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LifePO4 Cells

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  • LifePO4 Cells

    Hello Group,

    Today I am posting about a LifePO4 pack I have constructed and am testing. I share this stuff for the benifet of the group so that you can see what is out there and at least how one guy (myself) puts it together, along with some supplemental testing.

    This pack is constructed of Tenergy 5.5AH LifePO4 cells. Here is a picture of a single cell:

    https://1drv.ms/i/s!AmzmftzD-V0mhwo1TMrbdiz1bvNd

    The pack is constructed with a total of 40 cells. I made four banks of ten cells and put them in series. Here is a shot of the four strings assembled. I used welding rod for the bus bars, same kind as we use for coil cores. The plugs you see at the top are going across each cell pos and neg so that I can attach balancing boards which will be removable. I plan to build more of these packs and you only need the balance board while charging so I have made them detachable.

    https://1drv.ms/i/s!AmzmftzD-V0mhwsXG_6xcHaztEIQ

    The next step I took was to hot glue some foam sheeting to the pack. This is to minimize any accidental knocking around of the pack and protect the buss bars a little.

    https://1drv.ms/i/s!AmzmftzD-V0mhwyenX43bEoKVcS_

    To finish off the pack I wrapped it with hot tape. Here you can see the finished pack with the balance boards attached.

    https://1drv.ms/i/s!AmzmftzD-V0mhw3d9JK7lqqIhFWX

    https://1drv.ms/i/s!AmzmftzD-V0mhw7XC5WdF1r-YlpZ

    And just to see how it would go I hooked up my 400 watt inverter to the pack and charged another prismatic 20AH pack that I have. The charger is a 10 amp charger and everything ran fine, no heat on the batteries and the inverter and charger got slightly warm.

    https://1drv.ms/i/s!AmzmftzD-V0mhw-2-yig-OkRra1u

    Finally here is a discharge curve from CBA testing. This was a 10A draw and I got 50AH from the pack. Technically it should be a 55AH pack but I'm impressed with how well it performed. Most real life loads are not going to be a constant current and probably not 10A but it shows that this thing does store some serious power.

    https://1drv.ms/i/s!AmzmftzD-V0mhxAmNNnC8mYI4bKC
    Last edited by BobZilla; 01-22-2017, 10:50 AM.

  • #2
    Bob,

    wow!! that is impressive!!! will be very interesting to see how this setup serves your needs.

    Tom C


    experimental Kits, chargers and solar trackers

    Comment


    • #3
      Originally posted by BobZilla View Post
      Hello Group,

      Today I am posting about a LifePO4 pack I have constructed and am testing. I share this stuff for the benifet of the group so that you can see what is out there and at least how one guy (myself) puts it together, along with some supplemental testing.

      This pack is constructed of Tenergy 5.5AH LifePO4 cells. Here is a picture of a single cell:

      https://1drv.ms/i/s!AmzmftzD-V0mhwo1TMrbdiz1bvNd

      The pack is constructed with a total of 40 cells. I made four banks of ten cells and put them in series. Here is a shot of the four strings assembled. I used welding rod for the bus bars, same kind as we use for coil cores. The plugs you see at the top are going across each cell pos and neg so that I can attach balancing boards which will be removable. I plan to build more of these packs and you only need the balance board while charging so I have made them detachable.

      https://1drv.ms/i/s!AmzmftzD-V0mhwsXG_6xcHaztEIQ

      The next step I took was to hot glue some foam sheeting to the pack. This is to minimize any accidental knocking around of the pack and protect the buss bars a little.

      https://1drv.ms/i/s!AmzmftzD-V0mhwyenX43bEoKVcS_

      To finish off the pack I wrapped it with hot tape. Here you can see the finished pack with the balance boards attached.

      https://1drv.ms/i/s!AmzmftzD-V0mhw3d9JK7lqqIhFWX

      https://1drv.ms/i/s!AmzmftzD-V0mhw7XC5WdF1r-YlpZ

      And just to see how it would go I hooked up my 400 watt inverter to the pack and charged another prismatic 20AH pack that I have. The charger is a 10 amp charger and everything ran fine, no heat on the batteries and the inverter and charger got slightly warm.

      https://1drv.ms/i/s!AmzmftzD-V0mhw-2-yig-OkRra1u

      Finally here is a discharge curve from CBA testing. This was a 10A draw and I got 50AH from the pack. Technically it should be a 55AH pack but I'm impressed with how well it performed. Most real life loads are not going to be a constant current and probably not 10A but it shows that this thing does store some serious power.

      https://1drv.ms/i/s!AmzmftzD-V0mhxAmNNnC8mYI4bKC
      Hi Bob,

      Definitely a Combination of LFP and Lead acid in a SSG is the way ahead..
      Rgds,
      Faraday88.
      'Wisdom comes from living out of the knowledge.'

      Comment


      • #4
        Originally posted by Tom C View Post
        Bob,

        wow!! that is impressive!!! will be very interesting to see how this setup serves your needs.

        Tom C
        Thanks Tom. You know one thing I really want to try with one of these,,,, there is a place on a lake in my area where they rent john boats out for fishing. I want to take one of these packs there and see how it does with a trolling motor. One thing is certain, as DC supply it can put out an insane amount of current for it's size. That's just the way the lifepo4's are, another thing I want to try is to see if it could run my electric smoker but I doubt this pack is big enough to do a full cook. It could handle the load current fine but storage size I don't think it would last. I may try it when the weather is nice enough.
        Last edited by BobZilla; 01-23-2017, 09:32 PM.

        Comment


        • #5
          Hello Group,

          Today I am showing this LifePO4 pack being used in bedini tech. Faraday didn't elaborate much with his statement but I think what he was trying to say is the same as I will say here now. Lithium batteries make awesome primaries for many reasons. One of the biggest reasons is that you get almost no voltage drop across a run. You can see this in the chart below. This run was approximately 28 hours at 1A and the primary hardly sagged at all.

          The run was done on a SSR solid state mode one type of circuit. On the front we have the battery that this thread is about and on the back we had two garden batteries in series. These garden batteries were very depleted although you would not know it looking at their starting voltage. These batteries always bounce back up to a fairly high voltage no matter where I drag them down too, I think in part because of the radient charging they have received. I did not mention it in the video but I had actually run these down to about 9v by accident the night before with them as a primary in parallel. They had bounced back to around 12.2 from that and that is where they got setup for this charge.

          Anyway here are the charts:

          smallSSR_24v_charge.JPG

          smallSSR_24v_primary.JPG

          And a short video of the beginning and end of the run.

          link:
          https://1drv.ms/v/s!AmzmftzD-V0mhxURNumCu8x5iXIK

          Comment


          • #6
            that is a great run bob! I love the lithiums for primaries!! I use the LiFePo4 with a cap on the front on some of my runs, they seem to like it there, and the cap buffers the spike nicely.

            Tom C


            experimental Kits, chargers and solar trackers

            Comment


            • #7
              Originally posted by Tom C View Post
              that is a great run bob! I love the lithiums for primaries!! I use the LiFePo4 with a cap on the front on some of my runs, they seem to like it there, and the cap buffers the spike nicely.

              Tom C
              Thanks Tom. Yes I know what you mean with the cap, I have done that too. Originally I had this board setup with a very small cap on front and back and another SSR to control a dump for the output (notice the blank space on the board opposite of the 1st SSR), but I decided to go pure mode one with it for now. I change things around on my setups pretty often and am never really married to one setup for too long. This little board would make a fantastic portable unit though. I am thinking about getting a small solar panel, maybe 20 watt just for this unit to operate on. To me that is the huge advantage of going solid state, the sun can come out or hide and it will just go with it, no problem with a wheel stalling.

              I am going to try and put this run through a few cycles and add to this thread. I kept the charge chart running and hooked up the CBA this morning to pull them down again. I am going to try to keep it all charting and pop another run on it. Don't know if I will be able to get it, something usually craps out with the meter or the computer over such long continuous attempts but if I can get it I will post back. I'm sure the next run on them will go faster because this time they will be cut off at 21v.

              Comment


              • #8
                Nice work Bob!

                John K.

                Comment


                • #9
                  Thanks John.

                  Hey I know you are working on similar builds with the 18650's, if you have the funds you might consider getting some of these and testing them out for yourself too. I have both cheap 18650's and some actual name brands (efest) which live up to their rating but since I got these lifePO4 cells I cannot see investing any more in the 18650's, these are just SO much better. Anyway I know you are on your own path and I respect that but I'm just saying these cells are winners for sure.

                  @ Group

                  Guys the computer rebooted half way through the continuation of that run so I lost the charts. I thought it might happen but I am just following up because I said I might post more.

                  Comment


                  • #10
                    Thanks Bob,
                    Its great to have a guiding light through the new tech that is becoming available.

                    Comment


                    • #11
                      Originally posted by BobZilla View Post
                      Thanks John.

                      Hey I know you are working on similar builds with the 18650's, if you have the funds you might consider getting some of these and testing them out for yourself too. I have both cheap 18650's and some actual name brands (efest) which live up to their rating but since I got these lifePO4 cells I cannot see investing any more in the 18650's, these are just SO much better. Anyway I know you are on your own path and I respect that but I'm just saying these cells are winners for sure.
                      That's good news Bob. Will definitely look to get some LiFePO4's when I get some cash together.

                      John K.

                      Comment


                      • #12
                        I found this nice little study a guy did on charge voltages for lifePO4 cells and thought it worth pointing out here.

                        Link:
                        http://www.powerstream.com/lithium-p...ge-voltage.htm

                        I have been studying a bit on my own about this chemistry and how to work with it. The number one NO-NO is to go to a higher voltage. They love current but voltage above 4+ per cell will damage them. It has to do with the anode forming dendrites and causing shorts. There is a lot of conflicting information on this topic but if you read enough you start to get the picture, basically heat and voltages above 4 (per cell) cause failure.

                        Here is another paper to gleen from:
                        http://ecst.ecsdl.org/content/41/39/1.full.pdf

                        I know it has been said that charging with bedini tech will destroy lifepo4 chemistry but I wonder if it was the voltage that has done it? Mr. Bedini said not to do it and Tom has said it too but I wonder if we could make a limiting circuit to keep from crossing that over voltage zone.

                        I normally charge my lifepo4 packs with a charger that is made for them but supply that from my larger LA batteries that soak up the sun ( with an inverter). It works great but it is really inefficient this way. I am thinking about experimenting with setting a cap-dump to ramp up to 14v and dump, never going higher than the safe voltage zone for a 4S configuration. It seems to me that the pulse of the cap is not a problem and if the voltage is controlled it shouldn't hurt cells.

                        Has anyone played with this type of arrangement for lifepo4? I have a 20AH prismatic 4S pack that I have had for a few years now that I may subject to this treatment in the name of science ;-)

                        Comment


                        • #13
                          My understanding of what John Bedini and Tom have said it's not the tech so much as the uncontrolled tech, either charging too high or with too high of a voltage spike, that can damage a battery or possibly start a fire. I do not have any lithium batteries or I would probably try it too. (well that and I had a fire in my greenhouse and will be dealing with that mess for a while) My biggest caution would be sure you were present during the charging, such as don't leave them charging overnight. It would be nice if Tom could chime in here but he might not be able to, do to liability with his charger business.

                          Comment


                          • #14
                            Hi Bob, I think the cap dumper is a good idea and a neat way to limit the voltage so you don't damage the cells. I'd expect the dump rate to increase as the cell voltage increases, but the current pulses to decrease at the same time.

                            Another thought that comes to mind is a Bedini SG into a Bedini Linear Regulator Amp, however you may need to fiddle with the upper voltage limiter to dial it into your terminating voltage.

                            John K.

                            Comment


                            • #15
                              Originally posted by John_Koorn View Post
                              - snip -

                              Another thought that comes to mind is a Bedini SG into a Bedini Linear Regulator Amp, however you may need to fiddle with the upper voltage limiter to dial it into your terminating voltage.

                              John K.
                              Yup, this was the whole reason John B. came up with the Linear Current Amplifier...


                              I've found the LifeP04's love to feed on solar panels also...

                              - Patrick A.

                              Comment

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