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  1. 06 Apr '15 18:21 / 6 edits
    I presume it would generally have a lower energy density than lithium-based batteries but it is safer than lithium-based batteries because aluminum is much less reactive than lithium and doesn't readily burst into flames if the metal is exposed to air/moisture:

    http://phys.org/news/2015-04-ultra-fast-aluminum-battery-safe-alternative.html

    But what has really got my attention is where it says:

    "..In addition to small electronic devices, aluminum batteries could be used to store renewable energy on the electrical grid, Dai said.

    "The grid needs a battery with a long cycle life that can rapidly store and release energy," he explained. "Our latest unpublished data suggest that an aluminum battery can be recharged tens of thousands of times. It's hard to imagine building a huge lithium-ion battery for grid storage."
    ..."

    For stationary off-the-grid energy storage like this, the energy density isn't usually a big issue like it often is for mobile storage.
    I wonder if this could be the stationary off-the-grid energy storage for the future?
    I guess that at least in part depends on the energy efficiency of its charge-discharge cycle but, frustratingly, the link gives no clues or mention of that energy efficiency. If the energy that is wasted can be made to be very small, say just 2% of the energy going in and out of storage, we may decide we can live with that. But if the energy wasted is going to be very large, say 40%, I guess that would be considered unacceptable and we would use a more energy efficient method to store off-the-grid even if the set-up costs are much more expensive (possibly use superconductor ring storage that stores the energy as magnetic energy )
  2. Standard member sonhouse
    Fast and Curious
    06 Apr '15 18:43
    Originally posted by humy
    I presume it would generally have a lower energy density than lithium-based batteries but it is safer than lithium-based batteries because aluminum is much less reactive than lithium and doesn't readily burst into flames if the metal is exposed to air/moisture:

    http://phys.org/news/2015-04-ultra-fast-aluminum-battery-safe-alternative.html

    But what has rea ...[text shortened]... energy efficient method to store off-the-grid even if the set-up costs are much more expensive.
    Usually the energy efficiency of charge VS discharge is very high, like 95% or so. The thing I wonder about is this: If you have a battery that formerly took 90 minutes to charge fully, if you do it in one minute you are by definition going to need at least 90 times the current to do that job. That complicates the charging cycle for say, computers or cell phones and really complicates it for electric cars which already have something like a 25 kilowatt hour battery that say takes 8 hours to charge with house current.

    So to go from 8 hours, or 480 minutes, to one minute would mean the charge current would have to be about 500 times higher. Of course, only for one minute but still, 25 Kw/hr in 8 hours would take about 3 kilowatts continuous for 8 hours but to do it in one minute would require a power source capable of sourcing 1.5 MEGAwatts. That seems to me to be putting the charge system out of reach of a regular home owner, which would require having a system that could say, charge to 25 Kw in 8 hours but discharge it all in one minute? The only thing that could do that would be a supercapacitor, but I don't know of any with that kind of energy potential.

    You have any ideas about that?
  3. 06 Apr '15 20:01 / 3 edits
    Originally posted by sonhouse
    Usually the energy efficiency of charge VS discharge is very high, like 95% or so. The thing I wonder about is this: If you have a battery that formerly took 90 minutes to charge fully, if you do it in one minute you are by definition going to need at least 90 times the current to do that job. That complicates the charging cycle for say, computers or cell p ...[text shortened]... , but I don't know of any with that kind of energy potential.

    You have any ideas about that?
    capacitors and supercapacitors have far greater power density but, for now, supercapacitors have far lower energy density than a typical battery, surely too low for an electric car I think, but I don't know the theoretical upper limit of the energy density for supercapacitors so that might one day change.

    One way around the problem of the long recharge times for batteries is to simply have not one but two batteries for each car/devise; one for currently powering the devise and one currently unattached to the devise for being currently recharging. That way, all you have to do is simply occasionally swap the two batteries over; simple! I don't know why I don't see anyone ever talking about this, what seems to me, a pretty obvious idea. This might be too expensive to do with lithium batteries but I would guess it probably wouldn't be too expensive with these cheaper aluminum batteries.

    An electric car recharge station could work simply by replacing your partly discharged car-battery with a fully charged one (and the more energy is left in your old battery, the less you are charged for the fully recharged battery ) i.e. physically swap them around so there is no need to wait around for a car-battery recharge! And then your partly discharged car-battery could be slowly recharging at the electric car recharge station to make it ready for one of tomorrow's customers; simple! I find it pretty strange I have heard nobody else mention this idea. It is surely so simple that I think, surely, many other people have already thought of this!?
    It would, of course, require the electric car to be so designed so that swapping over the battery is a very quick and simple process and doesn't require undoing bolts etc.
  4. 06 Apr '15 20:57
    Originally posted by humy
    capacitors and supercapacitors have far greater power density but, for now, supercapacitors have far lower energy density than a typical battery, surely too low for an electric car I think, but I don't know the theoretical upper limit of the energy density for supercapacitors so that might one day change.

    One way around the problem of the long recharge times ...[text shortened]... pping over the battery is a very quick and simple process and doesn't require undoing bolts etc.
    "I find it pretty strange I have heard nobody else mention this idea. It is surely so simple that I think, surely, many other people have already thought of this!?"

    I read something like this tens of years ago in a popular science magazine. It's not at all a new idea.

    The thought was that you run into a small house, like a washing tunnel, were the battery is swapped automatically by a machine, you pay and drive away.

    I would be worried about the quality of the newly inserted battery pack. What guarantee do I have that the new one could give me a driving capacity to reach the destination as if it was a good one?

    If I could afford a Tesla car, I would buy one. Preferably a red. They sell quite good in Norway. Gives you an action radius of about 400 km in one go, if I remember correctly. Rechargable at home over night, and quickly recharged in 40 minutes for free on the McDonald parking lots.
    According
  5. Standard member sonhouse
    Fast and Curious
    06 Apr '15 22:13
    Originally posted by humy
    capacitors and supercapacitors have far greater power density but, for now, supercapacitors have far lower energy density than a typical battery, surely too low for an electric car I think, but I don't know the theoretical upper limit of the energy density for supercapacitors so that might one day change.

    One way around the problem of the long recharge times ...[text shortened]... pping over the battery is a very quick and simple process and doesn't require undoing bolts etc.
    But do you see what I mean when they tout fast charging batteries capable of being charged in one minute? One problem I see with that is what about heat generation? If you cram hundreds of amps into a battery that can accept such, wouldn't it tend to overheat?

    The double battery idea is not new, saw it in a science magazine a while back.
  6. 07 Apr '15 07:22
    Originally posted by sonhouse
    If you cram hundreds of amps into a battery that can accept such, wouldn't it tend to overheat?

    .
    Yes, I get your point. The battery may have to be extraordinarily energy efficient to not overheat if it is to be fully recharged in just one minute ( + too much load might be put on the local electric power supply )
  7. 07 Apr '15 08:36
    Originally posted by humy
    One way around the problem of the long recharge times for batteries is to simply have not one but two batteries for each car/devise; one for currently powering the devise and one currently unattached to the devise for being currently recharging. That way, all you have to do is simply occasionally swap the two batteries over; simple! I don't know why I don't see ...[text shortened]... s but I would guess it probably wouldn't be too expensive with these cheaper aluminum batteries.
    That is probably too expensive and complicated to do yourself in your own garage at home - at least with the lithium batteries which are a large part of the cost of an electric car.

    An electric car recharge station could work simply by replacing your partly discharged car-battery with a fully charged one (and the more energy is left in your old battery, the less you are charged for the fully recharged battery ) i.e. physically swap them around so there is no need to wait around for a car-battery recharge!
    This has been implemented in a number of electric car programs.
  8. 07 Apr '15 11:25 / 7 edits
    Originally posted by twhitehead

    This has been implemented in a number of electric car programs.
    I am relieved to hear that. I believe this is the best long-term solution to the battery recharge time problem.

    Anyone:

    is there a special technical name for this car-battery recharge solution?
    Or a special technical name for the more generic policy of keep swapping over rechargeable batteries in any devise like I described in this thread?
    I find it awkward to describe what it is I am referring to each time so I hope there is a special name for it.
    If there is not name for it, I will try and invent one assuming nobody here has any suggestions?
  9. Standard member sonhouse
    Fast and Curious
    07 Apr '15 12:03
    Originally posted by humy
    I am relieved to hear that. I believe this is the best long-term solution to the battery recharge time problem.

    Anyone:

    is there a special technical name for this car-battery recharge solution?
    Or a special technical name for the more generic policy of keep swapping over rechargeable batteries in any devise like I described in this thread?
    I find it a ...[text shortened]... If there is not name for it, I will try and invent one assuming nobody here has any suggestions?
    Battery pick up station comes to mind.
  10. 07 Apr '15 12:47
    Originally posted by humy
    I am relieved to hear that. I believe this is the best long-term solution to the battery recharge time problem.

    Anyone:

    is there a special technical name for this car-battery recharge solution?
    Or a special technical name for the more generic policy of keep swapping over rechargeable batteries in any devise like I described in this thread?
    I find it a ...[text shortened]... If there is not name for it, I will try and invent one assuming nobody here has any suggestions?
    One downside of this is that it requires that the batteries are easily and very
    quickly removable and re-fit-able to the car.

    This places constraints on the way the batteries are used and emplaced,
    possibly reducing the total battery size or increasing the reinforcing structure
    needed as the batteries cannot be in any way structural.
    In addition, busy battery hot-swapping stations would need to have on hand
    a very large number of large batteries, taking up lots of space, presenting a
    great fire risk [if Li-ion, other volatile] and this number gets even larger if all
    cars don't use the same size/shape battery... Can you see all car makers agreeing
    on one size/shape battery just for their own range of cars, let alone everyone else's?


    Also, as batteries are expensive, they are valuable.

    Being easy to remove introduces increased possibility of theft. [both from cars,
    and from the battery hot-swapping stations]

    These are by no means necessarily fatal concerns, but they could well mean that
    for any particular given car design/er it may well be more optimal to have batteries
    that are charged in-situ rather than hot-swapped. [perhaps this is the phrase you
    are looking for, battery hot-swapping stations?]
  11. 07 Apr '15 13:08 / 1 edit
    Originally posted by googlefudge
    One downside of this is that it requires that the batteries are easily and very
    quickly removable and re-fit-able to the car.

    This places constraints on the way the batteries are used and emplaced,
    possibly reducing the total battery size or increasing the reinforcing structure
    needed as the batteries cannot be in any way structural.
    [i]In addi ...[text shortened]... hot-swapped. [perhaps this is the phrase you
    are looking for, battery hot-swapping stations?]
    But the OP link suggests a solution: at a price of them having a lower energy density, aluminum batteries that are both a lot cheaper than lithium batteries and will not be a fire hazard. The obvious catch is the lower energy density but that might be acceptable.
  12. 07 Apr '15 13:11
    Originally posted by sonhouse
    Battery pick up station comes to mind.
    Yes, that is good. I am afraid the best my imagination has come up with so far is "battery swap scheme".
  13. 07 Apr '15 18:50
    Originally posted by humy
    Yes, that is good. I am afraid the best my imagination has come up with so far is "battery swap scheme".
    You didn't like "Battery Hot-Swapping Stations".
  14. 07 Apr '15 18:56
    Originally posted by humy
    But the OP link suggests a solution: at a price of them having a lower energy density, aluminum batteries that are both a lot cheaper than lithium batteries and will not be a fire hazard. The obvious catch is the lower energy density but that might be acceptable.
    The biggest problem is the one in italics

    "In addition, busy battery hot-swapping stations would need to have on hand
    a very large number of large batteries, taking up lots of space, presenting a
    great fire risk [if Li-ion, other volatile] and this number gets even larger if all
    cars don't use the same size/shape battery... Can you see all car makers agreeing
    on one size/shape battery just for their own range of cars, let alone everyone else's?"


    And making the batteries less energy dense only makes this problem worse,
    and making the batteries charge faster is an incentive to charge them in-situ and
    not hot-swap them.
  15. 07 Apr '15 19:11 / 1 edit
    Originally posted by googlefudge
    The biggest problem is the one in italics

    [i]"In addition, busy battery hot-swapping stations would need to have on hand
    a very large number of large batteries, taking up lots of space, presenting a
    great fire risk [if Li-ion, other volatile] and this number gets even larger if all
    cars don't use the same size/shape battery... Can you see all c ...[text shortened]... r m king the batteries charge faster is an incentive to charge them in-situ and
    not hot-swap them.
    sure, the lower energy density would mean they will take up more space and the stations would generally need more of them, but couldn't possible be a "great fire risk" if they are not lithium batteries but rather the fire-safe aluminum batteries and i don't see why the stations needing more of them would be an insolvable problem; just put the stations where there is plenty of room to put them somewhere such as in a big warehouse.