Lithium house bank. Affordable from China?

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

  1. DennisRB
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    DennisRB Senior Member

    I have heard the prices are coming way down for lithium batteries from China. Does anyone have any sources/prices or knowledge on quality?
     
  2. BertKu
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    BertKu Senior Member

    I feel always sorry when I don't get at least one reply to my questions, thus let me give you my opinion. At least you should feel better now.
    If you have a battery bank of 220Ah and 12 Volt i.e 2640 watt, one could at present make one up with 25 battery packs of the cheapest type from HobbyKing (www.HobbyKing.com) and that is the cheapest at present offered in China.
    Each 5 Ah / 6 batteries in series i.e. 19.8 - 22,2 Volt cost 39 USA Dollars and that would mean 106 watt x 25 = 2650 watt. I am convinced that your bank is still less than 25 x 40 = 1000 USA dollar + shipping. (I ignore the voltage and compare only the power output for price comparison)
    I bought some time ago 40 Heavy duty Lithium batteries as an experiment and charging a battery bank of multiple lithium batteries is still a nightmare and cumbersome. Jeremy Harris gave me some solutions, but this balancing thing and ensuring no battery get overcharged is a problem when one has large battery banks of more than a few kilowatts. Special on a boat.
    Bert
     
  3. BertKu
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    BertKu Senior Member

    Dennis, here are a few addresses I have been dealing with.
    www.ewtbattery.com , Global Sources Product Alert [paservices@globalsources.com] and EEMB Batteries, Group9.

    Group9 is making large 24, 36 and 48 Volt > 10 kwh batteries banks for the Telecoms industry, I doubt it that they will have come down in costprice. Their quality is very good.
    Bert
     
  4. Red Dwarf
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    Red Dwarf Senior Member

    You may want to look at the pack from a Toyota Prius. It is about $2000 for 6.5Ah at 288v and weighs 68kg.

    You could either step down the votage or rewire the modules in the pack. I would rewire the modules as it is easy to do.

    The advantage of the Prius pack is it is mass produced in the millions so price and availability are good.
     
  5. BertKu
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    BertKu Senior Member

    Good point, but 6,5 Ah x 288 Volt is only 1,872 Kwh and that seem to be a little low for a car that size. Also 2000 USA dollar for 1.8Kwh versus 2.65 Kwh for 1000 dollar. Could it be 65 Ah per battery string? Or are there many 6,5 Ah batteries parallel? i.e. only one string is 1.872 Kwh. ( 80 batteries in series of 3.6 Volt)

    Still, charging is still not an easy matter when hundreds of batteries are in one pack.
    Bert
     
  6. DennisRB
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    DennisRB Senior Member

  7. BertKu
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    BertKu Senior Member

    Is Alibaba not a "used item for sale website? ". The fellow must have figured out that it is a nightmare. Lithium batteries are fine for Telecoms, they have enough space for millions of wires for balancing and measuring. But on a boat it is much more difficult. Porta gave me the solution to use rare earth magnets between my 40 Li batteries. It works well, in view that I do not charge them on the boat, but remove them and charge them in separate single charging stations at 10 at the time. I may in future create a different charging station to do all of them at the same time, but still single charging for the time being.
    Bert
     
  8. DennisRB
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    DennisRB Senior Member

    I didn't know it was such a hassle to charge them. I have never used Alibaba. But it seems to always come up when I search for lithium batteries. If you read most of the adds it appears the batteries are brand new from China and many have huge minimum orders.
     
  9. BertKu
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    BertKu Senior Member

    The best example will be.
    You take 20 NiCad, or NiMH batteries and make 20 columns. i.e. 400 batteries.
    If you have one battery faster discharging than somewhere in another column, not a problem. It somehow sort itself out. If one battery goes flat in total, all what will happen the other 399 batteries take over and balances itself out untill recharged or untill you have discovered this bad boy and recharge this one in full. But even after 5 years you did not discover this bad boy, it is still not really a big problem.

    If you take 20 x 20 Lithium batteries,which is not allowed that any of those 400 batteries shall fall below 2 Volt each (otherwise that particular battery is internally damaged) it means you need 400 wires to do balancing and measuring. Jeremy Harris proposed to have 20 parallel and thus you have only to worry about 20 wires, but still you have to ensure that none of those 20 paralleled columns are falling below 2 Volt. Group9 gladly sell you fantastic batteries, no doubt about it. However you must make your own charger. That tells all. Bert
     
  10. BertKu
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    BertKu Senior Member

    Dennis, at one stage I made a system whereby I divided the 5 columns with 8 x LifePO4 batteries each into 3 sections per column. Thus instead of 40 wires, I had 3 x 5 = 15 wires. What I did, I broke each column into 3 sections, 2 batteries, 3 batteries and 3 batteries. Then I compared the 3 sections with each other. In the microprocessor I divided/measured the 3 sections and if any of the results was out by more than 0.5 Volt, I had to take that column apart and checked for a bad battery, but I could not balance and still had to take the batteries out and single charged them fully.
    I did not have time anymore to follow Jeremy Harris solution up and should have 5 batteries connected parallel, with then only 3 wires. i.e. I should have compared 3 sets of 5 batteries parallel , with the other 3 sets of 5 batteries and calculated/compared with the 2 sets of 5 batteries. I could then have 40 batteries with 3 wires, but could not really verify the balancing of those the sets of batteries, thus I gave up, in view that I did not have the time anymore in experimenting the long term result. Bert
     
  11. CDK
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    CDK retired engineer

    Yes, fast charging lithium batteries is cumbersome. A Makita 18V pack is connected to the charger with a total of 10 pins! But the charging time for an empty pack is only 22 minutes, that puts the charging current somewhere around 2.5C or in this case 5 amps.

    Treating a 100 Ah LA battery in a similar manner would require 250 Amps charging current. Even with test leads to every cell it would probably end in a Big Bang!

    A 12V house battery would need just 5 wires for controlled charging. And because lithium batteries can be used until they are almost completely discharged, you can replace 200 Ah LA with 100 Ah Lithium.
     
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  12. BertKu
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    BertKu Senior Member

    Most likely.

    Very true, sadly the problem is that one needs to make sure that none of the batteries goes below 2 Volt and for up to 6 batteries, that is fine, only 6 wires (included mass) , but as soon you play with Kilowatts, that is a different story. Funny, I tried to obtain a LiFeP04 charger for large battery banks. Not available. Large 100 - 200 Amph Batteries and banks, plenty. (at a price) Bert
     
  13. DennisRB
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    DennisRB Senior Member

    Thanks guys very interesting. So I take it each cell needs to be treated seperately or at minimum in parallel not series. So I take it each cell is 2V? So you really need 6 x 2 Volts chargers?
     
  14. CDK
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    CDK retired engineer

    No Dennis, each cell is a bit over 3V but must not be discharged below 2V to protect it against damage.
     

  15. BertKu
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    BertKu Senior Member

    Hi Dennis, every Lithium cell has between 3.3 Volt and 3.65 Volt when fully charged. It depends on the chemical content of the Lithium. Per example a Lithium with Fe will be about 3.35 Volt each cell. This type, LiFePo4 I have to charge until it reaches 3.65 Volt. If I go over this level, you reduce the lifetime drastically of such battery. Others are fully charged 3.6 Volt and need a higher as per manufacturer charging Voltage. The 2 volt is the lowest voltage such battery is allowed to go. Thus you cannot ever discharged Lithium batteries to zero like the NiMH or NiCd batteries. If you are not an electrical/electronic Fundy, get a proper charger matched to your Lithium battery bank, you will otherwise most likely waste a lot of your money.
    Bert
    P.S. Having Lithium batteries switched parallel and then being charged was a good solution from Jeremy Harris, provided you have an electronic circuit regulating the steps needed to charge such parallel string. i.e. charging with max 5C , this means if the manufacturer specify 5 C and C= Ah rating of your battery. Thus a 20 Ah battery and specified as maximum 5 C , can be charged at 100 Ampere. Should you have 5 parallel, you need maximum 500 Ampere. At a lower rate, it takes longer . As soon it reaches 3.6 Volt, you change the charging mode to Voltage low leakage charging and not high current charging.
     
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