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Thread: LiFePO4 Batteries - Lithium Iron Phosphate

  1. #1
    Networking Architect Aaron Murakami's Avatar
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    Thumbs up LiFePO4 Batteries - Lithium Iron Phosphate

    Here is some info about the LiFePO4 batteries. 5 time the life cycle of lead acids and way safer than typical "Lithium Ion" batteries (cobalt), which are toxic and flammable.

    They can be used with the Bedini SG technology or even Bedini's chargers. These batteries are constant voltage until they drop off the cliff so you get full capacity for nearly the entire time.

    Lead acids need to be pushed to 15.0 to 15.2 to be truly charged and fully desulfated - these LiFePO4 batteries only need to be pushed to 14.8 to be fully charged.

    At the end of this article, there is a link where you can see a video by Peter talking about these batteries and there is a link under that video where you can download a free powerpoint presentation on these batteries.

    http://emediapress.com/2014/09/09/li...ate-batteries/
    Aaron Murakami





    You never change things by fighting the existing reality. To change something, build a new model that makes the existing model obsolete. ― Richard Buckminster Fuller

  2. #2
    Hi Aaron,

    Thanks for the info, I was curious about these batteries. I have noticed that most spec sheets recommend pretty high current rates for charging so I am wondering if you have had experience charging them with SG mode one devices such as a monopole wheel?

    Of course normal lead acid batteries also recommend high current for charging and we all know it can be done on very little so I am wondering how these might compare to lead acid when on a wheel. In other words if a wheel can charge a LA garden battery fine would it be expected that it could charge a similar sized LifePO4?

    Thanks for the info and all the work you do for the community.

  3. #3
    Networking Architect Aaron Murakami's Avatar
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    Quote Originally Posted by BobZilla View Post
    Hi Aaron,

    Thanks for the info, I was curious about these batteries. I have noticed that most spec sheets recommend pretty high current rates for charging so I am wondering if you have had experience charging them with SG mode one devices such as a monopole wheel?

    Of course normal lead acid batteries also recommend high current for charging and we all know it can be done on very little so I am wondering how these might compare to lead acid when on a wheel. In other words if a wheel can charge a LA garden battery fine would it be expected that it could charge a similar sized LifePO4?

    Thanks for the info and all the work you do for the community.
    Hi, thank you Bob.

    Paul Babcock has a 24v SG at his shop and was charging a 24v lifepo4 bank of maybe 10-20ah size with the spikes and it worked better than expected and he was able to swap batteries back to front, etc...

    I believe John said they like the current so may charge better with the linear current regulator output circuits, which is the same principle as the solar charge controllers he built for these.

    So between both of those statements, I'm not really sure what is the best but they both evidently work. Because of the high cost, I'd be more cautious and would probably stick with a steady current charge instead of the spikes until we know better over time but I'm very interested in comparing the results.

    One interesting thing to note is that the LiFePO4 batteries have ions that are WAY less massive than the lead ions so are put into charge mode more easily so this tells me that current is not the only answer. With spikes we can charge the lead acids incredibly well and with the lithium iron phosphate batteries, you can practically blow on them and they start charging. Now is the heavier lead ions an advantage because they can sustain their momentum longer? I don't know but I think these are the questions we need to ask for these applications.

    Here is a wiki reference to the lifepo4 ions being put in to charging mode...

    "Its key barrier to commercialization was intrinsically low electrical conductivity. This problem was overcome by reducing the particle size, coating the LiFePO
    4
    particles with conductive materials such as carbon, and doping[4] the result with cations of materials such as aluminium, niobium, and zirconium. This approach was developed by Yet-Ming Chiang and his coworkers at MIT.[citation needed] Products are now in mass production and are used in industrial products by major corporations including Black and Decker's DeWalt brand, the Fisker Karma, Daimler, Cessna and BAE Systems.[citation needed]

    MIT has introduced a new coating that allows the ions to move more easily within the battery. The "Beltway Battery" utilizes a bypass system that allows the lithium-ions to enter and leave the battery at a speed great enough to fully charge a battery in under a minute. The scientists discovered that by coating lithium iron phosphate particles in a glassy material called lithium pyrophosphate, ions bypass the channels and move faster than in other batteries. Rechargeable batteries store and discharge energy as charged atoms (ions) form between two electrodes, the anode and cathode. Their charge and discharge rate are restricted by the speed with which these ions move. Such technology could reduce the weight and size of the batteries. A small prototype battery cell has been developed that can fully charge in 10 to 20 seconds, compared with six minutes for standard battery cells.[6]"

    I faintly recall at Paul's shop that they did measure the internal impedance of the lifepo4 battery banks and they were quite a bit less than lead acids. If that is so, we know what lowering the impedance does with the SG type systems - massive cables, etc... the results get better and better.

    I don't know how much testing has been done with cap dumps to the lifepo4 batteries either.

    The 7 transistor SG built to spec as the beginner's SG book shows, Peter and I can get it to run at top speed and draw as little as 1.3 amps, which is only 186 ma per transistor. At a C20 rate, that is around a 25ah 12v lead acid battery. For the equivelant capacity in the LiFePO4, that is around $275 or so on average. I did find some 20ah lifepo4 batts for around $125 but am getting more details and if it is what it appears to be, I'll probably get a couple to start testing. It is just a matter of time until these prices come down when they get popular enough.
    Aaron Murakami





    You never change things by fighting the existing reality. To change something, build a new model that makes the existing model obsolete. ― Richard Buckminster Fuller

  4. #4
    I think I may get some to experiment with too. They are darn expensive but aside from that they look so good!

    It seems to me like they may behave sort of like a super cap but with a stable voltage on the discharge. I played around with using very large caps instead of batteries on the front end because of their charging characteristics and some of the configurations I came up with were showing promise but in the end the voltage slope always becomes an issue for me.

    I also built some cells from scratch with lead and zinc and alum as the electrolyte. Those charged very fast both on mode one and on current popping but they were too small of a capacity to be practical for my needs. I was able to get them to self run with a back pop but only at a very low setting, I was charging little 9v batteries and AA's and drawing like 60ma on a solid state coil setup.

    I would like to try these LifePO4 cells and try again to back pop, or perhaps gen mode with it's natural tendency to push back on the primary could move this lighter chemistry to extend the run. Even if I cannot find an advantage in these ways I still love that they are so light and are dry cells. I already have a 3A tracker 5 so I imagine as long as I monitor the voltage it would work the same as the new ones with the pot tuned specifically for them. I bet the new models would do well for SLA's too, keep from drying them out.

    Thanks again, I will post if I get some of these to play with.

  5. #5
    Networking Architect Aaron Murakami's Avatar
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    Quote Originally Posted by BobZilla View Post
    I already have a 3A tracker 5 so I imagine as long as I monitor the voltage it would work the same as the new ones with the pot tuned specifically for them. I bet the new models would do well for SLA's too, keep from drying them out.

    Thanks again, I will post if I get some of these to play with.
    Yes, the lead acid trackers work fine for these and sealed lead acids - just disconnect at 14.8. And for these LiFePO4 Solar Tracker 5's 3a and 7.5a you're right - they're perfect for the sealed lead acids.
    Aaron Murakami





    You never change things by fighting the existing reality. To change something, build a new model that makes the existing model obsolete. ― Richard Buckminster Fuller

  6. #6
    Senior Member Tom C's Avatar
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    all of the trackers finish voltage can be factory set, I have a few models that are set for the lithium iron, both my 7.5 amps are set that way. and my little 3 amp also. I have 20 AH of lithium iron form Dakota Lithium. I ordered the trackers this way, they come with a different label showing the type of battery it will be set for.

    Tom C


    experimental Kits, chargers and solar trackers

  7. #7
    That got me thinking....

    Of course it would increase the cost but couldn't Mr. Bedini install two tuned pots and a double throw switch to make a charger that would handle both 14.8 and 15.3 cutoffs? That would be awesome.

  8. #8
    I ordered two 20AH packs to experiment with.

    I have been reading about these cells on a lot of RV forums and people have passionate feeling both for and against them. I will summarize some of what I have heard.

    The best thing I have found out is the chemistry does not sulphate which lends itself to storage use such as off-grid very well. If you were to go through a bit of cloudy days and could not get your packs charged back up fully they will not suffer the same sulphation problems that LA do. This is a huge advantage in my view. It also means that you do not have to "push" them all the way up as you do with LA because there is no danger permanent of capacity loss.

    Many of the suppliers are selling complicated cell balancing systems for these batteries which increase the cost a lot. If you are careful to check individual cells and balance them yourself from the start then you really don't need the expensive equipment which by the way is wasteful. These systems will intentionally burn off juice to let slower cells catch up to the ones that have peaked. Being that we are all trying to maximize conservation we don't want to burn off juice each and every time we charge for the sake of balancing the cells. i am not experienced with these cells so this is just personal opinion, if you want the extra circuitry than by all means I wouldn't discourage anyone from using it.

    The bigger point here is that since you do not have to "push" them to maximum to rid them of sulphation then if you keep them a little below max and do not run them down to 80% dod they could be slightly out of balance and it would not matter. Many people report that these cells actually last longer and perform better if you do not take them to 100% but I have no idea if that is true. I do agree that keeping within a reasonable margin both on the top and low end of charge should deal with any balancing discrepancy and who cares if there is no sulphation anyway.

    I believe this is why on the spec sheet for a single cell it says 3.8 max voltage but if in a series then 3.6 ,, they are allowing for that margin.

    Here is a sheet for the cells I have ordered, I actually have pre-built packs with 4 in series of these.
    http://www.batteryspace.com/prod-specs/6332.pdf

  9. #9
    there is a way to balance them without burn off, you can either recharge them all in parallel or you can charge each individual cell separately, with a switching array, eg with a two switch per cell cap pulser.

    these are good cells, good discharge rate without damage, only thing is they are expensive.

  10. #10
    @all

    I found this really interesting video which goes into great depth about the chemistry involved with Lithium cells of many flavors. It is a long presentation but for those of us who are really interested in this sort of thing there is a lot of information that is not widely distributed, especially about the doping methods.

    Also the information given really supports what I had already heard concerning the cells lasting longer if not pushed all the way. In short it is almost opposite of the problem we have with LA chemistry, with these as the voltage is raised it causes a buildup across the negative electrode from the electrolyte and positive electrode reaction. I think it is about 42 min into the talk when he gets to this but the entire video is a real gem.

    https://www.youtube.com/watch?v=9qi03QawZEk
    Last edited by BobZilla; 09-13-2014 at 02:55 PM.

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