Could LiFePO4 batteries be the way to go?

Discussion in 'Tech/Mech General' started by rogher, May 11, 2016.

  1. rogher

    rogher Funster

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    LiFePO4 is offering a performance benefit over Lead-Acid (wet/AGM/Gel) batteries in terms of weight and capacity.

    Where payload is critical you could make a significant saving by swapping to LiFePO4. It cannot be a direct swap, though, as you’ll need to change your charger: LiFePO4 do not like being ‘floated’ and need a controlled voltage for charging. I imagine that SP controllers may also need to differ.

    Does anyone have experience or plans to use them?
     
  2. Jim

    Jim Ringleader

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    RoadPro sell a lithium battery, it is excellent But last time I looked it was well over £2000. As good as they are, you can buy a lot of Victorian wet cells for 2k
     
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  3. StitchesnFluff

    StitchesnFluff Funster

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    Price will reduce over time, something for the future
     
  4. rogher

    rogher Funster

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    Yes, a French product, I believe. There are now many more versions available at much lower prices. The cheaper ones may not be as well constructed or protected with electronics. Sadly, that side has to be taken on trust. For around £700 you can get a battery equivalent to 170 Ah Lead-Acid and 1/4 the weight. That may be worth thinking about if you want to lose weight.
     
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  5. Gorse Hill

    Gorse Hill Funster

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    Not cheaper to go weight watchers (y)
     
  6. Gromett

    Gromett Funster

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    I was looking to build my own battery packs using similar techniques to what Tesla does. The batteries themselves can be had quite cheaply. The problem arises from the costs around the balancing circuits and the thermal management required to keep them safe.

    Boeing suffered major problems with their lithium batteries on the 787 Dreamliners. Tesla's techniques though have proven to be extremely safe. But the cost of those techniques are prohibitive for small self build battery pack unfortunately.

    There is also the additional problem of the voltage difference. I was intending to build a 12V regulated supply so everything in my van would work from 12V. Once I added up the costs it just proved too much for an experimental project.

    The cost of Lithium batteries has fallen dramatically and on their own are not cost prohibitive, it is all the extra stuff you need to safely charge, balance and protect that is the problem and those items probably won't fall in price too dramatically.
     
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  7. rogher

    rogher Funster

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    I think the technology has changed from the time that Boeing had their problems by the addition of Phosphate. They are now safe(r) and only 3.2V a cell, making four compatible with Lead-Acid. Besides being much lighter, they will (are said to) tolerate deep discharge much better so I’m thinking that big inverters will become more practical. Battery management is key. You must keep them balanced and some systems will do better than others. Those are likely to be the ones with the longer guarantee.
     
  8. Gromett

    Gromett Funster

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    There is a reduced risk of thermal run away with LiFePO4 but it is not totally removed. I would still recommend that the same protections are in place both physical and electrical. I did look at LiFePO4 but currently they are too expensive to consider.

    I forgot to mention, You would also have to swap out your solar controller as well.
     
  9. hilldweller

    hilldweller Funster Life Member

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    True. But in the context of 3.5 tonnes or more of MH how much benefit ? I have seen replacements for LA on sale now but don't recall the spec.

    A whole different matter on e-bikes, what a difference it's made to those.
     
  10. rogher

    rogher Funster

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    You could replace two 85Ah Gel batteries (54Kg) with one 100Ah LiFePO4 (14Kg) and gain 40Kg of payload. If you’re pressed for payload, that’s quite a bit extra leeway.
     
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  11. urban_biker

    urban_biker Funster

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    When the bring out the new Hymer B544 on a Tesla base vehicle then we should be OK. Although I bet the bastard campsites will charge a fortune for electric hookup.
     
  12. StitchesnFluff

    StitchesnFluff Funster

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    Just use solar?
     
  13. Robin McHood

    Robin McHood Funster

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  14. Techno

    Techno Funster Life Member

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    I have 200kg of batteries and just gained a 500kg increase in payload for £142 (y)
     
  15. Robin McHood

    Robin McHood Funster

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    Need to update that signature then :D
     
  16. NickNic

    NickNic Funster Life Member

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    Is there anything special about these particular ones or are they just the same as all the other Lithium batteries on the market?
     
  17. Techno

    Techno Funster Life Member

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    I'm not sending my V5 to DVLA until after my holiday (y)
     
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  18. Robin McHood

    Robin McHood Funster

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    There are a few different lithium chemistries out there. The LiFePO4 batteries are supposed to be safer but have a lower energy density than say the one in your tablet or phone. Beyond that I don't know a huge amount about them but Chris Dunphy's write up is worth reading for more in depth pros and cons. Must admit I envy him his bus though it wouldn't fit well on Scottish Roads:eek::eek:
     
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