Announcement

Collapse
No announcement yet.

LFP battery chatter ( AKA LiFePo4, Lithium Iron Phosphate )

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • LFP is no ready for solar. I still do not recommend it for Joe Homeowner. Still way too may questions and complete lack of equipment to support LFP on solar. Most of it related to economics and market demand.

    LFP like lithium chemistry is still unproven and has failed to live up cycle life claims. Pretty hard to convince someone to make that kind of investment for unknown results. Secondly as anyone who has gone down the LFP road has discovered there is no fool proof or compatible equipment. To pull it off requires a significant bit of knowledge.
    MSEE, PE

    Comment


    • Originally posted by Sunking View Post
      LFP is no ready for solar. I still do not recommend it for Joe Homeowner. Still way too may questions and complete lack of equipment to support LFP on solar. Most of it related to economics and market demand.

      LFP like lithium chemistry is still unproven and has failed to live up cycle life claims. Pretty hard to convince someone to make that kind of investment for unknown results. Secondly as anyone who has gone down the LFP road has discovered there is no fool proof or compatible equipment. To pull it off requires a significant bit of knowledge.
      Dereck, as someone who pretty much decided to go with LFP based on the discussion here, I am wondering if you could you explain your view with a few more specifics? (So I know if I need to switch course)

      What I am hearing in this short summary statement is:
      1. Not ready for Joe Homeowner (which I understand)
      2. Complete lack of equipment (which I assume principally refers to integrated shunting and industry wide adoption of LVD and HVD)
      3. failed to live up to life cycle claims.

      I am curious about anything further you say about 2. and 3. This is the first I have heard about failure to live up to lifecycle claims. Could I readily find out more by doing a Google search, or can you give specific examples? In regards to "complete lack of equipment," is there more functionality needed than integrating BMS functions? It seems this criticism is the cause of 1. - That LFP is not ready for solar (or perhaps solar is not ready for LFP).

      Comment


      • Originally posted by Living Large View Post
        Dereck, as someone who pretty much decided to go with LFP based on the discussion here, I am wondering if you could you explain your view with a few more specifics? (So I know if I need to switch course)

        What I am hearing in this short summary statement is:
        1. Not ready for Joe Homeowner (which I understand)
        2. Complete lack of equipment (which I assume principally refers to integrated shunting and industry wide adoption of LVD and HVD)
        3. failed to live up to life cycle claims.

        I am curious about anything further you say about 2. and 3. This is the first I have heard about failure to live up to lifecycle claims. Could I readily find out more by doing a Google search, or can you give specific examples? In regards to "complete lack of equipment," is there more functionality needed than integrating BMS functions? It seems this criticism is the cause of 1. - That LFP is not ready for solar (or perhaps solar is not ready for LFP).
        We are kind of beating a dead horse, but to recap.

        2. We have discussed this in great length. Current solar CC have no communications port to work with any BMS, LVD, HVD. You can work around it if you know what you are doing. Joe Homeowner does not know what he/she is doing. Thus only well informed people should even attempt it.

        3. To date no lithium battery have lived up to its claimed cycle life. What joe Homeowner is looking at is Chi-Com LFP because like CALB, Winston, Sinopoly ect are all from failed bankrupt Chi-Com companies. A lot of that has to do with too dang many manufactures and not a large enough market to keep that many in biz. All of the designs out now are new and have not stand the test of time. I am not saying they will not perform, but it is unknown and one is taking a chance, myself included because I own a set for my golf cart.

        Bottom line is EV's are the driving force, and battery technology will come from that development. It is still in its infancy baby stages. Solar and RE will just be a side benefit. Which lithium chemistry will win is unknown and unlikely discovered as of yet.

        Having said all that, I do feel good and have taken the dive using GBS in my golf cart. Only been a few months but so far so good without any performance issues so far. With Pb and the amount of use I have put on the LFP would have just formed the plates and maximum performance. I have no capacity loss or Ri issues as of yet. Looking good so far. One thing that helps that does not apply to the USA is I do not have cold weather and lithium is significantly effected by cold temps. Mind you cold does not damage the battery, exact opposite, but it does impact capacity and Ri significantly.
        MSEE, PE

        Comment


        • Dereck,
          It would help if you clarify the meaning of "have not lived up to life cycle claims"
          That could mean either:
          1. They have not yet had time to be tested to that many cycles in actual PV/RE use, or
          2. When used for RE they have have failed sooner than the life cycle graphs predicted.
          Thanks!
          SunnyBoy 3000 US, 18 BP Solar 175B panels.

          Comment


          • Originally posted by Sunking View Post
            We are kind of beating a dead horse, but to recap.{snip}
            Agreed, but I wanted to make sure I didn't miss something. Thank you for your further thoughts.

            Joe Homeowner needs something he doesn't need to think about. Like getting in a car and driving. Using LFP today I suppose presents challenges something like driving a vintage 1908 car on a vintage 1908 road.

            Comment


            • When properly designed, fabricated and installed by a competent engineer/solar technician, an LFP system requires about zero maintenance and attention other than monitoring system to determine the power management cycle one will utilize in the next several days. That is, will there be a lot of solar insolation or will it be overcast. This is the manner in which I choose to live.

              Sunking and Cariboucoot (from Northern Arizona) are justifiably worried about DIY'ers getting in over the head in projects. However, a lot of Aussies have done LFP systems with mutual support and information exchange as is evidenced on the two Aussie fora: Grey Nomads and Caravansforum.com. These systems are usually 4 cell (12 V nominal) and do not require BMS but just top/bottom balancing (an arduous task apparently) and then setting cell voltage to maximum of 3.4 V.

              I scarcely am about to buy a collection of electronic parts and try to assemble a digital camera, Iphone, or any other modern electronic device by myself. The days of building your own computer from Tandy kits aka the famous and beloved "Trash 80" (Tandy/Radio Shack, Z-80 microprocessor") which our older son assembled around 1980 and upgraded to 16 kB, are long gone.

              Reed Cundiff

              Comment


              • Originally posted by reed cundiff View Post
                I scarcely am about to buy a collection of electronic parts and try to assemble a digital camera, Iphone, or any other modern electronic device by myself. The days of building your own computer from Tandy kits aka the famous and beloved "Trash 80" (Tandy/Radio Shack, Z-80 microprocessor") which our older son assembled around 1980 and upgraded to 16 kB, are long gone.

                When properly designed, fabricated and installed by a competent engineer/solar technician, an LFP system requires about zero maintenance and attention other than monitoring system to determine the power management cycle one will utilize in the next several days. That is, will there be a lot of solar insolation or will it be overcast. This is the manner in which I choose to live. A lot of Aussies have done LFP systems with mutual support and information.

                Sunking and Cariboucoot may consider discussion on LFP is beating dead horses but their considerations do not seem to bear much resemblance to what everyone I know of that utilizes LFP in RV's that consider it on their on-line blogs: Wheeling it, Gone with the Wynnes, Ron Jones, and a dozen others I know of from correspondence. The Aussie RV fora have several dozen users that are delighted.
                Reed Cundiff
                I understand your response, and I greatly value what Dereck, you and everyone has put forth in this thread (back when the horse was still at full strength). Going in with eyes wide open, understanding the risks, and being able to tell when and if things are going wrong - these are all things important to me. One mistake with LFP, and I could vaporize $10,000 of batteries. I need to accept and manage that risk, and understand how to avoid that condition for LFP to be an option. And it takes a custom solution, since the electronic management is currently not built into off the shelf equipment. In this sense, I understand the "not ready for Joe Consumer" view. Imagine a furnace, an air conditioner, etc that requires babysitting and strap-ons to keep it from self destructing.

                Comment


                • When properly designed, fabricated and installed by a competent engineer/solar technician, an LFP system requires about zero maintenance and attention other than monitoring system to determine the power management cycle one will utilize in the next several days.
                  Yep, until the day it goes dark and the user doesn't have a clue why his investment has headed south.

                  Comment


                  • On the surface I agree with most of what is written, but I feel that there is a LOT of money to be made by overcomplicating the whole issue.

                    I'm the lone wolf here and refuse to overcomplicate. Under normal use in my own "Sub-C" application, it needs to be as simple as lead acid to operate. So far, so good.

                    Is it really that hard to do this:

                    * Do an initial balance to make sure the cells are even or relatively close in capacity. If one was running individual 2v lead acid cells, they would do the same right?
                    * Don't overcharge beyond 3.6v
                    * Don't over-discharge. Employ an LVD of some sort be it your brain or a physical LVD.
                    * Stay out of the steep charge-discharge knees. Ie, run to 3.5v per cell and call it a day. Don't go under 3v, and certainly no lower than 2.5v.
                    * Don't undersize your battery tempting you to go to extremes. Stay a bit on the conservative side - solves a LOT of problems.

                    * Most importantly, recognize that these are just batteries with different characteristics, but like all batteries cannot magically operate without *some* care and diligence. And yes, stuff happens sometimes.

                    And unless one is a manufacturer or salesman, who CARES what your neighbors think about the chemistry you decide to run? Most are still confused about the difference between flooded/agm, SLI vs Deep Cycle lead-acid at this point anyway. Choose the battery with characteristics that float your boat.

                    I think as a group, we tend to try and put on the CTO hat for an imaginary company of our own, forever discussing business tactics, marketing and sales. Yawn. I have a day job.

                    Comment


                    • Originally posted by inetdog View Post
                      Dereck,
                      It would help if you clarify the meaning of "have not lived up to life cycle claims"
                      That could mean either:
                      1. They have not yet had time to be tested to that many cycles in actual PV/RE use, or
                      2. When used for RE they have have failed sooner than the life cycle graphs predicted.
                      Thanks!
                      #2 applies.
                      MSEE, PE

                      Comment


                      • Originally posted by Sunking View Post
                        To pull it off requires a significant bit of knowledge.
                        Shhh. Don't tell anyone this secret - 12v large prismatic users only - higher voltages do your own thing possibly.

                        * Immediately de-rate the advertised capacity to 80% of sticker value.

                        * Don't go bananas over TOP balance <0.10 volts, as voltage says nothing about the capacity or internal resistance. Each cell only has to be *reasonably* close to each other and each has it's own characteristics. Do a "sanity charge" to get within reasonable voltage balance first off. Use individual cell charger, balance charger, or other means for first charge.

                        * Be somewhat conservative. Allow no cell to go over 3.5v at the top, nor under 3.2v at the bottom. LVC at 2.5v or higher for dead-man catch. Use an HVC if you don't trust your controller / charger. Small variances allowed because again voltage is not the main story here. If your battery is sane to start with, pack-level monitoring and charging works by being conservative and the fact that we typically doing 0.1C, not 1C and higher like EV'ers do. We have time on our side.

                        * Rely on coulomb-counting (counting amphours) and don't try to exceed 80%, although near the bottom, when you reach 12.8v overall, you are mostly done if you aren't counting coulombs.

                        * Works for me. At 12v so far. YMMV. <------ standard disclaimer

                        Comment


                        • Originally posted by PNjunction View Post
                          * Rely on coulomb-counting (counting amphours) and don't try to exceed 80%, although near the bottom, when you reach 12.8v overall, you are mostly done if you aren't counting coulombs.
                          I agree with Coulomb Counting, just not the amp hour part. Amp hours go in at higher voltages than they do coming out. Something the EV crowd discovered real quick. Think Watt Hours.
                          MSEE, PE

                          Comment


                          • Originally posted by Sunking View Post
                            I agree with Coulomb Counting, just not the amp hour part. Amp hours go in at higher voltages than they do coming out. Something the EV crowd discovered real quick. Think Watt Hours.
                            +1
                            For battery SOC, think amp hours and coulombic efficiency. The voltage does not matter.
                            For cyclic energy efficiency you do have to think of watt hours instead. And you will lose watt hours both from voltage sag and from Peukert effect during discharge.
                            SunnyBoy 3000 US, 18 BP Solar 175B panels.

                            Comment


                            • Originally posted by inetdog View Post
                              +1
                              For battery SOC, think amp hours and coulombic efficiency. The voltage does not matter.
                              For cyclic energy efficiency you do have to think of watt hours instead. And you will lose watt hours both from voltage sag and from Peukert effect during discharge.
                              One good thing about Lithium is charge efficiency is so high, and Peukert effect so low at rates less than 1C can be ignored. With an EV you do have to account for efficiency and Peukert, but even then we are talking about over 95% round trip efficiency and all 5% is caused by Ri and wiring losses. With solar application C-Rates are normally well below 1C.

                              Additionally lithium has one operating characteristic no other battery I know of has. Ri is reverse coefficient meaning a lithium battery Ri is highest at 100% SOC and lower at 10% SOC. They actually have higher discharge efficiency as the SOC goes lower. All other batteries are the exact opposite.

                              One of the benefits of using LFP on a solar system is you can use slightly lower panel wattage which translate to lower initial installation cost. Unfortunately at this time is not saying much. That will change when and iff lithium battery prices come down, and a proven track record of cycle life.
                              MSEE, PE

                              Comment

                              Working...
                              X