LiFePO4 - The future for off-grid battery banks?

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  • Reidec
    Junior Member
    • Feb 2012
    • 2

    #91
    Checking in. Lots of great info thanks all.

    I will admit that this one post was spam to get the picture viewing ability.

    Fairly new to solar. And I've had interest in LFP bats since I first started researching battery banks. I live in Oahu Hawaii and although we barely have any power problems or any reason to keep a battery bank, we pay $0.25-$0.33 a KwH. Now if you consider an LFP at around it's minimal charge cycle of 2000. Due to our high cost of KwH the batteries would be about the same cost as buying from the grid (given you're not coughing up huge amounts of cash for a bms). Further if I can extend the batteries life by keeping it within the 28% range, the batteries should be able to pay for themselves and then some.

    Of course the above is all hypothetical. Point being this post has been the most educational read compared to hopping around google hours upon hours. So I apologize if I spammed my first post but I wanted to see the PICTURES >.<.

    My current project I'm working on is a 12v 40Ah solar generator. Very tiny and really just something I'll probably take to picnics to run a small bose 30w sound system or my computer's companion system. I'm just having a ton of problems with the bms portion. I was looking at AU's Ev-power bms as a cheap option but T1's CellLogger 8 looks like a great alternative too. Having to maintain the batteries could be a great learning experience.

    If anyone has any other suggestions I'd be happy to hear them. But I assure you I have no intention of getting a high post count. Are you an admin?

    T1 Terry on the Junsi CellLogger 8, question is how often would I have to check on the log and adjust. I'm also assuming the adjustment would be made from the controller of course. And would you recommend a controller?
    Last edited by Reidec; 02-21-2012, 09:16 PM. Reason: I'm apparently flagged for spam...

    Comment

    • Sunking
      Solar Fanatic
      • Feb 2010
      • 23301

      #92
      Originally posted by Reidec
      Checking in. Lots of great info thanks all.
      Me thinks you are a SPAMMER. You are being watched, so time for you to get paranoid.
      MSEE, PE

      Comment

      • Mike90250
        Moderator
        • May 2009
        • 16020

        #93
        Well, you havent' mentioned what your charging source is. If you have a pickup truck, a "monolith" will fit into half the bed.

        My rig the Solar Monolith:

        Update pictures/information here.


        Check this thread too
        If you are a homeowner who is about to put a solar panel system on your home or you are a newbie to the solar market, get started here! A non-technical forum to help you understand the in's and out's of solar.
        Attached Files
        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

        • Reidec
          Junior Member
          • Feb 2012
          • 2

          #94
          I do have a pick up truck but prefer to avoid a heavy item. Even more the reason to stick with the LFP. Building my first panel in the next couple days it'll be a 18v 3.7AH poly panel. I'm thinking I'll end up using a 18v 6AH mono panel to actually charge this project though. Any recommendations on what to do with my little 60 watt panel? Should I avoid connecting the 2 panels in parallel due to the different materials? In all actuality I suppose I could use the 60 watt to keep the batteries topped and charged according to my math anyway.

          12*40 = 480w, 70% = 336w, 336w/30w = 11.2 hours.

          Chances are I won't even run it for more than 150w per night so a 60 watt panel shouldn't have any problems keeping it topped off.

          Also any recommendations for a 4 or 8 cell simple bms?
          Last edited by Reidec; 02-25-2012, 11:16 PM. Reason: forgot to ask a question

          Comment

          • microvast
            Junior Member
            • Mar 2012
            • 1

            #95
            Microvast -Lifepo4 manufacturer

            Microvast is US-ventured manufacturer of Lithium ion battery cell and battery pack. Our production base is in China,headquarter in Texas USA. With outstanding skill and experience, Microvast can offer kinds of power solutions for power tools, E-bike, E-scooter, E-motorcycle, Electric car (EV/HEV/PHEV), Energy storage syste.Our products main in Lifepo4, NCM and LTO battery.

            We produce cylindrical 18650 and 26650 Lifepo4 cells. By form cells into large module and pack with BMS, we have developed lot projects with our clients around world. Also we are the first large-scale industrial level LTO battery producer in the world. Our NCM 18650 cell is lowest iner impedance which can bear 15C discharge rate.

            please visite our website for more infomation:
            microvast.com


            Moderator note, if you wish to advertise, contact user JASON.
            Last edited by Mike90250; 03-07-2012, 02:38 AM. Reason: Free Commercial Ads not allowed. Moderator.

            Comment

            • TommyL
              Junior Member
              • Mar 2012
              • 18

              #96
              Originally posted by steveg
              The charge efficiency of LiFePO4 is very high and we live in the top 30-40% of the battery so I expect my lifetime of the cells to be high.
              Hello Steveg!

              Very clean install! Does anyone actually have "Charge Efficiency" comparison between LiFePO4 and AGM/Wet Cells?

              I'm testing Headway cells. A 32ah 12v pack can provide current to 2.5C (80amps) and give their full rating 24 minutes.
              The 12v/50ah rated AGM drawing 1.6C (80amps) only lasted 12 minutes.

              41lbs
              AGM 13.2v (no load)
              AGM 11.5v (80amp load applied)
              AGM 10.5v (at 12 minutes)


              10lbs (closer to 15lbs with busbars)
              LiFePO4 13.2v (no load)
              LiFePO4 12.6v (80amp load applied)
              LiFePO4 12.26v (at 20 minutes)
              LiFePO4 11.0v (at 26 minutes)

              AGM lasted 12 min vs LiFePO4 26 min
              The LiFePO4 was still at 12.29v at the 20min mark.
              I ran this test using 800watt resistant load (8 100watt light bulbs on light board)
              and a Xantrex 1000watt Inverter.

              What are you using for BMS?
              Again, Very nice clean install!

              Tommy L sends...

              If your Lead Acid bank is not large enough, there is no doubt that voltage sag occurs.

              Comment

              • Mike90250
                Moderator
                • May 2009
                • 16020

                #97
                What are you using for BMS?
                Agreed - the BMS for Li based batteries, is a problem. That usually leaves users to either cobble together something of their own, or risk battery damage by going without a BMS.
                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

                • steveg
                  Member
                  • Oct 2010
                  • 42

                  #98
                  Originally posted by TommyL
                  Hello Steveg!

                  Very clean install! Does anyone actually have "Charge Efficiency" comparison between LiFePO4 and AGM/Wet Cells?

                  I'm testing Headway cells. A 32ah 12v pack can provide current to 2.5C (80amps) and give their full rating 24 minutes.
                  The 12v/50ah rated AGM drawing 1.6C (80amps) only lasted 12 minutes.

                  41lbs
                  AGM 13.2v (no load)
                  AGM 11.5v (80amp load applied)
                  AGM 10.5v (at 12 minutes)


                  10lbs (closer to 15lbs with busbars)
                  LiFePO4 13.2v (no load)
                  LiFePO4 12.6v (80amp load applied)
                  LiFePO4 12.26v (at 20 minutes)
                  LiFePO4 11.0v (at 26 minutes)

                  AGM lasted 12 min vs LiFePO4 26 min
                  The LiFePO4 was still at 12.29v at the 20min mark.
                  I ran this test using 800watt resistant load (8 100watt light bulbs on light board)
                  and a Xantrex 1000watt Inverter.

                  What are you using for BMS?
                  Again, Very nice clean install!

                  Tommy L sends...

                  If your Lead Acid bank is not large enough, there is no doubt that voltage sag occurs.
                  A quick google search gave me :

                  Charge Efficiency PbA

                  12V SLA battery charger,lead acid battery charging techniques and algorithms,sealed lead acid batteries,Pb battery,SLA,VRLA,Gel,Flooded and AGM batteries.


                  For LiFePO4 see figure 5

                  Comment

                  • TommyL
                    Junior Member
                    • Mar 2012
                    • 18

                    #99
                    Originally posted by steveg
                    A quick google search gave me :

                    Charge Efficiency PbA

                    12V SLA battery charger,lead acid battery charging techniques and algorithms,sealed lead acid batteries,Pb battery,SLA,VRLA,Gel,Flooded and AGM batteries.


                    For LiFePO4 see figure 5
                    http://www.batterypoweronline.com/eprints/TI_0510.html
                    Thank you for the links..... but my question was....

                    What are you using for BMS?
                    Do you have a build thread?

                    Tommy L sends....

                    Comment

                    • john p
                      Solar Fanatic
                      • Oct 2010
                      • 738

                      Tommy l if you use the 10ahr cylinder cells its very simple to make a BMS for them unfortunately its not as easy to upscale to the much larger(100to 200ahr)cells

                      Comment

                      • steveg
                        Member
                        • Oct 2010
                        • 42

                        Originally posted by TommyL
                        Thank you for the links..... but my question was....

                        What are you using for BMS?
                        Do you have a build thread?

                        Tommy L sends....
                        Hi,

                        You question was asking about charge efficiency too

                        My pack came with a BMS - and as mentioned above you should use larger format cells - say 100Ah 3 in parallel * 16 in series - or 300Ah cells 16 series, generally there isnt too much price penalty either way.

                        I am currently designing a flyback charge balancing BMS for cell and supercap I was hoping to sell - it's 3 to 5A and doesnt bleed power through resistors, hopefully superior, with full reporting via RS485/232 - a while away for now though as I have other projects nagging.



                        Regards,

                        Steve.

                        Comment

                        • TommyL
                          Junior Member
                          • Mar 2012
                          • 18

                          Originally posted by steveg
                          Hi,

                          You question was asking about charge efficiency too

                          My pack came with a BMS - and as mentioned above you should use larger format cells - say 100Ah 3 in parallel * 16 in series - or 300Ah cells 16 series, generally there isnt too much price penalty either way.

                          I am currently designing a flyback charge balancing BMS for cell and supercap I was hoping to sell - it's 3 to 5A and doesnt bleed power through resistors, hopefully superior, with full reporting via RS485/232 - a while away for now though as I have other projects nagging.



                          Regards,

                          Steve.
                          I stand corrected!
                          Super capacitors are very interesting. I look forward to the day that you test your new device.
                          Lots of Experimenting/Observing and taking notes continuing in my future.

                          I appreciate your input!
                          Take care...

                          Tommy L sends....

                          Comment

                          • TommyL
                            Junior Member
                            • Mar 2012
                            • 18

                            Originally posted by john p
                            Tommy l if you use the 10ahr cylinder cells its very simple to make a BMS for them unfortunately its not as easy to upscale to the much larger(100to 200ahr)cells
                            What do you have up your sleeve for the 10ahr cylinder cells?

                            Although they are not the cheapest of the LiFePO4 storage per w/h, I do like the
                            the ease of switching out a problem cell without loosing too much money

                            Tommy L sends.....

                            Comment

                            • john p
                              Solar Fanatic
                              • Oct 2010
                              • 738

                              TOMMYL read my post #26 it explains it .I hope, thats the big advantage if you using a lot of cells if one becomes faulty very easy to just replace that cell only,keeps costs of replacements los as you are not throwing away good cells also.

                              Comment

                              • TommyL
                                Junior Member
                                • Mar 2012
                                • 18

                                Originally posted by john p
                                TOMMYL read my post #26 it explains it .I hope, thats the big advantage if you using a lot of cells if one becomes faulty very easy to just replace that cell only,keeps costs of replacements los as you are not throwing away good cells also.
                                Totally agree! Not for the "Set and forget" style people. I've been building, fixing, making, designing, prototyping all my life. I enjoy
                                being involved and tweaking my work.

                                I look forward to readying your post/threads! I appreciate your input!
                                I have around 100 38120HP (Red) Headway cells. I've been testing them. Low resistance cell.

                                My plan is to bring in 1,000 or more pcs for commerce.

                                Tommy L sends...

                                Comment

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