Leisure battery an interesting website

Discussion in 'Tech/Mech General' started by SandJ, Feb 1, 2015.

  1. SandJ

    SandJ Funster

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  2. Techno

    Techno Funster Life Member

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  3. jonandshell

    jonandshell Funster

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    It's rubbish.

    Silver Calcium batteries are constructed to take the heat of rapid repeated charges and quick discharge.
    It is the heat which is the issue and requires the silver calcium support grids, not the depth of discharge.
    Industry still uses traditional open lead acid cells for a very good reason. They are economical and they work well.
    What is far more important than what is supporting the plate material is the plate material itself. Every deep discharge causes loss of plate material. The more of it there is, the longer it will last.
    Heavy batteries will last longer.

    The reasoning behind using a silver calcium starter battery in a deep discharge application is flawed and should be discounted.

    They are hardy the latest advance in cell technology either. They have been used by Ford for at least 8 years.
     
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  4. TheBig1

    TheBig1 Funster Life Member

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    what is normally more relevant is the reliability and cost. the absolute best I have seen for longevity of life are banner traction batteries, but they cost much more.
    a very good mid range alternative is the alphaline range of deep discharge batteries. very heavy lead plates and a 4 year warranty. prices are excellent too. £65 delivered for a 110ah. if they only last 4 years then that makes just over £16 per year, which to me is a bargain
     
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  5. funflair

    funflair Funster Life Member

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    I note that Varta don't recommend the silver ones themselves for leisure use so I agree RUBBISH.
     
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  6. Gromett

    Gromett Funster

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    Thanks for the Link SandJ, I am currently interested in this subject as I am in the market for a new set of batteries. However I got to this bit before giving up.

    At this point I knew for a fact that I couldn't trust the article. Lead batteries are 97% recycled. In fact they have the best recycling record of any consumer product bar none. In the US the figure is 99%. This far exceeds the recycling level for any other battery and with lower environmental impact as well. Lead is much easier to recycle than say Lithium Polymer or Nickel Cadmium and is better environmentally in the initial production..

    Secondly, As someone else has already stated in this thread. Every cycle a small amount of the lead is used/lost so therefore the more of it the better.

    As for the premise of the article that it is kinder to the battery charger. I agree in some respect I have had a cheap charger fail because of a battery fault. But this was a £500 VRLA AGM battery. Top of the range and it lasted almost 8 years of heavy use. The charger was an el cheapo. The battery I believe developed a short internally or similar problem so the charger was permanently on trying to charge the battery. It burnt out a mosfet. I blame this on the charger. The charger should have detected it's own temperature was at detrimental levels and taken action to protect itself. My new charger is a 50Amp one from Sterling which I am sure would not fail.

    Anyway, I have lost faith that anything this article says is accurate. I will stick to the heaviest battery by a quality manufacturer I can afford. I will continue to ignore clever advances in this most basic of technologies. I will continue to avoid Gel batteries.
     
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  7. Gromett

    Gromett Funster

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  8. Wissel

    Wissel Funster

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    Think you have lithium on the mind today :)

    This is the way I'm going to go. More expensive I know, but if you have a 100Ah battery you can use most of the 100Ah (what is it, 50Ah on a normal 100Ah battery?), lighter and they can be charged a lot faster.

    I think as a work solution that means not having to be on hook-up, the price is justified.

    Thoughts?
     
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  9. Gromett

    Gromett Funster

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    The two advantages most people quote is weight and usable capacity. From a 100AH battery you get 50Ah usable from lead, and 85AH from Li... Between a quarter and a third of the weight which is important for us and for EV's.

    But there are other factors that I like as well. Round trip efficiency. With a lead acid battery you can only get out 85% at most of the energy you put in. With Li you get close to 100%. This is especially important for Motorhomes running on solar. That is an extra 15% usable energy on top of the 35% from moving from lead to Li.

    Then there is charge speed. You can charge an Li battery much faster than a Lead battery without cooking it. And with Li it is a straight forward 2 stage charge not 3+ stages so faster on time as well.

    Finally there is the number of cycles. With lead depending on who you believe you can get between 300-500 full charge/discharge cycles out of a battery. With a lithium it is counted in the 1,000's Anything from 2,000 to 5,000 are quoted. Lets pick the middle figure and just say 2500 and lets pick the best case for a lead battery of 500. This is 5 times the number of cycles... So an Li battery will last 5 times longer, so even though the up front cost of an Li battery may be higher, it provides much more utility, is more efficient and lasts a lot longer. You also gain some minor fuel efficiency from not carrying so much lead around and free up quite a bit of space.

    I am loving Lithium and over the last 6-12 months it has come into my price range.

    These are the ones I am looking at.

    www.ebay.co.uk/itm/271946863054

    Out of stock at the moment. But four of these and use the bottom balance technique you can run them extremely safely in a motorhome as the leisure battery.
     
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  10. Wissel

    Wissel Funster

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    That looks seriously cheap compared to what I've been looking at.

    I started with EZA (from memory) at about £2.3K for 130Ah (again from memory) and so far down to the Victron 160Ah at about £1500.

    Do you have the voltage and size of the ones you linked to?

    Also assume they need some kind of BMS but guess you have probably looked into this and charging?

    Would love to hear your thoughts on a complete lithium solution when you have a few minutes.
     
  11. Gromett

    Gromett Funster

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    ok. All LiFePO4 Batteries have the same (practically) voltages. The nominal voltage of a LiFePO4 (LFP from now on) is 3.2V. So 3.2 * 4 = 12.8 which pretty much matches our lead acid batteries.

    Here are the specs for the batteries.

    Capacity: 100Ah, size: 221x142x61 mm, weight: 3.1 kg. Model: SP-LFP100AHA

    Nominal voltage of the cell is 3,2 V and the operational voltage is 2,8 - 3,65 V.
    The maximum charging voltage for initial charge is 3,7 V.
    Recommended subsequent charging is to 3.65 V.
    The minimum voltage is 2.65 V.
    Maximum discharge current is 3C continously.

    The charge voltage to take them up to 100% State of Charge (SOC) is 3.65v which x4 = 14.6V which is .1v higher than the maximum voltage I use on my current lead acid bank.

    The problem with LFP batteries is that if you just put 14.6V across the entire bank you will have serious issues as one cell may reach 3.65 before all the others and will then go over voltage before the entire bank has reached 14.6V. This is where a BMS comes in. What this does is connects a shunt resistor across the cell that reaches 3.66V until the voltage falls back down again. This is repeated until all cells reach the full 3.65V level.

    This is called top balancing. It is also what reduces the lifespan of LFP batteries. Lead batteries like to be fully charged and kept topped up. LFP batteries don't like this.

    When an LFP battery comes off the line it will have at least the capacity specified (often more). But it will probably be no where near the one before it on the production like or the one after it. This becomes a problem during discharge. If one cell in your bank has a much lower capacity than the rest in your bank you will end up with that cell falling below it's minimum voltage before the entire bank has reached cutoff voltage. In extreme cases this can cause a reverse voltage on the terminal and destroy that cell.

    So. What has been recommended to me is that we use bottom balancing. Basically we discharge all the cells in the battery independently down to our cut off voltage, Then connect them into a bank and charge the entire bank up to the full charge voltage. This way we are giving all cells and equal quantity of charge. This does mean that some cells are not being taken to 100% SOC, however this is not a bad thing if it extends the lifespan massively of the entire bank.

    One gentleman who used to use top balancing and tried to achieve maximum capacity out of his LFP battery bank started losing cells after 12-18 months and ended up going back to Lead batteries until he heard about bottom balancing. Since then he has had a bank running for 5 years and is still at around 95% capacity.

    So what I will probably do, is bottom balance my cells. Then charge to 13.8v (3.45V per cell) which is the max charge voltage of my solar controller. I will set the cut off voltage of my bank at 11v ( 2.75V) which is well above the 2.65V per cell minimum. Because I am operating well within the range of voltages I should seriously extend the lifespan of the bank, and it will simplify charging and safety cutoffs. It also means I don't need a shunt style BMS.

    So my current system is a sterling 12v 50Amp charger which does have programmable profiles. So I will set it to 2 stage charging by setting the absorption voltage to 13.7 volts. My solar controllers max voltage is 13.8Volts which is bang on what I need. So all I need to do is install a LVD device. You can buy Low Voltage Disconnect devices pretty cheaply, however I am tempted to create my own using an arduino which will include a per cell voltage monitor...

    Anyway, That is roughly what I am thinking at the moment.

    Please excuse any errors, grammar, spelling or fact based as I just typed this in quick before I start work.

    Do a quick google for bottom balancing... EVTV has some videos which I have queued to watch but haven't watched yet.
     
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  12. Happy1

    Happy1 Funster

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