)
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    Disclaimer, I don't know anything about LiFePo4, but am preparing for when I need to replace my lead acid's in (hopefully) more than a decade's time :)

    If the problem is overcharging individual cells with too high a voltage, how about using a step based charger that measures charging current and changes its voltage accordingly? E.g. assume a bank of 4 cells, 3.2V each
    1. charge the whole bank at 13.2V
    2. measure the charging current, if very low or 0 then increase charging voltage by 0.1V
    3. Repeat until all cells reach the right voltage

    This would be possible right now using a midnite classic CC + small computer to do the monitoring and setting the target voltage.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts
    stephendv wrote: »
    Disclaimer, I don't know anything about LiFePo4, but am preparing for when I need to replace my lead acid's in (hopefully) more than a decade's time :)

    Great! Now you can pick up one of the smaller batteries like I did, and have a decade's worth of experience behind you before you pop for a large bank! :)
    3. Repeat until all cells reach the right voltage

    Not really necessary to make sure ALL cells reach the same voltage, just don't go over 3.6v. Operationally there is no practical difference with a slight imbalance in soc ending voltage. And due to individual differences in internal resistance and manufactured cell capacity, we are really fooling ourselves and just satisfying a need to try and make metering read the same.

    The EV guys that "bottom balance", which we don't need to do, do just that - they terminate charge when ONE of the cells reaches say 3.5v and call it a day. They don't fret over a ragged top-balance. We really don't need to either, assuming we are *reasonably* balanced at the outset.

    In other words, if I took my cells to Dalhousie U. and measured them after my "perfect" balance, I might very well indeed be truly more UNbalanced in overall storage, than when I had a difference of 80 millivolts between high and low on a previous attempt! Sounds strange I know, but without knowing IR and exacting capacity specs, I'm just dancing on the head of a needle only because I can, not because I have to. :)

    Cells are considered fully charged at 3.45v. But it takes a little more, like 3.5v per cell to get there. After several hours rest, due to differences in IR and manufactured capacity, the measured ocv can be anywhere from 3.35 to 3.4v. One can go nuts over end-amps and absorb, but once you start the absorb cycle, you can just stop. No need to finish it really, unless you are going to miss being 1% under-charged. :)

    The key to simplifying life is to drop the voltages below those of "drop in replacement" voltages. Instead of shooting for 14.4v, set a target voltage of 13.8 to 14.0. The cells will still be fully charged, it just takes a bit longer and gives you some leeway in balance. My CC's are set to 14v (NO temp-comp!!), and my Samlex AC charger is also set for 14v max. Works great.

    So yes, a very smart charger could be used initially, but after it's single use, it will gather dust as you go back to normal two-terminal charging. :)
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: GBS LiFePo4 20 and 40ah batts
    PNjunction wrote: »
    With a limit of 14v max on the charger, one cell soon started to exceed 3.6v *well* before the others. STOP. Sure enough, badly unbalanced.

    If instead of starting to charge at 14V, you started to charge at 13.2V then there'd be less of chance that any one poorly charged cell would hit 3.6V. By gradually stepping up the voltage, bit by bit, I would _guess_ that there's less of a chance of overcharging any one cell.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: GBS LiFePo4 20 and 40ah batts

    Sure - that would be a good idea for doing the very first "sanity" charge check. Especially if one is putting a random pack of cells together. Both of the batteries I received (already cell-joined and strapped) were very close in balance initially anyway. (as determined at the end of charge, NOT upon receipt, where voltages, even if perfectly matched, mean little.)

    Some have been known to use hobby chargers like a Revolectrix PowerLab charger to do this automatically which charges each cell. That would be cool I guess, but for me it would be a one-time use. :)

    If you could program a solar charge controller to do something like this, even just once, that would be very cool, but I suppose you would need cell-level monitoring, something I don't feel the need for. Still, for a one-time use, nice!

    Just resist the tempation to over-complicate both the charging and use of lifepo4 in house-bank duty. It really isn't that hard, but there are plenty out there that want to empty your wallet or time convincing you it isn't - usually based solely on prior experience in non-related applications, like EV or RC modeling.
Sign In or Register to comment.