LFP or LifePo4: questions about using

I am contemplating buying a LFP or LIFEPO4 battery system for my off grid farm as the advantages of the LFP battery fit my particular requirements very well.

I am interested in hearing from those of you who have LFP battery systems. If you could help me out with specific assurances I would be most grateful.

One: Did you find that the batteries charge much faster than with FLA?
I hear they are 95% efficient. I have a 3 month period at the farm where the days are getting shorter and the cloud cover is heavy and persistent. I often only get a few hours of bright light a day. I have even recorded one day with 0 watts from a 1.5 kw solar system. A more efficient charge will benefit me. Your experiences?

(I did read one British fellow who has had his system for over a year say his "equalize" stage is 10 minutes. Yikes!)

Two: How do you measure the remaining power in your battery bank if there is no change in the voltage?
Are you using some kind of amperage monitor (trimetric or similar?)

Three: Has anyone used this system in a very cold climate? Did your battery maintain full power at this kind of temperature?
I have recorded battery temperatures as low as -17C (essentially 0F). I was pretty much forced to use my system for lights only. Now I have an electric fridge, water pumps, etc so I am forced to heat my batteries. I would like to do away with this requirement.

Thank you for your time and assistance in this query. Any other thoughts or glowing admiration for your battery are welcome. Love and happiness. Creeky.
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Comments

  • Alaska ManAlaska Man Solar Expert Posts: 252 ✭✭
    Re: LFP or LifePo4: questions about using

    I think the concensus is, many believe they will work if they perform as advertised, but most are reluctant to be the first one on that band wagon.

    Please let us know what you find out if you decide to take the leap. There have been some who have tried very small LifePo4 batteries and have posted positive results.
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Re: LFP or LifePo4: questions about using

    Maybe also add your system spec to your sig, that will help others in their responses.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • ReedReed Solar Expert Posts: 55 ✭✭
    Re: LFP or LifePo4: questions about using

    Have noted earlier from joining the Aussie group The Grey Nomads, that the New Zealanders and Aussies are far more receptive to new ideas. Have responded to Creeky by private message.
    Reed and Elaine
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: LFP or LifePo4: questions about using
    creeky wrote: »
    I am interested in hearing from those of you who have LFP battery systems. If you could help me out with specific assurances I would be most grateful.

    The easiest way to do that is to start small with a little system of your own. Such as that I describe here:
    http://forum.solar-electric.com/showthread.php?23898-GBS-LiFePo4-20-and-40ah-batts

    You'll find the information needed to get started, and be able to answer your own questions with some direct hands on.

    While I described my own experience with GBS cells, that is a *generic* recommendation, and the review tries to avoid much of the hype and salesmanship, and stick to the technical facts. For many, these facts are NOT worth paying for when lead works just fine when properly engineered.

    Climb on board the hands-on train, and we can give valuable technical feedback to the group as time progresses, devoid of salesmanship and hype. I'll be happy to answer any questions to get you started - see you there!
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: LFP or LifePo4: questions about using

    Cheeky,
    One of the first things you will probably hear as you follow the subject is that unlike lead-acid, the Li batteries, including LiFePO4, do not like (and certainly do not require) being charged to 100%. Storage at 100% will decrease life much more than storage at ~80%. And the charging efficiency is lower in the top part of the charge. As a result those of our members who have studied and started experiments advocate getting a large enough bank that you routinely cycle between say 40% SOC and 80% SOC, unlike FLA where your target cycle is between 80% and 100%.
    If you need multiple days of autonomy and do not want to use the generator much, raise the design lower limit of SOC, and only charge above 80% if you see a long dark spell approaching.
    SMA SB 3000, old BP panels.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: LFP or LifePo4: questions about using

    Ok, I guess I could have been a little more direct ...
    One: Did you find that the batteries charge much faster than with FLA?
    Yes. Actually faster than my pure-lead agm's, which I love. Due to the extremely low internal resistance, they charge very quickly with very little heat.

    The type of cells / batteries we use comes primarily from those destined for the EV community, (large prismatics) and have a typical max charge / discharge rate of 1C, although most users recommend no higher than 0.5C. They will take bursts up to 3C or more for limited amounts of time. Small cylindrical cells, which we don't use, have even higher charge discharge rates. The Peukert effect almost goes unnoticed in our application.

    This is important. For any reasonably sized bank that we intend to get us through the night, you will NEVER use that high of a charge / discharge rate - especially so with cylindricals. So while this gives us the freedom to use huge amounts of power very quickly, that advantage goes away when you design a bank for energy storage, and not propulsion like an EV.

    In other words, if you had an 800ah bank, you'd be hard pressed to find a 400ah (conservative 0.5C charge rate) charge source. And, unless you only designed your bank to last a little over an hour, you wouldn't be pulling 800ah from it either. The *claim* is that in our application where we use them with such relatively low current needs, they will last longer. Claims and speculations since nobody has done 10 year or more studies on them. But I'm on board to let you know in a decade!
    I hear they are 95% efficient. I have a 3 month period at the farm where the days are getting shorter and the cloud cover is heavy and persistent. I often only get a few hours of bright light a day. I have even recorded one day with 0 watts from a 1.5 kw solar system. A more efficient charge will benefit me. Your experiences?

    If you have the means, then you could easily set up a solar array to charge your totally depleted (80% DOD actually) bank in about 2 hours or less, due to the low internal resistance. But that takes standard solar planning of knowing your exact loads, insolation hours, desired autonomy and the like. No magic here.
    (I did read one British fellow who has had his system for over a year say his "equalize" stage is 10 minutes. Yikes!)
    He's probably talking about a "balance" stage where one actually drives the system higher than normal just to get the bleed-off resistors to walk the cells down to each other. What you'll find out with the hands on is that a conservative approach of not charging up to 100% is not only unnecessary, but it drastically simplifies things so that balancers are not actually needed. Yes, you need to start out relatively close in balance, but once done, it stays that way especially since we are what they call a "Sub-C application". Low-voltage disconnects, yes, but constant balancing is not really needed. But don't trust me or the bms industry trying to sell you something. With conservative settings, you can easily reach your goals and leave the battery looking like a battery, and not something on the mars-rovers.
    Two: How do you measure the remaining power in your battery bank if there is no change in the voltage?
    Coulombic counting is the best so far. SOC voltages are not exact, BUT there IS enough of a slope that you can ballpark it with voltage. Once again, hands-on can prove that.

    As for the cold near freezing, I would suggest using something like the CALB CA100FI series of cells that have better performance near 32F. You can find many interesting charts, manuals and so forth about - a quick search will turn up some nice charts. I'll let others chime in there since I'm currently beating mine with 105F and only wish I could have a cold day once in awhile. :)
  • sub3marathonmansub3marathonman Solar Expert Posts: 300 ✭✭✭
    Re: LFP or LifePo4: questions about using

    Since this is "questions about using," the biggest question seems to be about the Battery Monitoring System, and I think this is what creates a lot of the angst about these batteries.

    Some say it's crazy to not use a BMS, others say you're asking for another point of failure with a BMS and that many systems have been destroyed by them.

    There is a simple, cheap monitoring system, the Cell-Log 8M, that just keeps track of cell voltages. Is it possible that something so simple could be used when many of the BMS cost hundreds, if not over 1000 dollars?

    PNjunction says "Coulombic counting is the best so far." So what is considered the good one to use for that? And that is in addition to the BMS.

    People know that PbA batteries can withstand abuse, whereas Lithium seems, perhaps incorrectly by those who don't know (such as me), more like a delicate china vase that could break just by looking at it wrong.
  • BB.BB. Super Moderators, Administrators Posts: 29,980 admin
    Re: LFP or LifePo4: questions about using

    As long as your are talking about LiFePO4 batteries--It does not sound like they are really any more "fragile" than Lead Acid AGM batteries--Both can easily be damaged by over charging / too high of charging voltage. But because (as far as I can tell) LiFePO4 batteries are not temperature sensitive--They are actually easier than AGM to properly charge.

    Both (all lead acid and LiFeP04) batteries are also easy to damage if taken below 20% state of charge too. Again, the LiFePO4 batteries without temperature compensation are actually easier to monitor with a simple volt meter.

    Lead Acid have better operating characteristics for sub freezing applications--But can be damaged too if you do not keep an eye on them.

    Have to be very careful here--The various Lithium chemistry battery types have very different behaviors. Don't want to mix and match "issues" across the entire Li Ion family.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ReedReed Solar Expert Posts: 55 ✭✭
    Re: LFP or LifePo4: questions about using

    As noted earlier, figured that PNJunction could a lot better theoretical understanding of what is required and expected. He likes to keep things simple and does not care for the expense of a battery management system but just sets controller to keep battery bank at 80% (54.6 V for our 48 V nominal system) as he explains in his post. Our BMS does run the voltage to 57.6 V for absorb until all cells are at 80%) and then sets at float of 54.6 V. Our system came with the BMS since it was designed for EV work.

    I do not think that LFP will break just by looking at them as some nay-sayers state. The military has been using them quite successfully on fighters and armored vehicles for years.

    Reed and Elaine
  • PhotowhitPhotowhit Solar Expert Posts: 5,077 ✭✭✭✭
    Re: LFP or LifePo4: questions about using

    Here's an article about military development contract.

    What I find interesting is they are developing a 12 volt battery! I thought military vehicles were 24 volt? I think the Military Humvee's are...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: LFP or LifePo4: questions about using
    Photowhit wrote: »
    Here's an article about military development contract.

    What I find interesting is they are developing a 12 volt battery! I thought military vehicles were 24 volt? I think the Military Humvee's are...

    Some military/industrial vehicles are 'split 24 Volt' using the connection between two 12 Volt batteries as chassis ground and then having a -12 Volt and +12 Volt wiring. This allows standard 12 Volt items to be used where 24 Volts isn't needed and reduces sustained arcing problems (either wire shorts to chassis at <15 VDC). LiFePo would be good here because of the inevitable imbalance between batteries cause by only one side powering the 12 Volt items. BMS would make that even better.

    Oh and lets try not to confuse Battery Management System with Battery Monitoring System. Same initials, different function.
  • ReedReed Solar Expert Posts: 55 ✭✭
    Re: LFP or LifePo4: questions about using

    LiFePO4 have working voltage = 3.0 ~ 3.3 V. Four cells in series having working voltage = 12 to 13.4 V. This would be considered a 12 V nominal battery. A 24 V nominal battery would have eight cells in series. Our system has four batteries (each of 4 cells in series) in series for a 48 V nominal battery bank.

    Lead acid batteries are fabricated in the same manner. A 12 V battery has twice the number of cells as a 6 V battery. Hey, I was just a senior applied physicist for Army Research Laboratory. I can understand theory, just don't expect me to fix anything requiring more than a hammer, prybar, duct tape and WD-40. The technicians I worked with were convinced I adjusted the timing on my BMW motorcycle with a hammer in blowing sand. Heck, all you need is an appropriate sized hammer: smack it to make it loose, tap it to peen it together (don't need duct tape and WD-40 - my toolbox just got lighter) .
    Reed and Elaine
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: LFP or LifePo4: questions about using

    No duct tape?
    You won't be allowed to work in Canada! :D
  • creekycreeky Banned Posts: 31
    Re: LFP or LifePo4: questions about using

    Thank you Reed and PNJunction for your replies.

    I have contacted Balqon about the cold weather issue. In the brochure they mention "Operating Temperature -45 deg C to 65 Deg C" while Crown specifies that you not use their batteries below -18C.
    And, of course, FLA capacity diminishes as they get colder.

    Note: The Balqon has built in monitoring, low discharge warning, and "proprietary cell balancing" whatever that is.

    ***a bit off topic, but related...

    inetdog. Humour... always appreciated. At 40 to 80% dod I would have roughly 4 kw of power. My FLA pack gives me 2.5 (we can quibble here) I try to keep it around 2 max for longevity (20% dod). At the 40-80 discharge level I should get something around 13 years of lifespan off LFP. While my FLA at 20% dod is more like 3000 cycles or 8 years. Which is the current (heh heh, I love this pun) FLA standard I believe.

    Looking at cost: Interestingly, the Crown FLA is 385 bucks now. x 6 = 2310 before shipping (I paid 1,800 back in the day, before fuse and wiring of course). While the balqon is 3350 shipping inc. Initial cost is not so far from equivalent. If I take a bit shy of double the life span - 5000 cycles (tho it's 7000 cycles if I keep to my 2kw power use, so double and a half) that's, call it 4,200 for FLA (or comparing equal 2kw power use 5775) vs 3350 for LFP.

    I will almost undoubtedly increase my power use with the new pack. I don't enjoy doing dishes and I would like to use my dishwasher more often. I'm waiting for tomorrow, 8 hrs sunshine in the forecast, to do dishes. Meanwhile the fruit flies gather.

    I suspect any battery used in vehicles, for a decade now, is hardly a china vase.

    I look forward to more posts that relate to the actual use of LFP systems. Thanks again. Creeky.
  • ReedReed Solar Expert Posts: 55 ✭✭
    Re: LFP or LifePo4: questions about using

    Quando Omni Flunkus Moritati
  • Mountain DonMountain Don Solar Expert Posts: 494 ✭✭✭
    Re: LFP or LifePo4: questions about using
    Photowhit wrote: »
    Here's an article about military development contract.

    What I find interesting is they are developing a 12 volt battery! I thought military vehicles were 24 volt? I think the Military Humvee's are...

    My Toyota Land Cruiser diesel has 2 - 12 volt batteries auto batteries. The starter runs on 24 volts and the balance of the vehicle's electrics are normal 12 volt. That helps with starting at -30 F
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: LFP or LifePo4: questions about using
    My Toyota Land Cruiser diesel has 2 - 12 volt batteries auto batteries. The starter runs on 24 volts and the balance of the vehicle's electrics are normal 12 volt. That helps with starting at -30 F
    Once had a 1965 Datsun pickup truck with a 6V system. In the winter the battery could not provide a high enough voltage for the ignition to work while at the same time cranking a cold engine.
    The solution was to turn the engine over a few times with the starter, then leave the ignition on and fit the hand crank into the front of the engine. (AFAIK that model was only shipped to the US for one year.) :-)

    Straight 4-cylinder engine with overhead valves driven by pushrods from the crankshaft. Four speed transmission and rear progressive leaf springs with rubber snubber blocks for when heavily loaded.
    SMA SB 3000, old BP panels.
  • creekycreeky Banned Posts: 31
    Re: LFP or LifePo4: questions about using

    Thank you Cariboucoot for deleting the side tracks. It will make for better reading for all.
  • Mountain DonMountain Don Solar Expert Posts: 494 ✭✭✭
    Re: LFP or LifePo4: questions about using

    I have read more about LifePo4 batteries in the past week than in my entire previous years alive, and I have not been a spring chicken in many a decade. :roll: I can appreciate some of the touted advantages. However, I still really want to see real life long term results from real off grid users with large capacity batteries used in a typical RE situation. I still have sticker shock every time a product price page comes up. The potential life of a LifePo4 battery is somewhat dampened by knowing how much money would go down the tubes if "something" bad occurred. Time will tell how this works out. In the meantime I'll 'make do' with my FLA's.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: LFP or LifePo4: questions about using
    creeky wrote: »
    Gee, bullies in school used to just punch the new kids. But I guess here they just act like a*chew.

    Wondered why there were just a few "frequent" posters and not many others. Creeky out.

    It's your thread: if you like I can delete all the side-tracked posts.

    You won't receive much response because the simple fact is there aren't many using LiFePo4 batteries in RE applications.
    Yet.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: LFP or LifePo4: questions about using
    Since this is "questions about using," the biggest question seems to be about the Battery Monitoring System, and I think this is what creates a lot of the angst about these batteries.

    There is a lot of confusion about this, stemming mainly from not adequately describing what a "BMS" is.

    Most of us using lead are using a BMS without calling it that. It consists primarily of a Low-Voltage-Disconnect and a High-Voltage-Disconnect. The LVD can be anything, like in the marine world using something like a Blue-Sea-Systems m-lvd. The HVD is usually just the upper voltage limit you set on your solar charge controller, or ac charger. However some take it even further with an additional hvd beyond the charger. Balancing consists of either running an EQ on flooded, or at least reaching the gassing voltage on agm.

    You can have your own "bms" like I do with separate hardware. My charger is the HVD. My LVD is either my brain knowing my load limitations (risky), or using something like a Powerwerx ITS-12, with it built-in timed LVD at 12.8v, albeit designed for lead, works perfectly in my lifepo4 application. There are many ways to incorporate an lvd and hvd of your own choosing.

    Balancing is usually the big seller, and thread destroyer. :)

    I have proven to myself that with conservative settings (like 14v max on your CC or ac charger), and an lvd of 12.8v - maybe 12.7v, if you have a reasonably balanced pack to start with, you won't be going nuts needing additional hardware. Most of the balancing scare tactics come from outside our application, like those of EV'ers / Ebiker's, DIY'ers using substandard cells and infrastructure, or RC modelers using an entirely different chemistry with different characteristics. Or you may want to employ a "single cell" charger, usually limited to around 3.7v - and they come in a variety of amperages to get the job done quicker.

    That is not to say that you can just willy-nilly put 4 lifepo4 cells together at random and cross your fingers. You wouldn't do this with a lead-acid based bank using 2v cells either! There are techniques discussed at length on how to do this elsewhere, or one consideration might be letting a commercial bms with balancing do the balancing, and then once that has been established, run at a conservative voltage so as not to constantly trigger the cell balancing circuits. In a "sub-c" application like ours, we are not pushing these cells so hard. Once in balance, they tend to stay that way, or at least in the state you found them.

    In the case of a simple 4S / 12v battery up to about 100ah, one could just as easily use a Tecmate-Optimate Lithium (lifepo4) charger, that does NOT use individual cell balancing, but only two-terminals do it's thing and call it a day. I did, and it works a treat.

    Some view a bms as "insurance", and that's fine with me. However, to me, if a battery can't stand on it's own, using standard charging methods without using external life-support balancing circuitry, then that is not acceptable as a battery in my terms. Hence, my battery is emulating how I would use it just like I would a lead-based battery - a little conservative care goes a long way.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: LFP or LifePo4: questions about using
    .. There is a simple, cheap monitoring system, the Cell-Log 8M, that just keeps track of cell voltages. Is it possible that something so simple could be used when many of the BMS cost hundreds, if not over 1000 dollars?

    Yeah, if you are willing to trust a $20 RC-modeling hobby voltmeter on your $2K or more bank! Specs are one thing - have you verified each and every channel with something you trust like a FLUKE voltmeter, and not some cheaper brand? Trust is crucial. So too is verifying the $8 balancing boards for correct operations. Do they each trigger at 5.5v, or do some trigger at 5.1, 5.7, 5.5, 5.4? Will they actually last in a real world environment? That is a lot of trust placed upon an $8 dollar board on very expensive batteries.

    For me, no thanks. Conservatism keeps my batteries free of these POF's and the quality of the cells is trusted so I don't need individual cell monitoring. If one cell takes a dive, I want to know right away, complain to the manufacturer loudly, and possibly shop elsewhere if my needs aren't met. Just like I'd do with lead.
    PNjunction says "Coulombic counting is the best so far." So what is considered the good one to use for that? And that is in addition to the BMS.

    If you are getting into this game, you'll be wanting to look beyond the RC modeling products. Would you put a Junsi Cell-Log 8 on your bank of 2V Rolls-Surrette's? No. :)

    Our own host has a nice Blue-Seas BS-8248 volt and ammeter with alarms triggers. I might look into that when I go big league. For now, my Fluke voltmeters and ammeters do nicely for sanity checking. Leave the $20 hobby stuff.

    Victron Energy's "bmv" line is something worth looking into for coulombic counting. You can build your own "BMS" with items from various manufacturers, just like any serious installation does with lead.
    People know that PbA batteries can withstand abuse, whereas Lithium seems, perhaps incorrectly by those who don't know (such as me), more like a delicate china vase that could break just by looking at it wrong.

    They aren't that dainty. There are those that just don't know, or base their opinion on other chemistries like LiCo02, or other non-related applications. Just avoid salesman claiming you don't have to anything - they are still batteries that you don't want to abuse.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: LFP or LifePo4: questions about using
    creeky wrote: »
    I have contacted Balqon about the cold weather issue. In the brochure they mention "Operating Temperature -45 deg C to 65 Deg C" while Crown specifies that you not use their batteries below -18C.

    Ok, that's all well and good, but like any company, just having brochures or a web site does not automatically mean they will have what you want in stock, or have to be put through some extroardinarily expensive overseas-shipping situation like those of yesteryear. These days, you should be able to get what you want locally - at least in your state or nation, without lengthy delays or promises. I haven't had any dealing with Balqon, so I can't comment. But this goes more towards sales, and not technical issues, so I'll drop that part.
    Note: The Balqon has built in monitoring, low discharge warning, and "proprietary cell balancing" whatever that is.

    All well and good again. However, one of the reasons I run bare naked cells with conservative values, is that I don't ever want to get locked into a proprietary single-vendor system. I prefer to choose the cells I want, and the external hardware I want to incorporate LVD, HVD and the like on my own and mix and match to my liking just like I can do with lead. But that's me.
    Looking at cost: Interestingly, the Crown
    We've been over cost before and that only gets us nowhere and destroys threads - especially for those pioneers who are willing to use them for reasons beyond initial cost.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: LFP or LifePo4: questions about using
    Time will tell how this works out. In the meantime I'll 'make do' with my FLA's.

    That is a *very wise* thing to do, unless you feel compelled to go lifepo4 like I did.

    One of my mentors in another application (mainly large amperage SLI duty) who uses lifepo4 extensively, is one of the first to say that one should stick to lead (in this case agm) unless they are prepared to deal with lifepo4 *properly*. That is stated in msg #2 of a thread now over 1500 msgs long:

    http://www.advrider.com/forums/showthread.php?t=757934

    Anyone trying to brow-beat or push lifepo4 onto someone else not prepared to deal with it (although it is easy, but needs proper attention), either does not know what they are talking about, a saleseman, or someone else with an agenda.
  • Mountain DonMountain Don Solar Expert Posts: 494 ✭✭✭
    Re: LFP or LifePo4: questions about using

    Thanks for the advrider link.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • ReedReed Solar Expert Posts: 55 ✭✭
    Re: LFP or LifePo4: questions about using

    The question from Northern NM (our son lives at Las Dispensas, NM at edge of Pecos Wilderness) was "...I still really want to see real life long term results from real off grid users with large capacity batteries used in a typical RE situation..."

    We have been using the LFP for 15 months with 4500 miles of travel with a 34' 5th wheel through mountains of western US. We have had zero problems or even hiccups. We use m/w at all times and run the Doemetic refrigerator on AC during daylight and 24 hours a day if there will be full sun the next day. We have run a/c for 3.5 hours and could do more (we were down -4500 W-hours by that time and were cool). However, there are still few of us using relatively large LFP banks at this time.

    I read all that PNJunction has to say about varied things. He knows what he is talking about. He does not have a lot of requirement for a Battery Management System since he likes hand on work. We are much happier with something we can just monitor and that pretty much keeps things in line automatically. There are a number of fabricators of lithium cell systems in the US that folks seem to be happy with. Son has friends who are tinkering with and building EV vehicles (his brother-in-law is building a Toyota 4 x 4 EV) and is familiar with Manzanita Micro so he went with them for fabrication. The Battery Management System is designed for EV use (very high power drainage - we trialed system running both a/c and m/w for half an hour at about 3000+ W).

    The Manzanita write-up on their BMS is

    "...Anytime lithium cells are connected in series to make higher voltage battery packs, as is the case in electric vehicle applications, the usable capacity of the entire pack will only be as much as the capacity of the lowest cell. Even if a battery pack is well-matched when new, imbalances between the cells will occur over time. The primary function of a Battery Management System (BMS) is to facilitate equalization at the module or individual cell level so that the entire battery pack has as much useable capacity as possible.

    The Mk3 digital BMS line of products provides rapid monitoring of individual cell voltages and temperatures. The Mk3x4smt will manage 4 lithium cells, the Mk3x8 will manage as few as 5 or as many as 8 lithium cells and the Mk3x12 will handle between 7 and 12 lithium cells.

    All of the BMS units use an intuitive command structure and are very simple to set up. Real-time status LEDs on the boards themselves indicate high and low conditions as well as which cells are full (when dissipating energy during equalization). The red undervoltage latch LED is useful for spotting the weakest modules after adischarge situation (such as a long drive for an EV).

    The Rudman Bus Display (RBD) allows for an independent in-dash touch screen solution.

    Specific historical data of maximum voltage high and lowpoints are stored in the BMS unit's internal memory and can be easily viewed on the RBD or using thegraphical Reg Scanner program on a PC or even using simple text commands in any terminal program..."

    Each of our four batteries has a Mk3x4smt BMS (4 cells). We also have the Rudman Bus Display. We have not had to do any "solutions".


    Reed and Elaine
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: LFP or LifePo4: questions about using

    Reed - you've got a very nice system, and I'm glad that the Manzanita is working out for you. While I'm not disagreeing with your proven results so far, I do take issue with some of their statements. Not trying to start an argument mind you, but the following may be of interest.
    Reed wrote: »
    The Manzanita write-up on their BMS is
    Primarily coming from the EV industry with a financial stake in the matter.
    "...Anytime lithium cells are connected in series to make higher voltage battery packs, as is the case in electric vehicle applications, the usable capacity of the entire pack will only be as much as the capacity of the lowest cell. Even if a battery pack is well-matched when new, imbalances between the cells will occur over time. at the module or individual cell level so that the entire battery pack has as much useable capacity as possible.

    True, but at what level of intensity does that happen to make it impractical? Here we go ....
    As in the case of electric vehicle applications
    Yes, those who need the very very last drop of capability will be pushing these cells right to the edge of the envelope on either charge or discharge. We don't do that.
    Imbalances between the cells will occur over time
    Yes, for EV'ers who frequently run these things at 1C or more in a propulsion type mode. Of course there is also the problem of a tangled mess of sloppy / high resistance wiring to contend with that will do that as well. We don't run at 1C and our cell count is kept to a minimum ideally. In our energy-storage application, 0.1 - 0.3C is more the norm. At this rate, whatever state of balance you are in, it tends to stay that way. The "Sub-C" phenomenon.
    The primary function of a Battery Management System (BMS) is to facilitate equalization
    This is misleading, but reassuring to the EV crowd. Equalization is not something we have to obsess over in our application. Relatively equal, yes, but not to the level that these things take them to. For us, just don't exceed 3.6v on any single cell for any significant amount of time.

    This was also pushed back in the early EV days when one used FLA or recently introduced AGM's like Odyssey (actually Genesis). In many cases, what was once a properly operated bank of batteries became UNbalanced when the balancing circuitry became a point-of-failure. In many ways, the recent bms industry reminds me that we have not learned our lessons from the past. Spent a lot of time in the EVDL list back then.
    The Mk3 digital BMS line of products provides rapid monitoring of individual cell voltages and temperatures.
    Monitoring is fine. With our application of a tiny bit of conservatism, this will mostly serve as eye candy. Temperature? If you push these things BEYOND 1C, then things will start to get hot. We don't do that. Ambient temp monitoring is good, but cell temp in our application, provided you haven't purchased junk, is not going to be a big issue until you ge above 1C for long periods of time. I'm not into individual cell level monitoring and am demanding that my manufacturer make good cells in the first place, and do pack-level monitoring instead. For EV'ers, this also usually becomes a distraction like texting while driving, constantly putting an eyeball on the monitor obsessing over it.
    All of the BMS units use an intuitive command structure and are very simple to set up. Real-time status LEDs on the boards themselves indicate high and low conditions as well as which cells are full (when dissipating energy during equalization). The red undervoltage latch LED is useful for spotting the weakest modules after adischarge situation (such as a long drive for an EV).

    So is a simple Fluke multimeter, which you can trust out of the box. You are placing a lot of trust into a lot of 3rd-party infrastructure, AND is not usually verified against another calibrated source by the user for proper operation. If it fails, will Manzanita willingly replace your battery bank? Also again, they mention EV, not RV. :)
    The Rudman Bus Display (RBD) allows for an independent in-dash touch screen solution.
    In-dash, once again implying EV operations and history.
    Specific historical data of maximum voltage high and lowpoints are stored in the BMS unit's internal memory and can be easily viewed on the RBD or using thegraphical Reg Scanner program on a PC or even using simple text commands in any terminal program..."
    Nice, but I have a life to live. I don't need this with lead, relying on the quality of the compenentry in the first place from the battery manufacturer.

    The overall gist here is that this was intended as an EV, not an RV solution which you could shoe-horn into operation.

    Please understand I'm not trying to disqualify your system choice or advocating running without an LVD. You are obviously doing a very good job with it. I'm just trying to point out that if one is not careful, bet it a large or small system, there are those that want to operate under a "drop-in" mentality. With conservative care, we can bypass much of that and use our own choice of hardware, and also not obsess over absolutely perfect cell-balance - which in many cases just trying to achieve that does more harm than good.

    I told you this was a thread killer... :)
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Re: LFP or LifePo4: questions about using

    Given the small LFP using population, i take reasonably seriously teh numerous reports from people whose (poor quality or poorly connected) balance baords have imbalanced their banks. Thats like a breaker that welds closed, defeating its ultimate purpose.

    There are a lot of cheap balance boards around, no doubt about that, and frankly i take PNs view that you are better off without them, on average. However high quality units may appeal to some users that want a more hands off approach.

    However with the overall higher cost there is a somewhat natural tendency to reduce costs, and hence the cheaper units. Catch 22.

    For me Photowhits article is a good example of people who have justifiably done serious homework on LFP, and if they claim 4000 cycles v 400 for lead in deep cycle "hot environment" applications, then that 10:1 total lifecycle lifetime ratio should really grab our attention.

    Which brings us... right back to calendar life. Im farily confident that our present AGMs will die of calendar not cycles.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • ReedReed Solar Expert Posts: 55 ✭✭
    Re: LFP or LifePo4: questions about using

    Attachment not found.I agree with what you say. Son just wanted to make sure that we have hassle-free use of solar power when we are boondocking in US, Canada, Mexico, and Belize. A lot of folks such as yourself are do-it-yourselfers with electronics, and we are not. Son has worked extensively with varied types of PbS over 30 years in alternative energy research (NMSU) and as a licensed alternative energy/electric contractor and this was his first work with LFP and he went as conservative as he could in the development of this system - and that meant going with a "drop-in" system. He is a licensed master electrician (degree in EME engineering) and there was a lot of design/fabrication and reconfiguring and reprograming of the "drop-in:. Others such as yourself enjoy doing it yourself (DIY). A home has a lot more space to put things - and the room to work on them.

    Our original system was composed of glass mat batteries and we were quite happy with them. Unfortunately, they and the rest of the system are in a wrecking yard near Hernandez, Mexico. The system was still working after the truck and 5th wheel were totaled. There is only so much that even Mexican artisans and technicians can do.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: LFP or LifePo4: questions about using
    zoneblue wrote: »
    For me Photowhits article is a good example of people who have justifiably done serious homework on LFP, and if they claim 4000 cycles v 400 for lead in deep cycle "hot environment" applications, then that 10:1 total lifecycle lifetime ratio should really grab our attention.

    If you only get 400 cycles from lead-acid you are doing something horribly wrong.
    The cheapest among them should manage 2000 cycles.
This discussion has been closed.