Why not LiFePO4?

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  • PhotowhitPhotowhit Solar Expert Posts: 5,653 ✭✭✭✭✭
    Re: Why not LiFePO4?
    PNjunction wrote: »
    I'm just sad that nearly ALL discussion of Lifepo4 devolves beyond the technical / operational uses, and ends up in the usual political / marketing / emotional arena, much of it coming from those with no first-hand knowledge other than rc modeling or dramatic newsbytes which are often found wrong when the details are examined.

    I have looked through the thread, read it several times...

    All I see is pure Economics... If it's my money for my use... I want to save money... Save me money and I will buy your product!!!

    I have 804 Ah capacity, it cost me $2525 delivered and I can, from reasonable examples expect it to last 15-20 years. (you can use 15yrs, that's what I did even though I had heard of 30+ and NAWS 20+yrs. I stuck to known users experiences)

    Can you save me money?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Why not LiFePO4?
    Photowhit wrote: »
    I have looked through the thread, read it several times...

    All I see is pure Economics... If it's my money for my use... I want to save money... Save me money and I will buy your product!!!

    I have 804 Ah capacity, it cost me $2525 delivered and I can, from reasonable examples expect it to last 15-20 years. (you can use 15yrs, that's what I did even though I had heard of 30+ and NAWS 20+yrs. I stuck to known users experiences)

    Can you save me money?
    Where some of the justification fails is that a FLA battery is considered done at 75 - 80 % of capacity for traction service. Most in RE will just keep on using them until they won't service their needs. Most forklift and premium batteries have a 5, 7 or 10 year warranty. The 1,500 cycles or 5 years @ 80% dod will still be @ 80% capacity on a forklift battery.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Why not LiFePO4?
    Photowhit wrote: »
    Can you save me money?

    Yes. Unless you are solely grid-tie, then don't go solar at all since it already costs about 10x above what you are charged by the local poco. The choice of battery chemistry is almost a non-issue at this point. :)

    I'm afraid however that the signal to noise ratio is already so high in this thread, that any objective discussion about lifepo4 is moot, and lurkers have long since vanished.

    It happens not only here, but in nearly all other forums too. Sad really.
  • solar_davesolar_dave Solar Expert Posts: 2,382 ✭✭✭✭
    Re: Why not LiFePO4?
    feedhorn wrote: »
    Batteries are Batteries Big or Small:

    Nissan Leaf car uses LiFePO4 batteries. They had some problems in hot country like Phoenix ,AZ but now they have fixed that.

    Does anyone know what they fixed?

    I see Volts all the time here, with the active cooling the batteries are fine. Leaf's are like hens teeth! Pretty much sales seem to have tanked.
  • PhotowhitPhotowhit Solar Expert Posts: 5,653 ✭✭✭✭✭
    Re: Why not LiFePO4?
    PNjunction wrote: »
    Yes.
    Sorry I don't believe you!
    PNjunction wrote: »
    ...don't go solar at all since it already costs about 10x above what you are charged by the local poco.
    Sorry, I will agree the power company will likely be cheaper, but not by much!

    I'm no novice, I've been off grid for 13-4 years, I'm around 26cents a KWh, BEFORE tax incentives...

    Don't believe me? I did run the numbers, Here!

    I'm looking forward to the day it would be cheaper... It has it's place and I suspect the price will come down and may be competitive. I have no idea how you could come close with out an outside energy source and I really can't figure it out even then. I would trust 'Coot since he would look at it with that eye.

    FWIW - If you had intended to save me money by not having me be off grid, I was cheaper than the grid for most of those 13-14 years, only with new larger place did I go past the grid costs. This has to do with the $25 fee going to $32 in January, monthly for the privilege of buying electric at 9 cents, since I was a very minimal user the grid was costing me over 50 cents a Kwh. So the investment was made in the battery and a 2Kw array.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • sub3marathonmansub3marathonman Solar Expert Posts: 300 ✭✭✭
    Re: Why not LiFePO4?
    Photowhit wrote: »
    I have looked through the thread, read it several times...

    All I see is pure Economics... If it's my money for my use... I want to save money... Save me money and I will buy your product!!!

    I have 804 Ah capacity, it cost me $2525 delivered and I can, from reasonable examples expect it to last 15-20 years. (you can use 15yrs, that's what I did even though I had heard of 30+ and NAWS 20+yrs. I stuck to known users experiences)

    Can you save me money?

    Well, that's something too that hasn't been totally factored in during this debate. The Federal Residential Renewable Tax Credit allows for 30% tax credit for the price of batteries used in PV systems. For those off-grid, this is crystal clear, for those connected to the grid it is more complicated because essentially you have to use the PV electricity to recharge your batteries and not grid tie electricity. If you use 10% grid tie, you lose 10% of the battery credit, if you use more than 25% you lose the entire battery credit. And the previous statements are made with the warning that I am not a tax attorney, and this is not tax advice, this is only repeating information that is posted in various places on the Internet, and for your specific situation you should consult your tax attorney.

    But, with that 30% credit, it shifts the benefit at least somewhat to the more expensive battery. For example, if your $4000 PbA battery is an $8000 Lithium battery, the end result, IF you can take the 30% credit, ends up being a $2800 PbA battery to a $5600 Lithium battery. Thus, it isn't a $4000 difference, it is a $2800 difference. It is always nice to get the biggest credit possible.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Why not LiFePO4?
    And the previous statements are made with the warning that I am not a tax attorney, and this is not tax advice, this is only repeating information that is posted in various places on the Internet, and for your specific situation you should consult your tax attorney.
    Also from the Internet. I assume that this is what you are referencing ? Not sure what it applies to, it's about commercial developments.

    http://www.renewableenergyworld.com/rea/news/article/2013/04/irs-confirms-that-batteries-qualify-for-the-energy-tax-credit-but-imposes-limitations
    .
    "The law is clear that the components must consist of the original installation of new equipment. There is no indication that the purchase and installation of an upgrade or expansion of an existing PV system, or the addition of PV to an existing remote system, does not qualify (subject to the same requirements and restrictions as new installations)."
  • sub3marathonmansub3marathonman Solar Expert Posts: 300 ✭✭✭
    Re: Why not LiFePO4?
    Also from the Internet. I assume that this is what you are referencing ? Not sure what it applies to, it's about commercial developments.

    http://www.renewableenergyworld.com/rea/news/article/2013/04/irs-confirms-that-batteries-qualify-for-the-energy-tax-credit-but-imposes-limitations
    .
    "The law is clear that the components must consist of the original installation of new equipment. There is no indication that the purchase and installation of an upgrade or expansion of an existing PV system, or the addition of PV to an existing remote system, does not qualify (subject to the same requirements and restrictions as new installations)."

    That's the one at renewableenergyworld. Also, quoting the article, "In PLR 201308005, the taxpayer was a large solar developer that designed, financed, and installed residential and commercial solar PV systems on the roofs of buildings. In most cases, taxpayer retained ownership of these systems and either leased them to the building owner or sold electricity from the system to the building owner under long-term power contracts." So it was not only about commercial developments, it was about a large scale solar installer who did both residential and commercial installations. The article made no implication that the IRS considered the residential installations any different from the commercial installations done by this solar contractor.

    One final note is that article does not mention that limitation to the original installation of new equipment quoted by Blackcherry04.

    That quote is from http://www.absak.com/library/solar-power-tax-credits . In my opinion the quote is saying "There is no indication that the purchase and installation of an upgrade or expansion of an existing PV system, or the addition of PV to an existing remote system, does not qualify." (bold added)

    While the quote is correct, it goes on to say: "However, this issue is not yet clearly defined. For current and additional details on these requirements, contact our sales personnel." I have never heard of such a restriction, and it really wouldn't make sense, although that might not be of any factor to the IRS. If there is such a case with this limitation I would be interested to see the documentation. I could understand such a limit if for example somebody started with four golf cart batteries, after a month decided to upgrade, and ended up using the golf cart batteries back in his golf cart and still took the deduction for them. But if the batteries fail, the battery based PV system won't work at all, so it is a requirement to replace them. And when the new batteries are installed, it is "the original installation of new equipment."

    On a tangential topic, I also read it that used equipment doesn't qualify, although I thought somewhere too that was debated if the equipment had never had the tax credit claimed.
  • feedhornfeedhorn Solar Expert Posts: 103 ✭✭
    Re: Why not LiFePO4?

    My Lead-Acid experience. 5 dead sets of 4 golf cart batteries in 12 years.

    Set #1: Lasted 6 months and died due to chronic undercharging. I thought I could get away with just doing a good bulk charge off the generator each day.

    Set #2: Bought an amphour meter and learned I needed to run generator at least 8 hours a day for a full charge. And a full charge is a must. Bought a Honda 2000i to run 8 hours a day. Set failed after 3 years due to a single cell sulfaction.

    Set #3: Failed after about 2 years due to a bad jumper cable. One string was doing all the work. Bought clamp-on DC ammeter to check connections. Got tired of running generator and got 700 watts of solar panels at $6/watt.

    Set #4: Due to personal medical issue, I stayed parked and plugged in for 6 months with new batteries. Float voltage 13.6 all batteries got sulphated. Never worked right after that.

    Set #5: New batteries came with acid SG of 1.310 that was too high and they sulphated in less than two years.

    Finally got LiFePO4.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Why not LiFePO4?
    feedhorn wrote: »
    My Lead-Acid experience. 5 dead sets of 4 golf cart batteries in 12 years.


    Finally got LiFePO4.
    So you traded 220 Amp hrs @ 50% dod for 80 amp hrs @ 80% dod and your a happy camper, you probably did the right thing. Seems like you only needed 2, 6v, GC-2's to start with @ 110 amp hrs.
  • feedhornfeedhorn Solar Expert Posts: 103 ✭✭
    Re: Why not LiFePO4?
    So you traded 220 Amp hrs @ 50% dod for 80 amp hrs @ 80% dod and your a happy camper, you probably did the right thing. Seems like you only needed 2, 6v, GC-2's to start with @ 110 amp hrs.

    Actually 2 GC batteries wouldn't do the job for me cause they wouldn't put out enough current to run my microwave. The LiFePO4 will do the job.

    And, over the years I learned to use less power. LED lighting, more efficient laptop and other little details. I average only 50 ah from the LiFePO4 per day now.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Why not LiFePO4?
    feedhorn wrote: »
    Actually 2 GC batteries wouldn't do the job for me cause they wouldn't put out enough current to run my microwave. The LiFePO4 will do the job.
    I doubt they would in the condition that you described they were in. I am sure that LiFePO4 have issues when they become unhealthy or close to end of life.

    Now this may be a whole new issue, Does a LiFePO4 battery have the ability to release stored current faster than a Deep Cycle Battery ??

    @ 12 V , how many amps does your microwave pull and what is it's watt size ??
  • PhotowhitPhotowhit Solar Expert Posts: 5,653 ✭✭✭✭✭
    Re: Why not LiFePO4?
    feedhorn wrote: »
    My Lead-Acid experience. 5 dead sets of 4 golf cart batteries in 12 years.

    WOW! That's ugly! I might have looked at other possibilities as well, In my 14 years running an off grid system here, I've only had 3 sets, and I did kill one of those, though it was near/past the end of it's cycle. Mostly setup and ignored! I did check SG often(weekly or every other week) when I was torturing the batteries (GC2s) running them past 50% often during the summer months running an A/C.

    I would suggest that you could have benefitted by a 30 minute talk with someone who had lived with battery maintenance. I don't do generators(other than solar panels) but would see problems with many of these.

    Without a discussion of loads/needs, 8 hours of charging from a genny, seems excessive, unless you were charging at a very minimal charge rate or running your batteries down a great deal.

    In a mobile application, you need to check connections regularly. I suspect you now do check your connects.

    Batteries like to be used,

    You know what you did to the last set.

    If your LifePo4 batteries are less susceptible to problem with heat, then that will help with RVs as well, I would ask about the temp of mobile RV batteries. I've seen that as a problem. Looks like you dumped your Honda 2000i, they are great units. Hope your 6300watt is half as reliable and quiet!
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Why not LiFePO4?
    feedhorn wrote: »
    My Lead-Acid experience. 5 dead sets of 4 golf cart batteries in 12 years.

    Set #1: Lasted 6 months and died due to chronic undercharging. I thought I could get away with just doing a good bulk charge off the generator each day.

    Set #2: Bought an amphour meter and learned I needed to run generator at least 8 hours a day for a full charge. And a full charge is a must. Bought a Honda 2000i to run 8 hours a day. Set failed after 3 years due to a single cell sulfaction.

    Set #3: Failed after about 2 years due to a bad jumper cable. One string was doing all the work. Bought clamp-on DC ammeter to check connections. Got tired of running generator and got 700 watts of solar panels at $6/watt.

    Set #4: Due to personal medical issue, I stayed parked and plugged in for 6 months with new batteries. Float voltage 13.6 all batteries got sulphated. Never worked right after that.

    Set #5: New batteries came with acid SG of 1.310 that was too high and they sulphated in less than two years.

    Finally got LiFePO4.

    Of these only the last one is the fault of the batteries, and that not of the lead-acid nature. You could easily have trouble with the LiFePo units as well.
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Why not LiFePO4?

    LiFePO4 batteries can surge C*1 to C*3 or so (from what little I have read)i... much better than lead acid.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Why not LiFePO4?
    BB. wrote: »
    LiFePO4 batteries can surge C*1 to C*3 or so (from what little I have read)i... much better than lead acid.

    -Bill
    Deep Cycle definitely have a dip and recover on the voltage side, can't say the current has that big a drop. It can be mitigated somewhat with the cable selection. It's a test that could be ran for abut $1500 or so, I am out of R & D funds at the moment. My Microwave ( 1,500 watts ) pulls about 180 amps @ 12 V, with out knowing all the specifics of each component in a system and duplicating it, it's all speculation. Some of the hardware on the LiFePO4's don't look like they could take over 200 amps.
  • feedhornfeedhorn Solar Expert Posts: 103 ✭✭
    Re: Why not LiFePO4?
    Photowhit wrote: »
    WOW!Looks like you dumped your Honda 2000i, they are great units. Hope your 6300watt is half as reliable and quiet!

    The Onan LP generator is OK, it will run both my air conditioners if needed. So far in 8 months using the LiFePO4 I've only had to run the generator on one very cloudy day. Now I never need to run the generator for more than one hour to completely recharge the battery.

    Every week or so I run the generator just to stand in amazement and watch the LiFePO4 accept a 75 amp charge rate even when its already charged to 95%.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Why not LiFePO4?
    I am out of R & D funds at the moment.

    Yeah, me too.
    But we did prove something, eh? Even if it can't be released/explained.
    Mine have been working better since the charge rate adjustment but I still can't 'prove' it beyond anecdote due to lack of funding. Can't even do the temperature check.

    (Never mind, guys; BC knows what I'm talking about.)
  • ReedReed Solar Expert Posts: 55 ✭✭
    Re: Why not LiFePO4?

    As Feedhorn has noted, LFP charge rapidly and almost linearly to absorb. The charge rate in battery bank has been basically the same as the wattage from generator/line power the few times we have done such. We only charge through battery charger with 15 amp cord (1500 W more or less) or a 1 kW generator. We charged from -3000 W-hrs to absorb in two hours with 15 amp cord.

    Have noted earlier that son installed the battery chargers since we have traveled extensively in Mexico and there “dirty power” is commons. Son checked the voltage at beach site in Yucatan and it rapidly bounced 85 to 145 V (or thereabouts)

    It might be simpler to give energy storage in W-hours since folks discuss 6 V, 12 V, 24 V (the apparently excellent fork lift battery bank), and 48 V (our system among others). Cariboocoot always signs off with
    Power Formula: Watts = Volts * Amps

    I am a retired physicist and always preferred volts and watts even though amperes are a major building block of the International System of Units “…The constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 m apart in vacuum, would produce between these conductors a force equal to 2×10−7 newtons per metre of length”

    Reed and Elaine
  • feedhornfeedhorn Solar Expert Posts: 103 ✭✭
    Re: Why not LiFePO4?
    Reed wrote: »


    Power Formula: Watts = Volts * Amps

    I once tried to work only in watts but alas measuring instruments just measure volts and amps. I gave up went with the flow of the amps.
  • ReedReed Solar Expert Posts: 55 ✭✭
    Re: Why not LiFePO4?

    Our monitors give us information in volts, watts, and amps. The amps given are for 48V 1 amp is the same as about 4 Amps for a 12V system. A few folks will state their amp-hours by adding up the amp-hours for their bank of 6V batteries and not the equivalent as a 12V system.
    Reef
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Why not LiFePO4?

    Watts are best used when one of the factors is fixed, such as with 120 VAC (RMS). DC systems vary in Voltage and current so it is usually necessary to use the terms separately in order to understand what is going on (wire and over-current protection sized by Amps, for example). When dealing with batteries Amp hours capacity is used because the Voltage is nominal and the real capacity varies with the current draw, so neither factor is fixed. Even with AC it is sometimes better to disregard Watts and use Volt Amps so as to include the power factor of the load vs. the supply capacity.
  • ReedReed Solar Expert Posts: 55 ✭✭
    Re: Why not LiFePO4?

    China Aviation Lithium Batteries (CALB) makes battery banks for home/EV use from 3 kW-hours to 200 kW-hours. Might be a tad expensive for 200 kW-hours.

    Or you can just buy submarine battery banks "... FIVE-FOOT HIGH Nuclear Submarine Batteries are very conservatively designed to outlast the lifetime of a submarine boat, (35 years). One of the great improvements is the use of calcium in the very thick oxide-lead positive plate. This allows low gassing during charging, which results in only adding water once every two years, and much lower charge loss, due to charge migration during stand-by. We estimate for home use you will get 35 years or better with good care. Each cell is 2.0 volts per cell X 7000 amps = 14,000 watt hours, a 12 volt system = 6 cells X 14,000 watt hours= 84,000 watt hours,

    Probably a tad expensive as well. I was impressed with the consideration of fork lift batteries but these submarine batteries are probably all one would ever need.
  • ramlouiramloui Solar Expert Posts: 104 ✭✭
    Re: Why not LiFePO4?

    My current FLA bank (24 V, 430Ah) is only 18 months old and meeting my needs. But when it dies, I will certainly consider alternatives. I tried googling for LiFePO4 batteries but all I come up with is small capacity units, about 100Ah.

    Can anyone point me somewhere that could supply the equivalent of 430-600Ah @ 24V? I would like to educate myself on the application.
    Off-grid cabin in northern Quebec: 6 x 250 W Conergy panels, FM80, 4 x 6V CR430 in series (24V nominal), Magnum MS4024-PAE
  • sub3marathonmansub3marathonman Solar Expert Posts: 300 ✭✭✭
    Re: Why not LiFePO4?
    PNjunction wrote: »

    I'm afraid however that the signal to noise ratio is already so high in this thread, that any objective discussion about lifepo4 is moot, and lurkers have long since vanished.

    It happens not only here, but in nearly all other forums too. Sad really.

    Wait!! Don't go yet!! I'm lurking!! Maybe SOMEBODY here can help me figure out what to do, as I am in this exact dilemma. I'm willing to switch away from PbA, and had hoped to years ago but the economics didn't seem to be there yet. I'm thinking it is much closer, if not possibly even better, now.

    The parameters are that I want a 600ah battery bank for an XW6048. I would be OK with more, as more is always better. :D I'm hoping, one day, to take this part off-grid, so I could add much more grid tied PV. I know, it's highly questionable and might not ever get done. I suppose I could get by again with the 357ah battery bank as I have/had, but the choice for those batteries was based more on what I could get locally at the decent price in a 12V battery. Now I'm willing to put 2V cells together myself if they are a better choice.

    I am thinking that, although some have said I killed my original batteries, the autopsy will show I'm innocent. But I believe I can keep a high quality PbA bank, or a high quality Lithium bank, or even the Nickel-Iron or Sodium Ion going.

    It seems that Nickel-Iron is out, based on the cost and the end of life electrolyte disposal questions. But maybe I could be proven wrong about them.

    Sodium Ion is still in the running, but it is very expensive. The benefits are it is a sealed system, so no maintenance adding water or anything else. I think they sound fantastic, but I wouldn't be able to afford the 600ah bank, I'd be lucky to get to 300ah. I still haven't figured out if they could handle the required parameters.

    The Lithium batteries are very interesting. They would take up so much less space. I could move them myself. But they are more expensive, although if they are treated correctly I believe they will last twice as long. It's the "if they are treated correctly" part that is scary, as one mistake can burn of $8000 of batteries in 5 minutes. Also, if you have to buy $2000 worth of battery monitoring system, that is an added part of the battery price, not a long term investment over 50 years worth of Lithium batteries. One other benefit is that instead of 24 cells to maintain, I'd only need 16 to have a 48V system.

    The PbA batteries are the standard. Incredibly heavy, bulky, and require at least semi-weekly maintenance (in the summer) of checking water levels, and doing the equalization procedure when necessary. However, as long as you're at least halfway able to follow the rules, the batteries will perform admirably. The other problem with the PbA batteries is do I go with Forklift Batteries, or get another batch of the same brand I've had if the company comes through and stands behind their product.

    Now, I'm of the same thinking as Photowit said in Post #62, "All I see is pure Economics... If it's my money for my use... I want to save money... Save me money and I will buy your product!!!"

    So I'm hoping that it can be figured out, on a purely economic basis, based on a realistic cycle life of 30% DOD, what is the best battery.
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Why not LiFePO4?

    With Lead Acid Batteries, the rules of thumbs were weighted towards larger AH battery banks, because (in my humble opinion):

    1) Larger Bank to sustain larger charging currents/shallower (on average) discharges because we only have 4-8 hours of "useful sun" per day
    2) Larger Bank to sustain higher surge currents (C/2.5 max surge, 100 AH @ 48 volts per 1kWatt of inverter/solar array and such).
    3) Larger Bank to prevent discharging below 50% for longer (in general) battery life.

    With other chemistries--Some of these rules of thumbs change. For LiFePO4 batteries, there is no "absorb" time needed. So you don't need to finsh bulk charging by noon so you have have 2-4 hours of Absorb (fixed charging voltage and slowly declining charging current). Instead, you can dump maximum array current (or generator/utility current) as available into the battery bank (C*1 or even more). So, smaller battery bank (AH) and potentially smaller solar array because "all" array current is available for charging (if you run loads when the batteries hit absorb/float--then you are still using most the array output anyway).

    And for the solar array, if flooded cell Pb is ~80% efficient and Li ~100% eff--That gives you another -20% smaller solar array (more efficient battery bank).

    Surge--With C*1 or even much larger surge currents available, you almost do not need to size the battery bank for surge loads (well pumps, refrigerators, etc.)--Just wiring.

    AH of Lead acid vs LiFePO4--This is where I am not sure that a hugely smaller bank is always possible for Li batteries.

    If we look at lead acid's "useful" storage range as 50% to 85% -- 35% of AH capacity. And LiFePO4 as 20-80% or 60% of capacity, then we would see:

    35% Pb / 60% Li = 0.58x smaller AH battery bank for "pure" Pb vs Li based on usage.

    Now--"real life"... Running a true deep cycle battery below 50% on occasion is not going to "kill" the battery. So--You got somewhere upwards of 30% of capacity "in reserve" for times when the generator does not start, spouse/kids at home and don't know what to do, etc...

    If you run the Li battery down to 20%--You are close (how close?) to having to throw the kill switch/fiire up the backup to the back AC generator for power.

    If you go "too low", you do run the risk of permanent Li battery damage (although, very low rate of charging current 1/100 or 1/1,000??? can save your cells)--It is something that will not be done automatically (at least at this time)--So there is the panic of trying to configure some sort of low amperage charging (or buying a cheap adjustable charger/power supply to keep on the shelf for such an emergency). Not fun--But certainly possible and perhaps practical for a DIY person.

    I am pretty close to saying (in my humble opinion) that a Li vs Pb battery bank can be close to 50% of the AH rating for most people as they use the systems today with our standard rules of thumbs (basically, 2 days of storage). And for those people with high peak loads, and very low average loads, even a 1/4 size AH Li battery bank would be very possible vs Pb (microwave, well pump, no sustained loads like fridge which simply require AH storage to meet the 2 day goal).

    The other Li issues (Battery Management, checking cell balance)--From those that have experimented with Li banks here on Off Grid applications (not electric car, R/C cars and planes, etc.)... It sounds like most balance issues are not an issue and a scheduled check with an accurate Fluke meter and a hand full of light bulbs+battery clips can bring cells back into balance when/if needed.

    The last questions (for me), are people really going to get 10+ years from these cells in Off Grid applications with "normal real person maintenance) and how they will perform at extreme temperatures (over 95F and well under freezing)--I am sure the information is there--I just have not really looked into that stuff just yet.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • solar_davesolar_dave Solar Expert Posts: 2,382 ✭✭✭✭
    Re: Why not LiFePO4?

    Temps play a critical role in LI battery technology. To get long life the average temp must be controlled to pretty much human comfortable temps. An example of problems encountered can be seen with the Nissan Leaf in Phoenix, where they lost upwards of 30% capacity in the first year of operation. Nissan ended up buying many of those cars back.

    Now on our Chevy volts active cooling, literally running the AC compressor to chill coolant pumped through the battery, has resulted in the same range numbers after 3 years of use. Also really cold temps don't work out well for LI batteries, in fact the Volt will heat the battery off the ESEV charge adapter to keep the battery temps up in extreme cold using the same coolant loop. If left with a low SOC and long cold soak, the Volts will refuse to run after a couple days in extreme cold.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Why not LiFePO4?

    It would be good to see someone step up and buy a 600-800 amp hr bank @ 24 v that is cycled to 50 % on a daily basis and let us all in watching it's progress. A 100 amp hr battery will hardly be realistic on the performance one could expect. There is chatter everywhere, but little hard facts other than the price.
  • ReedReed Solar Expert Posts: 55 ✭✭
    Re: Why not LiFePO4?

    Sub3marathonman - if guilty you were only following orders. There is still a lot of confusion between the higher energy density LiCo batteries which I believe Tesla and others have used. These have stricter regimes of operation than does LFP

    Blackcherry - Liberty Coaches has stated that they cycled quite large LFP banks (1400 or more amp-hours at 12 V) to more than 80% DOD for over 2000 cycles. According to their press release "...Since Liberty Coach has continually set the benchmark for technological advancements, it should come as no surprise that we have continually installed this technology since January 2010 and can report that the batteries should easily keep the systems alive for the documented 2000 cycles, which could easily be 10 years or more. This translates to a significant reduction of battery replacement.." At $1.8M and up for coaches, I guess they wanted to be sure. I am most certainly not in the market for a high end Prevost.

    We have been cycling to 30 and 40% for a year now with a 720 amp-hour battery bank (12 V nominal). However, we seldom go below 20 or 30% unless we are running air conditioner or running. It is set as a 180 amp-hour 48 V nominal battery bank.

    Googled a few sites on LFP and got the following for LFP

    Charge temperature 0 to 40 C, 32 to 102 F
    Discharge temperature -10 to 60C, 12 to 140 F

    This may require a light bulb in the bay in which the battery bank is emplaced to keep it above freezing point. It will have to be a very warm day for us to be where it is 102 in the shade for charging - and we plan never to be in a place where it is 140F in the shade ever. We do open the panel over the front bay (where the battery bank resides) when the system is charging or when the inverter is running.

    There are a number of fabricators of lithium batteries. I write fabricator since I believe the cells themselves are all made in China. I know of two: Manzanita which we have and Lithionics which Rob Jones (the first guy to have an LFP system developed for his personal vehicle). Both of us have been quite satisfied and Rob is on his third year. He wrote that he is thinking of getting a more modern motor home. He gives a lot of seminars at rallies on solar and lithium.

    Manazanita Micro fabricates for electronic vehicles and has done well. We have four of the 180Ah packs. Includes:"... 4 Lithium Ion Cells, Aluminum Battery Box, Lexan Top, Fully Assembled Reg Deck, All necessary hardware, and Regulator.."

    The battery box is 8" wide, 12.5" long, 13.5" tall (without lugs). Total weight with 180Ah cells is 63 lbs/ 28.5 kg. $1564

    Lithionics now fabricates lithium battery packs designed for solar but they are quite a bit more expensive.

    PNJunction is apparently incorrect for once, the thread has continued

    Reed and Elaine
  • SwanneySwanney Registered Users Posts: 8 ✭✭
    Re: Why not LiFePO4?

    Hello all,
    If you are thinking of making the change to lithium batteries I've attached a link that helped sway me in that direction. It's a big leap of faith considering the price and not suited to every situation.
    I run sinopoly LIFEPO4s, 24v 300ah in an off grid house. 1080watts of pannels and outback MX60 solar controller. The batteries have been in for 2 years now and I LOVE them. No BMS. Monitor individual cells with a cellog8 and state of charge with a votronic battery monitor. I've monitored cell ballance closely over the past 2 years and there has been negligible drift. Hope this article helps.

    http://marazuladventures.files.wordpress.com/2013/01/diy-lithium-iron-phosphate-batteries8.pdf
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