Lithium Ion Leisure batteries.

Discussion in 'Motorhome Chat' started by Gromett, Feb 5, 2016.

  1. Gromett

    Gromett Funster

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    I have looked at these before and was put off by cost and fire risk but I have recently started looking at them again.

    The advantages are;
    They charge at a constant rate. When you charge a lead acid battery the bulk stage is fine but when it gets to the absorption stage your solar panels output current is not totally used and is therefore wasted. When you charge a lead acid battery it is at best 85% efficient a lithium battery is 99%. So you get more out of your solar panels.

    A lead acid battery needs to be regularly fully charged to maintain its capacity. A lithium based battery can run between 50%-95% and anything in between without needing a full charge.

    A lithium battery happily works on a depth of discharge down to 85% whereas a lead acid battery only gives 50%. So a 100AH lead acid is effectively only a 50AH battery a 100AH Lithium based battery is 85AH.

    A lithium based battery is less than half the weight usually for it's rated capacity . So you can either have twice as many for the same weight or have less weight for the same capacity. Please see previous paragraph though.

    A lithium battery doesn't suffer from Peukert’s losses. So if you pull a large current for an inverter you don't lose the capacity of the battery like you do with lead acid.

    A lithium based battery appears to have a lifespan in excess of twice the number of cycles of a lead acid battery if not more.

    Finally the fast charge rate. If you have charger capable you can fully charge a Lithium battery in half an hour and the charge rate doesn't slow down.

    ok. The downsides are they cost a bleeding fortune which is where this post comes in.
    I have been looking at a lot of youtube videos where people have been using 18650 batteries to make battery packs for their e-bikes. I am now looking into doing the same using batteries from recovered laptop batteries.

    I am aware of the need for BMS and specialised charger etc etc.

    I am just wondering if anyone else on here has done anything similar before. Also thought it might make an interesting thread for people who are interested in the techy stuff.

    @Techno I don't know why you but your name popped to mind :p
     
    Last edited: Feb 5, 2016
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  2. Gromett

    Gromett Funster

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    There are quite a few videos on youtube. but this guy has done a series. This one is worth a watch.


    He creates a battery bank to power his VW camper van using recovered laptop batteries..
     
  3. Gromett

    Gromett Funster

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    I am looking at building lot of small packs of 20 batteries in each using a pair of these for each one.

    http://www.ebay.co.uk/itm/262123820960

    20 batteries at 2Ah (2,000mAh) gives 40AH at 3.7 V. I would need 3 or 4 of these packs in series to give me the 12V. I am still trying to figure out if I need 3 x 4.2V or 4 x 3.7v depending on whether you measure the nominal voltage or max voltage. Research on going.

    But if I use 4 that will be 40AH a pack and require 80 batteries. I am looking at paying no more than 50p a battery so total cost £40.

    A 100AH lead acid will cost me about £100 but will only give me 50AH. so that is £2/AH of usable. If I can get the used Lipo batteries at 50p each and get 80% usable capacity I am looking at about £1.20/AH usable.

    Check my maths someone please :p
     
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  4. Snowbird

    Snowbird Funster Life Member

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    I converted 2 mobilty scooters from lithium batteries to SLA. I have 3 Lithium chargers here if they are any good to you. The downside is they are 24 volt, but are freebies.
     
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  5. Terry

    Terry Funster

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    Save me one of them Dave (y) No Idea what I will do with it yet but if it's for free I will figure something out
    terry
     
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  6. Gromett

    Gromett Funster

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    I will be doing these at 12V. I already have an expensive 50A sterling charger which has profiles for Li batteries. Thanks for the kind offer though (y)
     
  7. Snowbird

    Snowbird Funster Life Member

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    They are yours pal. Am having a clearout whilst am home.
     
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  8. Techno

    Techno Funster Life Member

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    Lithium is only held back by the price. Leisure batteries are best thought of as best bang for buck.
    I'm using Lithium Polymer batteries in my Lego models but a 7.4volt battery weighs a few grams and costs £42.99 :ROFLMAO:
     
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  9. Gromett

    Gromett Funster

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    I am looking at using recovered cells from laptop batteries. I have 3 bids on ebay for job lots at the moment. Currently the bids are at < 20p a cell.
    I need 80 Cells to make a 40AH battery in 4s20p format. At current bids this would be £16.... I doubt I will get all my packs that cheap but I should get a couple.
    Even at my upper limit of 50p that still works out £40 if my maths is correct?

    There are loads of these batteries coming to market now and every single youtube video I have seen has had the vast majority of cells still giving between 2.2 and 2.4 AH of remaining life. I am basing my calcs on only getting 2AH per cell.
     
  10. Lee Fryer

    Lee Fryer Funster

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    @Techno have a look at hobbyking they are a lot cheaper.
    Lee
     
  11. Ralph-n-Bev

    Ralph-n-Bev Funster

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  12. Dazzlin

    Dazzlin Funster Life Member

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  13. Techno

    Techno Funster Life Member

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  14. Ralph-n-Bev

    Ralph-n-Bev Funster

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    Its worth getting VAT registered if your having two :LOL:
     
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  15. Lee Fryer

    Lee Fryer Funster

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    Sorry thought they would hidden in battery box.
    Lee
     
  16. Gromett

    Gromett Funster

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  17. Gromett

    Gromett Funster

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  18. Steve

    Steve Funster Life Member

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    As you know lipo cells are 3.7v so x4 = 14.8v. may be a little high for a 12v system. And lipo cells keep a steady voltage for nearly all their capacity. Unlike a Lead Acid. I have quite a few lipos of various cell sizes which I use on my rc trucks. When you start mixing cells things can go wrong with a bang and a nice fire (done that) There are lipo 12v car type batteries on the market but the price is still high. But it’s the BM side that will really cost. I have had a play around with some of the bits I have and the charger I have needs a pc to run it. You only need a cell to have the wrong resistance and things get hot very quick. Please be careful and NEVER leave them charging unattended. But its good fun being a kid again.:)

    Steve
     
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  19. Ralph-n-Bev

    Ralph-n-Bev Funster

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    Yeah...But you do get 360Ah

    Its some beast as well 662 x 197 x 355 mm
     
  20. Ralph-n-Bev

    Ralph-n-Bev Funster

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