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Lead Acid vs Lithium Iron Phosphate ( LFP; LiFePO4 )

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  • Lead Acid vs Lithium Iron Phosphate ( LFP; LiFePO4 )

    So, for the last week, I've actually been pretty interested in Lithium* batteries, and following several threads on several different boards.

    I've not purchased my battery bank yet, and am considering the Luthiums, something like the Thundersky EV batteries. Then I need 16 cell balancers, and a control box to shut down my charger.

    Looks like a 100A LFP has nearly the same usefullness as a 400A lead battery (can discharge deeper)

    Any ideas about recharge efficency - lead acid seems to be about 80-90% for flooded. What would LFP be?

    Any packaged "drop in" kits with BMS and modules to control 60A MPPT PV chargers?

    mike
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

  • #2
    Mike lithium charge efficiency is around 90% vs 80 % for LA.

    However there may be a flaw in your analogy on capacity. While it is true you can discharge lithium as much as 80% DOD without capacity degration and use a smaller AH capacity than LA chemistry, that may not be a good idea in a RE application. In a RE application you really want a minimum of 5 day capacity to carry you through cloudy days. Otherwise you are going to be forced to recharge with a generator or other conventional source. If you go in with Lithium based on 50% DOD per day, you are going to have to use a generator regularly. Based on that logic LA chemistry is a lot more economical because LFP is about 4 to 10 times the cost per watt hour.

    There are some other technical and economic considerations. One you mentioned is a BMS (battery management system). With lithium chemistry you will need a BMS to charge and monitor the system. Those are very complex and expensive custom designs well beyond any DIY and many electrical engineers capabilities.

    I would really like to see lithium become a default selection, but right now mostly due to economics, lithium will remain a very niche application where weight and size have a higher priority than economics.

    Lastly there could be some interface issues with user equipment such as inverters. Today's inverters and utilization equipment is made to work with lead acid chemistry voltage range. Lithium runs a bit higher and flatter which is a good thing in the long range, but not always compatible with equipment available. For example a typical 12 volt inverter is designed to operate from 14 volts down to 10.5. A lithium 4 cell 12 volt pack at full charge is 16 down to about 13. That may cause some incompatibility issues.
    MSEE, PE

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    • #3
      I'm looking at a 16 cell, 52V 160Ah LIP setup. That comes VERY CLOSE to a 48V lead acid bank. It would mostly be adapting stuff from EV's, but I'm not sure about the final touches for the battery management, and yes, daytime loads messing with the last 10% of charge.
      Nightly, I'm currently planning on only a fridge, freezer and some lighting, so 2-3 days before i hit 80% discharged. I'll likely run the genset before then.

      cost ways - it's about the same as a 200AH AGM bank - over $5K
      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

      solar: http://tinyurl.com/LMR-Solar
      gen: http://tinyurl.com/LMR-Lister

      Comment


      • #4
        Interesting Mike, more details please. The BMS is going to be your hurdle in terms of expense and modifications.

        Not trying to plug a web site but there is a very good forum for EV's whose membership has a lot of engineers from the EV field and BMS is a huge subject which I think you will find useful. FORUM HERE.
        MSEE, PE

        Comment


        • #5
          Originally posted by Mike90250 View Post
          cost ways - it's about the same as a 200AH AGM bank - over $5K
          Just caught this Mike. Why AGM over FLA? I thought I read when I first joined you were using L-16's
          MSEE, PE

          Comment


          • #6
            Originally posted by Sunking View Post
            Just caught this Mike. Why AGM over FLA? I thought I read when I first joined you were using L-16's
            Just priceing, still planning on the L-16s, but if I was getting AGM, at half the current capaicty as I've planned, the LFP starts to get compariable.
            Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
            || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
            || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

            solar: http://tinyurl.com/LMR-Solar
            gen: http://tinyurl.com/LMR-Lister

            Comment


            • #7
              LiFePO4 = Lifepower

              Although I am no expert on solar power - I have had some experience with these batteries - I have a couple of 48v 20ah jobs that I use for my electric bikes. A 15 cell pack would be closer to the lead acid 48v - These batteries (16 cell) run up to just over 60v and cut out just below 50v. There normal running voltage is around 54v and they run at this range for around 95 percent of the cycle. The first 10 cycles should be run down to 30 percent discharge and then you are good to go for 5000 plus cycles after which you only get 85-90 percent use. If you look on Ebay (48v 20ah battery) you can sometimes rangle (bid) one for around 450 - 500 dollars with BMS and charger - postage paid. You can run a regular SLA 48v (16 cell pack) to charge for the type of use you are looking at this may be safer as you do not want to exceed 60v. You can get some pretty cheap deep cycle batteries but they do not give the life cycle even if the discharge is a third. Best I have gotten with SLA's is approx. 300 cycles - I will probably be old and gray before my LiFePowers give out. Oh did I tell you about them being "almost" bullet proof - they will still run quite well after being shot at, or cut in half!

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              • #8
                See my posts on using LiFePO4 ...

                http://www.solarpaneltalk.com/showth...hlight=lifepo4

                I think it's an easy choice.

                Comment


                • #9
                  And the Price Drop

                  My brother purchased a 12v 60ah battery recently at http://elitepowersolutions.com/produ...products_id=96 with the BMS for under 400 dollars. These batteries are good for trailers to lighten the load and are less then half the weight. With a discharge to over 90 percent and capacity to run at twice the rated amp hour rating you cannot beat these. Of course they only last 2000 cycles if charged at over 40 amps but will last 5000 cycles if charged at 10 amps. Unlike a lead acid battery - these can sit at half a charge for days without damage to the battery.

                  Comment


                  • #10
                    BMS issue = not an issue

                    Every time somebody throws the BMS issue at other types of batteries, beside Lead Acid (LA) I basically tell them that the only difference is that LA batteries gas until they balance. Typically a BMS issue is different for a model plane operator then a solar storage system. In a model airplane you want to charge to the max for the longest flight (usually an extra minute) In a 48v LiFePO4 battery you BMS up to the 60v which only lasts for 3 percent of the batteries output duration at which point the battery drops to the running 54v which lasts for 94 percent. When you use a LA charger on this battery (LiFePO4) it never gets to the 60v BUT it has a different BMS which discharges the higher cells to match the LOWEST CELL. The only added features of some BMS's is the cutout before the power drops below 40v which most do with a relay since it is quite sudden within the last 3 percent. Note that these batteries are environmentally friendly = you take off the terminals and throw them in the dump. Also there are no explosive issues with overcharging - they gas just like LA - but do not have vents so they expand.

                    Comment


                    • #11
                      IF anyone is interested this is how I have set up 3 x100ahr LiFePo4 batteries for charging by solar and for use with MSW inverter..
                      Im not claiming this is the correct way or even the best way to do it,, But dont tell me it wont work as all 3 systems been in use over 2 years now with NO PROBLEMS
                      Charger a 30a PWP 12v charger set to output 14.8v with no equalization..
                      Battery cell over charging 1x 3.9V 1watt zenner diode and 1x10ohm resistor across each cell
                      One low voltage sensor set to disconnect the inverter and anything else connected to the battery pack at 10v
                      Facts as found out the expensive way by me are if you discharge a cell below about 2.2 v it will be destroyed even if done just one time only.
                      If you over charge above about 4.4v they have a very short life.
                      If you look at charts from the manufacturesr you find there is little power above 3.8v and it stays fairly constant until about 2.5v then hits a brick wall.
                      So use between those 2 voltages and all is well with the world.
                      I have never found a MSW inverter that has problems with operating between 15.5v and 10.5 v and that is the usual specs given by most MSW invereter manufacturers..

                      Comment


                      • #12
                        I think in the near future we will see LFP batteries entering the mainstream Renewable Energy market, but for now cost is still the big issue. I am aware of the cheap Chinese copy cat battery like Thundersky as I have a 48 volt stack in my Golf Cart - NEV. However they are cheap copies and will never last like A123 Systems 10,000 cycles. You may get 1000 cycles out of them with a good BMS. At 1000 cycles is not much better or any better than FLA currently on the market

                        The one big flaw of LFP as has been pointed out is just one small mistake or malfunction of the charging system can turn thousands of dollars of LFP batteries into a boat anchor, so a good high quality BMS with careful monitoring and oversight is a must have.

                        Fortunately the LFP market is being driven by the Electric Vehicle market, and RE applications will be a spin off some day soon IMO as A123 Systems now has pouch and prismatic systems out on the market with built in BMS, 10,000 cycles, and 140 wh/kg density. Just what the EV market needed. Problem is the $3 wh cost. A small 10 Kwh system will run you $30,000. This price has to come down to 15-cents per WH to go into the RE market.
                        MSEE, PE

                        Comment


                        • #13
                          Sunking wrote - Problem is the $3 wh cost. A small 10 Kwh system will run you $30,000. This price has to come down to 15-cents per WH to go into the RE market.

                          I do not know where you buy your batteries - but I have two 48v - 20ah (1kwh each) a123 systems with BMS and charger and I paid $350 (from China) for each and they have been running 5000 mi each on my electric bikes for two complete summers with six months layovers.

                          Sunking wrote - The one big flaw of LFP as has been pointed out is just one small mistake or malfunction of the charging system can turn thousands of dollars of LFP batteries into a boat anchor.

                          Your right - you cannot use a desulfate type LA charger on these batteries which is common in golf cart chargers.

                          Comment


                          • #14
                            how much for 10kWh?? - my 15kWh system was US$7000 ... with a BMS for solar. Yes it's Chinese and you may have stigma issues, but the *technology* even for poor quality puts my battery pack our at 1500 cycles for 80% DOD that's 12kWh in my case.

                            Granted for an electric car (fast charge and very fast discharge) the likelyhood of a cell imbalance is magnified and a *good* BMS is needed, but not for solar - and I would err on the side of A123 cells for an automotive app probably.

                            I pull 150A from my battery pack no problems (0.5C) and charging is at 60A (0.2C) ... so nice and gentle.

                            Comment


                            • #15
                              Originally posted by dave View Post
                              I do not know where you buy your batteries - but I have two 48v - 20ah (1kwh each) a123 systems with BMS and charger and I paid $350 (from China)
                              Want to try that again? A123 Systems are not a Chinese product and cannot be bought by a consumer. A123 System is strictly a USA company with manufacturing in USA only as of now Only OEM's can buy A123 System products. Only way for consumers to get them is buy battery packs in things like DeWalt power tools, and then scavenge them to be resold at very premium prices. A123 Systems Prismatic and Pouch series are only sold to automobile manufactures for Electric Vehicle use.

                              If you bought it from a China supplier they are not A123 Systems products, more likely a copy cat Thendersky product which is not any A123 System quality.
                              MSEE, PE

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