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lowest cycle cost battery

Discussion in 'Electronic Design' started by colin, Mar 24, 2007.

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  1. colin

    colin Guest


    Whats the cutting edge in lowest cost per kwh of 'cycled energy' storage
    these days ?
    ie the cost of 1khw storage / cycles in a liftime ?

    SLA are quite cheap, but dont last so long,
    nicad more expensive but probably more cycles,
    Im not sure about the other types lithium etc,
    as theyr not readily available off the shelf so hard to get a good cost to
    maybe super cap?

    I had a crazy idea to work out economics of storing electricity at cheap
    rate and be able to use it during the day.
    plus it would be a good ups.

    A water tower might be good if there was one handy.

    Colin =^.^=
  2. Jeff L

    Jeff L Guest

    If properly taken care of and not deeply discharged, they can last a very
    long time (there are some in service for 20+ years and usually only get
    changed due to routine maintenance).

    What you ask is difficult:
    1) since some batteries such as Li ION age whether they are used or not.
    2) it depends on how much they are discharged. A lead acid will survive a
    lot longer and store a lot more energy if discharged only 20% compared to
    80%. In other words adding capacity to a batter bank for the same load and
    charger will exponentially extend the life of the batteries
    3) how well they are charged. Some charger algorithms are very abusive,
    while others help extend life
    4) temperature at which they run.
    5) Quality of the cell
    6) many other not as significant variables
  3. Eeyore

    Eeyore Guest

    Even better when it rains ! Free power.

  4. colin

    colin Guest

    well the numbers for SLA dont add up favourably,
    wikipedia quotes 7-18WH/$ with a durability of <1000 cycles
    so thats 6c per khw wich is more than the cheap rate savings.

    seems the other types come out worse.

    Colin =^.^=
  5. John Barrett

    John Barrett Guest

    I'd compute it based on years of service -- do the numbers for 5,7, and 10
    years average battery life and see where that puts you -- as long as you are
    not deep cycling the batteries -- you will get more cycles out of them --
    which is why I keep talking about oversizing the battery bank.

    I've got one 7 year old bank that is regularly discharged to 25% and
    occasionally to 50% (2-3 times per month) that is still going strong... I
    dont anticipate needing to replace any of the cells for at least 2-3 more
    years.... (based on "new" cells charging to 12.8v and the worst cell is the
    bank is currently topping out at 12.6v)

    the key is a VERY good charging circuit to maintain the battery health and
    avoiding deep discharge

    since you are talking about an off-grid application, dont forget to include
    the cost of inverters in the cost estimate.. and seriously consider running
    the banks at 48V which will require charge balancing -- which was discussed
    in another thread a few days ago.
  6. colin

    colin Guest

    well it would be 1 cycle per day,
    as its storing cheap rate electricity every night,
    so 1000 cycles is ~3 years,
    yes I apreciate what you said about under utilising,
    and this may decrease the cost per kwh cycle significantly,
    but ive not seen any figures to go on.
    also I havnt started to consider anything financial like return on capital
    or cost of equipment wich presumably would outlast the batteries many times
    as it doesnt look like the batteries are even going to break even.
    I think it needs to be closer to around 1c per kwh of storage to make it
    if it was this cheap then the power companies would probably be using them
    for this very purpose anyway.

    ofc if the inverter isnt pretty efficient it will throw away any benefits.

    Colin =^.^=
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