Lithium house bank. Affordable from China?

Discussion in 'OnBoard Electronics & Controls' started by DennisRB, Nov 14, 2012.

  1. CDK
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    CDK retired engineer

    The 9.6V Hilti could be 3-cell lithium, but I assume you are correct Bert, it will be NiMh or NiCd.
    Squid also is correct that you get what you paid for. My Makita drives so many screw and drills so many holes on one 18V 1.3Ah battery that I tend to forget it is cordless. It even rips the head of a screw if the torque setting is wrong.
    And then suddenly within no more than a few seconds, without previously loosing torque, it is all over and I understand why the put a 2nd battery in the box. It may have been charged one week ago or 6 months, that doesn't matter: it stays fully charged indefinitely or so it seems.

    I still need to find out if the used battery really has lost all charge or if there is mosfet and a voltage monitor hidden somewhere in the battery pack.
     
  2. BertKu
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    BertKu Senior Member

    Yes, you are right. The Hilti has 3 Lithium batteries in them. What Squidly-Didly most likely has as a problem. Those batteries need to be charged the first time for a very long time. But all my Ryobi tools have given me very good service, the Lithium as well as the Nicad's, Thus I assume that we have a "first time" start up problem. Well , let see what Squid has to tell us.

    CDK, have you tried, just to leave your "dead" battery on the charger for 1 day.? If the Voltage was dropped below the 2 Volt level, your are most likely correct and a simple electronic circuit gives the battery a chance to stay for a few weeks at low voltage, without being damaged, until recharged.
    Bert
     
  3. CDK
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    CDK retired engineer

    No, the battery slides on top of the charger covering all contacts, so there is no way to measure voltages. The charger (much larger than the power tool itself) speaks "beeper language" and signals with leds whether or not the battery qualifies for a charge. If yes, the internal blower starts and charging is accomplished in 23 minutes for a "dead" battery at room temperature, or less for a partially discharged one. At the end of the cycle the beeper says the battery is ready and a green led flashes; the blower remains switched on until the battery is sufficiently cooled off. Nothing else happens if I leave the battery on the charger, there may remain a trickle charge or not, I do not know.
    Placing a full battery on the charger results in another beeper "word" without even trying to charge it. The vocabulary and volume can be altered in case it is confused with a cell phone ring tone but I lost the manual, so I do not know how and do not care.
    The text on the device says it charges any battery lithium pack over 7.2V regardless of capacity, provided it is in good order. It does that by sensing each cell and comparing cell voltages before attempting to charge (I guess, that is the way I would program it).
     
  4. BertKu
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    BertKu Senior Member

    Yes, they make some very clever designs. A microchip cost nothing anymore in volumes today . It probably balances the number of batteries placed on charge, , even when the number of cells are unknown and thereafter start charging. Clever software. Love to see their Algorithm. I see it is overcast at your place, you must be relieved.
    Bert
     
  5. DennisRB
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    DennisRB Senior Member


    Groper, most of this is pretty much what I was trying to say earlier in the thread! Regular chargers/alternators will not require a constant current ability unless the current is high enough to overload the lithiums, which I would guess would not be an issue in almost every case where lithiums are replacing LA.

    I think a fairly simple charging system can be used without huge changes to the charging facilities most of us already have. Since it has been shown in practice that imbalances are not really an issue when the Lithium batts are used as a regular house bank a simple voltage sensing alarm/output can be used for dangerous imbalances for each individual cell. This would not be expensive for a reasonably competent DIYer to set up.

    For a more advanced system which is still very easy to implement, you regulate charge output when the cell with the highest voltage reaches your pre determined max based only on that cell. The other cells may balance each other automatically under this system after some time of float charging otherwise you may need to do it manually every now and then.

    For low voltage protection you would have an alarm/isolation contactor that goes off when the voltage reaches the lower limit based on the reading of the lowest cell.

    Bert mentioned possible issues when you are also drawing large house loads while charging. But I can not see why this would be an issue any more than with LA batteries unless again, your charger is so powerful that it can supply more current than the max rating of the batteries.

    Also cells in parallel will balance each other so I cant see why it would be all that bad to parallel them.

    The CF thread is worth reading. Here is the results someone had using a 14.4V charge with new batteries. The cells were out of ballance and they appeared to ballance themselves quickly without individual treatment. I'm still reading the thread and it seems to have a lot of good info.

    [​IMG]
     
  6. BertKu
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    BertKu Senior Member

    First at all compliments of the season Dennis, may you all have in Australia (and the rest of the world) a pleasant relaxing time.

    Fully agree, when you have a battery bank consisting of large 4 single cells.
    Like I have said before, whatever one is doing, something has advantages and disadvantages. In my case I prefer to keep the charging separate of consuming energy, and have the batteries charged in single 3.65 charging stations. However not everybody can charge their batteries in a single mode, and remove them from the battery bank. But you are right, in most cases a simple slow charging system will do.
    again provided you dealing with 4 single cells (or multiple cells parallel, behaving as a single cell) and each cell has its own floating monitoring system. Fed by the cell itself. I.e. a low voltage sensing device using very low current with a opto-coupler to a central alarm circuit. Or a resistor bank and than monitoring with a micro the various levels. Bear in mind you need to monitor each large cell. O.K. one could do it with 4 separate alarm units. As soon one has a multiple battery packs parallel and in series, unfortunately it will get complex. (I do not mean 6 cells parallel and then 4 of them in series)
    Yes, per example you have solar panels which can provide plenty of current and you reduce your house load to a minimum. Most LiFePo4 batteries prefer to be charged at 1C, except the nano technology, you are able in that case to charge with high currents.
    agreed.

    Very nice graph !!.
    Bert
     
  7. DennisRB
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    DennisRB Senior Member

    Merry xmas to you too Bert! I have been in Scotland with my girlfriends family rather than in sunny Australia. I'm in Isle of Mann right now.

    Considering the price of a lithium house bank I think it would be a sensible option just to use a BMS when they are only $75!

    http://minibms.mybigcommerce.com/products/HousePower-BMS.html

    I really think it will not be a problem to replace LA with Lithium in an average boats house bank. So now the question comes back up to, how cheap can we get the cells? An old workmate of mine now owns a marine electricians workshop and can get me AGM 12V 90AH cells for $70, so I guess it would be a no brainer for me just to get those. But I still want to explore the possibilities of lithium.
     
  8. groper
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    groper Senior Member

    Yep agree dennis, the only modification needs to be a slightly lower charge voltage.

    14.4v is too high to keep a 12v nominal lifepo4 battery healthy, to adapt from a lead acid system reduce the charging voltage to 13.8V and everything else can stay the same, they are a drop in replacement so to speak.

    i dont see the charging current as an issue except in some very unique situations... a typical house bank on a cruising boat would be between 300-800amp hours @ 12v nominal. This means youd have to have method of charging that would exceed 1C or 300-800amps respectively. With most alternators working under 150amps, and your typical solar system under 1kw, or 80amps, its pretty difficult to get anywhere near, let alone exceed, a 1C charge rate.

    I understand bertku is using them for propulsion, so his situation is kind of special.

    Again, the reason we see the big names talking about constant current charging before swtiching to constant voltage charging, is for a fast charger like the type you expect with a cordless drill. ie. -You need the battery charged fast, and you will cycle the battery deeply, and thus you also need good cell balancing with every charge also. Same goes for the hobby guys and the electric vehicle guys and electric propulsion (boat) guys...
     
  9. groper
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    groper Senior Member

    Ive already made the desicion to go with lifepo4 on my boat, the main reason is because i will save at least 100% of the weight and space.

    In australia, you can buy the cells for between $1.10 - $1.50 per amp hour from the electric vehicle suppliers like ev-power or ev-works etc. Alibabba quotes $1.20-$1.50USD to buy from china in small quantities. So its about the same unless you can get together a bulk order where they offer a discount. Seems to be about the same in europe and the US, most people seem to be paying around this price. If your happy to wait, i think over the next few years these cells will get cheaper and cheaper relatively speaking, and eventually lead acid cells will fade into oblivion as a thing of the past...
     
  10. DennisRB
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    DennisRB Senior Member

    I wont need them for at least 3 - 4 years. I just finished a year cruising and need to spend some time working. But this will give me plenty of time to get my boat ready for a 4 year cruise this time. So I hope cost will come down a lot.

    Are your quoted AH prices in 12V or 3V? I can get AGM for 75c/ah @ 12V today. My batteries are good enough to last a while so I don't need to buy urgently.
     
  11. groper
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    groper Senior Member

    I quoted price per 3V cell... so @ 12V nominal, looking at around $4.40 per amphour - still much dearer than AGM, but much lighter and has much more usable capacity, due to deeper charge discharge cycle without damaging the battery - so if you need 400amp hour bank capacity in lead acid, youll only need about 200amp hour in lifepo4... couple with longer life, more cycles, the price is actually very comparable. The reduced weight and space is the icing on the cake...
     
  12. BertKu
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    BertKu Senior Member

    Hi Groper and Dennis,

    Here some pictures of my 8 x 5 configuration. Please note the tape to keep the batteries in place when lid is placed back. Also I have a few batteries which were overcharged to 3.9 Volt in 2011 and still can't see any problems. Also one whereby the voltage had dropped to below 2 Volt. Also that one is still working without any noticeable damage effect. Please also note the powerful magnet between the batteries to ensure proper contact (solution Porta) and to allow me to replace a battery or to remove a complete string for charging without shutting the prop down. In such battery configuration I could go to 400 or 500 batteries easy in this kind of pipe system.

    I fully agree with both of you, the charging is absolute not a problem. It is monitoring the lower and upper single battery voltage what is the difficult part. I am a strong believer, because I am charging each battery in a single charging station, all of them in the same 0.5% accuracy , I don't have to be worried about balancing, because as soon I am charging the batteries, they are all balanced. Groper I also hope that the cost of good Lithium batteries will come down. Bert
     

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  13. wasafari
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    wasafari New Member

    Probably this source http://www.ev-power.eu could be helpfull. You can find LiFePo4 cels, BMS and all terminal connectors etc. Read the blog there are some practical solutions. As to price level bank of 600 Ah (made from 200 Ah Winston cels ) including BMS and controller is about 3000 EUR (I am in EU). So you could compare this with "fantastic" price levels for three times smaller banks of some manufacturers (nice boxes?:).
     
  14. boradicus
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    boradicus Senior Member

    Interesting set up

    What are you using for a charge controller?
     

  15. BertKu
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    BertKu Senior Member

    Hi boradicus,

    I'm sorry for the delayed reply, I was in the hospital for an op. Thereafter some time in bed. Will make some photo's this week and post them. Give me some time, bert
     
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