Why not LiFePO4?

Just wondering why none of the major solar suppliers are offering LiFePO4 battery cells.

They are in the price range of AGMs but appear to have much greater potential.
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Comments

  • feedhornfeedhorn Solar Expert Posts: 103 ✭✭
    Re: Why not LiFePO4?

    There is still more profit in lead batteries right now.

    LiFePO4 last too long and have too much bang for the $.
  • Ks SolarKs Solar Solar Expert Posts: 47 ✭✭
    Re: Why not LiFePO4?

    You may be right but it is all about cost. Period. If people have to pay a nickel more up front. Doesn't matter if LifePo4 will get them 2000 cycles compared to 1000 for agm. It really depends how you treat them too. Amg is still lead acid. It lends itself to a slow /low amp draw. Lithium can dump major amps fast but you have to treat it right .. Ex= Boeing 787 batteries catching fire...
  • PhotowhitPhotowhit Solar Expert Posts: 5,653 ✭✭✭✭✭
    Re: Why not LiFePO4?

    Lots of reasons;

    Not really 'proven' technology, lots of things going right, but Nissan's Leaf problems, Boeing's problems come to mind.

    I 'invested' more upfront in a forklift battery for it's longer life cycle, 15-20 years, is very realistic and others have gone longer, though in my opinion, likely on the diminishing capacity.
    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.
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: Why not LiFePO4?
    gpearce52 wrote: »
    Just wondering why none of the major solar suppliers are offering LiFePO4 battery cells.
    They are in the price range of AGMs but appear to have much greater potential.

    They're starting to be available in Europe:
    http://www.solaxpower.com/product/battery-system-for-hybrid-inverters/
    http://de.krannich-solar.com/produkte/speicherloesungen/lithium-ionen-batterien.html (German)
    http://www.sma.de/en/products/solarinverters/sunny-boy-3600-5000-smart-energy.html
    http://www.victronenergy.com/batteries/lithium-battery-24v-180ah/
    http://www.phonosolar.com/en/Phonocube.html
  • Core2QuadCore2Quad Registered Users Posts: 6
    Re: Why not LiFePO4?
    gpearce52 wrote: »
    Just wondering why none of the major solar suppliers are offering LiFePO4 battery cells.

    They are in the price range of AGMs but appear to have much greater potential.

    Because no large well established company is making LiFePo4 cells. Almost all companies making LiFePo4 cells (besides A123 Systems, that went bankrupt and was sold to the Chinese) don't have that much experience yet, and do not have a proven track record. They are somewhat "unknown." I sell Li-ion cells/packs for a living, and can tell you that I've seen way more quality issues with LiFePo4 than I have with other Li-ion chemistries. One of the other problems is Li-ion cells in general do not like being held at a high SOC (state of charge). Lead acid batteries love being floated at high voltage levels, where the Li-ion chemistry in general prefers to hang around 20-40% for the longest cycle life.

    If you go on some of the DIY EV forums, you'll find some people have had many quality issues with larger prismatic LifePo4 cells. Some of them died or performed very poorly, and then you get to deal with an overseas Chinese company.

    Also one of the reasons LifePo4 hasn't taken off is the lack of quality chargers, battery management systems, compatible inverters and general acceptance in the RE industry. I think LiFePo4 could take over a large segment of the market in the next decade, however I think some of the more experienced battery companies will have to take lead and further refine the technology.

    Also Li-ion cells in general are more sensitive and require more electronics and wiring in order to be setup correctly. In Lead acid battery banks cells are linked together in series and or parallel and then fed into an inverter. With Li-ion's you need to monitor the voltage at the individual cell level (3.2v in the case for LiFePo4). So you need a special balancing charger to insure that one individual cell is not overcharged. If a pack becomes out of balance and no balancing circuit is in place this can lead to a cell venting and possibly exploding. Then you need a form of overdischarge protection and also overcharge protection to protect the cells. Taking a Li-ion down to a low voltage can render it useless in even a single instance in some cases. So in most Li-ion applications there is a monitoring circuit often called a BMS (battery management system). Then there are mosfets which are solid state relays which turn off the flow of electricity in the event of an overcharge, overdischarge or short circuit situation. So as you can tell, it becomes a decent amount more complicated.
  • feedhornfeedhorn Solar Expert Posts: 103 ✭✭
    Re: Why not LiFePO4?
    Core2Quad wrote: »
    So as you can tell, it becomes a decent amount more complicated.

    I changed over to LiFePO4 because over the years I began to hate the very nature of lead-acid batteries. Everything about them pissed me off. I had waited for years for anything that would get me away from lead and finally the safe and sane LiFePO4 became a reality. Took me two full months of careful study and experimentation to fully understand LiFePO4 batteries. That was a lot of work but now after 8 months of daily cycling use, I will never go back to lead-acid no matter what my LiFePO4 batteries do. They could fail tomorrow and I'd just buy a new one and go for another 8 months of battery joy. Actually, I expect them to last 10 years or more with no maintenance. I learned to Love my LiFePO4s in just 8 months.

    Its the little details that mean the most to me: The stable 1 volt higher than lead acid. The stable high current output to run my coffee pot and microwave. The 99% efficiency. The super fast recharge time if I need to run the genny. So Nice !! And well worth the extra cost of complexity. Once setup right all the complexity is just invisible.
  • ReedReed Solar Expert Posts: 55 ✭✭
    Re: Why not LiFePO4?

    Feedhorn

    We seem to be in the same boat in a sea of naysayers: folks that confuse different lithium chemistries and folks that worry about battery management systems.

    Our son who has been in commercial alternative energy for 23 years designed and fabricated our current system. We are basically solar autonomous:
    1420 W of panels, 9.6 kW-hrs of lithium iron phosphate, 4.0 PSW Magnum inverter. Since son designs and fabricates commercial (just put in a 1.8 megawatt system for power company), he runs power from panels to controller at high voltage. The six panels are ganged in two sets of three in series so the power goes to controller at around 90 V. We have gotten up to 1300 W to MPPT-45 controller and this is only around 14 amps.

    We run micro-wave to save propane and utilize the inverter to run Dometic refrigerator during daylight hours (and 24 hours a day if we know we shall have full solar insolation on the following day). We have run the air conditioner for up to 3.5 hours on solar/battery but generally just run it for an hour in the evening off batteries to cool the cabin down to 85 or less.

    We had problems in Mexico (with older system that had 700 W of solar and 4 glass mat batteries) with "dirty" power. We lost a micro wave in Baja and Yucatan from this. Son and family came down to spend a week on beach in Yucatan and installed a battery charger. This doesn't care if voltage bounces from 80 to 145 V and is what we use in the few times we do hook up. This means we have tossed 50 amp cord and use only a 15 amp power cord. When we have tied up to power (when we were in an RV park with heavy shade) and were down -3000 W, the 15 amps had us at absorb in less than two hours (at 15 amps).

    Reed and Elaine (fulltime Offgrid RV'ers most of the time - except when we are near a large city visiting relatives and boondocking is not terribly viable)
  • PhotowhitPhotowhit Solar Expert Posts: 5,653 ✭✭✭✭✭
    Re: Why not LiFePO4?

    You are both full time RV'ers, the weight savings will make lithium Iron more attractive to you, Ask your son if he would have used lead acid or Lithium Iron in a fixed location on a cost basis.
    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?
    Photowhit wrote: »
    You are both full time RV'ers, the weight savings will make lithium Iron more attractive to you, Ask your son if he would have used lead acid or Lithium Iron in a fixed location on a cost basis.

    Oui.
    In a fixed location application just mentioning the 3X price of an equivalent LiFePo bank will cause the prospective buyer to stop listening altogether. People are willing to pay a little more for some demonstrable advantage, but not a lot more.
  • feedhornfeedhorn Solar Expert Posts: 103 ✭✭
    Re: Why not LiFePO4?

    You can't make bullets out of Lithium!

    In the coming Global Economic Collapse most lead will go to bullets for all the civil wars.

    After some 20 years LiFePO4s will probably still have 50% capacity where no lead or your dead.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Why not LiFePO4?
    feedhorn wrote: »
    You can't make bullets out of Lithium!

    In the coming Global Economic Collapse most lead will go to bullets for all the civil wars.

    After some 20 years LiFePO4s will probably still have 50% capacity where no lead or your dead.
    Guess who has the major amount of the Lithium, The majority of known lithium reserves are located in China.
  • feedhornfeedhorn Solar Expert Posts: 103 ✭✭
    Re: Why not LiFePO4?
    Guess who has the major amount of the Lithium, The majority of known lithium reserves are located in China.

    Guess where the most prolific Lithium Mine is? Silver Peak, Nevada.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Why not LiFePO4?
    Photowhit wrote: »
    .. Not really 'proven' technology, lots of things going right, but Nissan's Leaf problems, Boeing's problems come to mind.

    Oh no, not THIS again.

    Nissan - not using lifepo4 chemistry. Boeing - not using lifepo4 chemistry. In both cases NOT OUR APPLICATION.

    Lifepo4 is great, but the ONLY INFORMATION about it comes from OUTSIDE our application, and typically not even the same chemistry. Most consumers don't know the difference between li-ion chemistries.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Why not LiFePO4?
    Core2Quad wrote: »
    Because no large well established company is making LiFePo4 cells.

    Tell that to GBS, Winston, CALB, etc. :)
    Almost all companies making LiFePo4 cells (besides A123 Systems, that went bankrupt and was sold to the Chinese) don't have that much experience yet, and do not have a proven track record.

    Yeah, A123 are HIGH-RATE lifepo4 cells, and are NOT THE ONES we use with a solar housebank. Their business dealings do not apply to us since we don't use them.
    They are somewhat "unknown."

    Don't tell that to the marine guys who have been using them for solar house-banks for more than 5 years now.

    You know, I don't know what to say about all the FUD you are posting about them. It is adamantly clear that you have no experience with they types of cells we use, such as CALB, GBS, Winston, and the like.

    The biggest problem with either cheerleaders or naysers of lifepo4 come mostly from the experience of RC-modeler's, or merely repeating what they "read" about EV use.

    While I don't like to cross-post forum threads, how about this from someone who deals with it daily and how simple it really is to charge and maintain:

    http://www.solarpaneltalk.com/showthread.php?17609-Simplified-lifepo4-charging-and-care

    All the rest is just second-hand FUD. What I BEG people to do, is get FIRST-HAND experience with them, and not just rehashing wive's tales or repeating abusive use patterns.

    Let us please not get into another boring debate about it. Lifepo4 care and charging is easy. However, there is a lot of money to be had from the unknowledgeable that can be scared into hanging a rat's nest of wires all over the place.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Why not LiFePO4?
    PNjunction wrote: »
    Most consumers don't know the difference between li-ion chemistries.
    They probably don't care one way or the other once they find out the price.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Why not LiFePO4?
    Photowhit wrote: »
    You are both full time RV'ers, the weight savings will make lithium Iron more attractive to you ...

    Don't overlook the fact that there is NO sulfation to worry about, thus a PSOC or partial-state-of-charge environment is not a problem whatsoever for lifepo4. Not having to charge fully is a great feature for solar users, as long as you have the capacity to finish the job daily.

    In fact, a "full charge" is actually set by the user. There is no need to obtain 100% SOC, EVER, so that makes it a great fit for solar. That alone may justify the upfront cost operationally, where you might quickly kill a lead-acid bank and have to replace it again and again.
  • PhotowhitPhotowhit Solar Expert Posts: 5,653 ✭✭✭✭✭
    Re: Why not LiFePO4?
    They are somewhat "unknown."
    PNjunction wrote: »
    Don't tell that to the marine guys who have been using them for solar house-banks for more than 5 years now.

    Well, you see, you proved the point, I will not tell you that my forklift/traction battery will last 20 years, based on my 4 years of use. I can point at reputable sources like NAWS who say they have had 20+ years use from them....

    I do apologize for mixing chemistries, I did think the original Leaf battery was some lithium iron type, but I did not / have not followed up on that.
    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.
  • PhotowhitPhotowhit Solar Expert Posts: 5,653 ✭✭✭✭✭
    Re: Why not LiFePO4?
    PNjunction wrote: »
    In fact, a "full charge" is actually set by the user. There is no need to obtain 100% SOC, EVER, so that makes it a great fit for solar. That alone may justify the upfront cost operationally, where you might quickly kill a lead-acid bank and have to replace it again and again.

    This is an advantage, until it isn't, a forklift/traction batteries 80% usable capacity duplicated in a lifepo4, would cost a huge order of magnitude, I have an 800amphour 24 volt traction battery with about 680 AmpHour usable capacity. For the same capacity in a lifepo4 battery if 100% is usable capacity would cost?
    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?

    Whoa, guys.

    A lot of lead-acid batteries dropped dead from abuse before anyone figured out how to best use them in an RE application. I think some of the people that build them still don't know. :p

    So far the LiFePo shows promise for RE, but the cost is shutting people down so there aren't a lot of people getting that much-needed first-hand experience. We still need pioneers to take the plunge and learn the tricks and help bring the price down. Time was when anyone with an RE system was a pioneer. Now the application is much more mainstream, but that does not mean more people are going to try new technology. Quite the opposite in fact.

    Even though I probably still qualify as a pioneer I couldn't possibly justify the price despite the advantages. Maybe I'm turning into a stick-in-the-mud but having to fix systems all the time makes me want to go with off-the-shelf-it-works designs and not experiment.

    *sigh* I guess I've lost that adventurous spark of youth. About 30 years ago.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Why not LiFePO4?

    We're cool.

    I try my hardest not to cheerlead lifepo4 so that everyone needs to replace lead with lifepo4, or that is fits in all applications.

    I just get frustrated when I see straw-man arguments coming for those with no first hand experience, relying solely on those from outside our application. Typically these outside application users are abusing their batteries, have something to sell, or swayed by marketing agendas.

    An analogy would be me, who has no first hand experience with Rolls-Surrette batteries, trying to guide another in the fine points of EQ'ing them.

    I promise to be nice....
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Why not LiFePO4?
    Photowhit wrote: »
    This is an advantage, until it isn't, a forklift/traction batteries 80% usable capacity duplicated in a lifepo4, would cost a huge order of magnitude, I have an 800amphour 24 volt traction battery with about 680 AmpHour usable capacity. For the same capacity in a lifepo4 battery if 100% is usable capacity would cost?

    Wow - that would be about 11.8K$ for bare cells alone if I did my math right with 200ah bare cells configured. (I'm not an advocate of external balancing when charged properly) I'm quite sure your forklift battery costs far less! In fact, since you don't take these below 80%, you'd need a bit more. But no solar user is going to drive them further than 50% DOD for autonomy reasons.

    http://elitepowersolutions.com/products/index.php?cPath=25

    But now we are talking apples and oranges. You will never be moving your forklift battery. I can build this sucker on the kitchen table, never rent a forklift, and can haul it in the back of my sedan (maybe.) . I'll never have to achieve 100% SOC, ever. As long as my solar array is reasonable, I can afford to play "catch up" on good days, whereas your forklift battery might be sulfating in a deficit charge scenario.

    That PSOC characteristic is the real reason I fell in love with lifepo4. It is the opposite of lead - the worse you treat it, (staying within voltage limitations of course), the longer it lasts! :) This is actually a problem, because there is no penalty for psoc, you may be tempted into taking them into strange scenarios, not just daily cycling. In that case, one must still be on the alert for bad power-budget calculations and not stick their head into the sand. :)

    Thing is, we've been over it before and can pick these apart to death. I have no problem with people sticking to lead and replacing them. If the cost is out of budget *up front*, then so be it.

    I dream of the day when I have power needs that require an $11K lifepo4 battery bank. That means I have a yacht to properly house it in!
  • feedhornfeedhorn Solar Expert Posts: 103 ✭✭
    Re: Why not LiFePO4?

    I paid $610 for my 100ah LifePO4 see here:

    http://www.batteryspace.com/lifepo4-prismatic-battery-12-8v-100ah-1-28-kwh-10c-rate---un38-3-passed-3-2vx4-dgr.aspx

    Thats just a little more than the 4 golf cart batteries that it replaced. They went bad in only a bit over two years.

    I now have more peak current, less voltage droop, and faster recharging than ever before and expect them to last 10 years.

    Paid about $100 for my BMS system.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Why not LiFePO4?

    Nice. Mine are the smaller 20 and 40ah versions, without any bms, other than an external LVD which I'm about to review later (Powerwerx ITS-12). Stay tuned.

    I don't charge them any greater than 13.8 to 14.0v, so I have plenty of headroom for balance, which is not something I obsess over as long as they are reasonably the same and no cell goes higher than 3.6v. My personal LVD is 12.8v (3.2v per cell) or a little under like 3.175v, so that I don't have to limit my initial recharge current (like 0.01C until 3.2v is reached again), by not taking them far down the discharge knee. I still get about 80% DOD from them that way.

    They make great exploratory batteries for those interested. Or similar Winstons or Calb's. I just wish I could record the "aha moment" from others when they happily go beyond 50% SOC with full performance, even though I don't take them beyond that. It's just a kick in the pants to actually experience. :) I know you probably did!
  • PhotowhitPhotowhit Solar Expert Posts: 5,653 ✭✭✭✭✭
    Re: Why not LiFePO4?
    PNjunction wrote: »
    ... You will never be moving your forklift battery...
    "Give me a lever long enough and a fulcrum on which to place it, and I shall move the world." - Archimedes

    I believe it was May 7th and 8th 2013, just me, a few leavers, a ramp, a 5x8 trailer, and some frustration to work out, took about 3-4 hours to slide it about 10 feet into the trailer and about 4 hours to set it on a platform about 12 feet, sorta around a corner. More impressive is I towed it to it's new home 9 miles away with my Toyota Echo, battery and trailer weigh nearly as much as the car!

    I run an A/C daily and will at need take it down to 20% SOC but only once a couple times has it been down nearly that low, and actually never in summer. I don't use a back up generator, so the capacity is important to me.

    I do thank you for exploring the new technology, I purchased my first solar panel when it cost about $10 a watt, so there may well be a new technology battery in my future if I live long enough, plan to get 15 years out of this battery and we'll see where the technology has taken us.
    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.
  • ReedReed Solar Expert Posts: 55 ✭✭
    Re: Why not LiFePO4?

    Wondered what the deal was with fork lift batteries. So I googled the subject and wow, they weigh several thousand pounds. They would be excellent for home use but not for an RV, which is where Feedhorn and I are coming from

    PNJunction - thanks for post a month or so ago that got me from being so OCD with the LFP SOC. We are in an RV Park and to much shade for solar, so I just let them go down till they are below -3000 W and then hook up the 15 amp power cord to battery charger and things are up to -1000 W in an hour and a half or soast
    Reed
  • sub3marathonmansub3marathonman Solar Expert Posts: 300 ✭✭✭
    Re: Why not LiFePO4?
    Photowhit wrote: »
    This is an advantage, until it isn't, a forklift/traction batteries 80% usable capacity duplicated in a lifepo4, would cost a huge order of magnitude, I have an 800amphour 24 volt traction battery with about 680 AmpHour usable capacity. For the same capacity in a lifepo4 battery if 100% is usable capacity would cost?

    Maybe this is ridiculous, but I'm wondering if anybody ever took into consideration the recharging cost comparison between the li-ion and the PbA batteries. I'll let the experts correct the following theoretical situation if the assumptions are off, and probably the example is a bit extreme, but the figures have been previously presented as a point of debate. I also thought if the forklift batteries were cycled to 80% DOD they would be used up in about 1500 cycles, and the li-ion would be able to do maybe 3000 cycles at 80% DOD, so that is another variable that is in the equation but overlooked here.

    In the 680 usable ah @ 24V scenario, that would be about 16kwh / day that would need to be recharged. Over the 20 year lifetime of the batteries, that is 119,000 kwh that need to be recharged. If the PbA batteries end up 60% efficient (I think Bill says 50%, and Rolls has what seems to me 42%), that would mean you have to put in 198,000 kwh of recharge. I thought the li-ion was around 90% efficient, which would end up at 132,000 kwh. That would be a difference of 66,000 kwh, or even at $0.10 / kwh of grid electricity end up being $6600 shift in favor of the li-ion. Of course, if you were recharging with solar cells off-grid you would have purchased the extra solar cells to offset this on a daily basis, but to generate about 9kw / day would take another 2kw (I'm guessing) or so of solar panels, which is still a noticeable cost.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Why not LiFePO4?

    Actually lead-acid batteries are more than 60% efficient. More like 80%. And you'll find the forklift batteries can do better than 1500 cycles. More like 7000.

    Curiously though this is a valid issue but for a somewhat different reason: generator charging. If you are in an area where gen charging is a fact of life then the ability to use the gen at high current most of the time becomes more fuel efficient, particularly over having to reach 100% SOC every so often which requires running the gen at its least efficient rate.

    So it would appear that the LiFePo has a greater advantage in the more questionable solar climates; places plagued by bouts of bad weather for example. There may also be an advantage with systems that run wind or hydro (the more constant charge input vs. fluctuating discharge).

    Still most of the problems reported with lead-acid are due to user mistakes and some companies that either build poor product or don't understand the application. To be fair there's no reason other battery chemistry can't suffer those same fates.
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Why not LiFePO4?

    Conservatively:

    81% panel derate * 95% charge controller * 80% Flooded Cell battery * 0.85 inverter eff = 52% end to end efficiency

    80-90% is a good range for Flooded Cell lead acid.
    90-98% for AGM

    That would take into account self discharge (old flooded cell fork lift batteries can be as much as 1-2% per day; AGM can be as little as a few percent per month).

    If you float/equalize the flooded cell a lot, run >80-100% state of charge, Lead Acid will be less efficient. Run them between 50-80% state of charge, lead acid will be more efficient.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Solar Expert Posts: 5,653 ✭✭✭✭✭
    Re: Why not LiFePO4?
    Maybe this is ridiculous, but I'm wondering if anybody ever took into consideration the recharging cost comparison between the li-ion and the PbA batteries. I'll let the experts correct the following theoretical situation if the assumptions are off, and probably the example is a bit extreme, but the figures have been previously presented as a point of debate. I also thought if the forklift batteries were cycled to 80% DOD they would be used up in about 1500 cycles, and the li-ion would be able to do maybe 3000 cycles at 80% DOD, so that is another variable that is in the equation but overlooked here.

    In the 680 usable ah @ 24V scenario, that would be about 16kwh / day that would need to be recharged. Over the 20 year lifetime of the batteries, that is 119,000 kwh that need to be recharged. If the PbA batteries end up 60% efficient (I think Bill says 50%, and Rolls has what seems to me 42%), that would mean you have to put in 198,000 kwh of recharge. I thought the li-ion was around 90% efficient, which would end up at 132,000 kwh. That would be a difference of 66,000 kwh, or even at $0.10 / kwh of grid electricity end up being $6600 shift in favor of the li-ion. Of course, if you were recharging with solar cells off-grid you would have purchased the extra solar cells to offset this on a daily basis, but to generate about 9kw / day would take another 2kw (I'm guessing) or so of solar panels, which is still a noticeable cost.

    You have the cycling correct, but the understanding IMHO wrong, it's not a direct comparison and can't be, they are used differently, but if you need(key word here) the capacity. You need the capacity. So even if you intend to live in the top 20% of charge, you may need the reserve. I don't want to run a generator, or make a generator a part of the equation.

    Lead acid batteries run around 85% efficient charging, I think your thinking total system loss, you will still have panels, wiring, inverter losses through out your system regardless of battery chemistry. One of the nice things is LifePO4 will take the same charge rate to nearly 100% capacity. Lead acid taper off at 85-90% and don't like to charge above 13-15% or rated capacity.

    Mostly they can't be directly compared, if you like to compare by cycles, you would have to have a system that used even cycles, typical systems don't work that way. LifePO4 works out better if you have alternate sources of power. since it can be reduced to a minimum usable capacity, before you connect the alternate energy source.

    My mistake on usable capacity, I meant 80% of 800Ah(at 24v)or 640Ah. If a LifePO4 battery would cost $10,000 for this reserve, I would be able to go through nearly 4 forklift/traction battery lives.

    FWIW mine weighs in at 1100lbs.
    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.
  • feedhornfeedhorn Solar Expert Posts: 103 ✭✭
    Re: Why not LiFePO4?

    Still most of the problems reported with lead-acid are due to user mistakes and some companies that either build poor product or don't understand the application.

    On my last set of golf cart batteries (Interstate) I made the mistake of assuming that the manufacturer would put in the correct SG of acid. They were at 1.310 when I got them new. I should have known better than to trust manufacturers and diluted the acid down to 1.265 immediately. My Bad. They sulphated quickly and were gone in two years.
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