Become a fan of Slashdot on Facebook

 


Forgot your password?
Close
typodupeerror
×
Power Hardware

Battery Powered Tram Charges in 60 Seconds 176

Posted by ScuttleMonkey from the streetcar-named-yokubou dept.
SK writes to tell us that a new streetcar, powered by lithium battery, has been invented by the Railway Technical Research Institute in Kokubunji, Tokyo. The new transport is capable of speeds of 40 kph for 15 kilometers and can convert 70 percent of its deceleration energy into electricity which is then sent back to the battery which can recharge in under one minute.
This discussion has been archived. No new comments can be posted.

Battery Powered Tram Charges in 60 Seconds More

Battery Powered Tram Charges in 60 Seconds

Comments Filter:

  • Correct me if I'm wrong... (Score:5, Insightful)

    by Colin Smith ( 2679 ) on Monday October 29, 2007 @05:12PM (#21163025)
    But a tram runs on rails which mean it always follows a known route rather precisely and can therefore be supplied with electricity directly... No batteries required.

    Isn't this just solving a problem which doesn't really exist?
     

    • Re:Correct me if I'm wrong... (Score:5, Interesting)

      by WiglyWorm ( 1139035 ) on Monday October 29, 2007 @05:16PM (#21163081) Homepage
      Well, yes and no. Power delivery is not a problem at all. Look at the cable cars in San Fransisco, any modern subway... really most modern rail systems. However, if they can turn 70% of their breaking power in to electrical energy, accelerating the train back up to speed or, apparently, 15Km of crusing can be done absolutely for free. Lowering the carbon footprint to make it more environmentally friendly and cutting costs for the opperator all at once.

      • Re: (Score:2, Interesting)

        by Anonymous Coward
        Yup, and adding batteries and control electronics and employing people to write control software and building the damn things doesn't add any carbon at all!
        See, that's the problem with current thinking re the carbon problem. We're just throwing more technology at the problem, technology which is subsidized entirely by the present fossil fuel economy. The only real long term solution to the carbon footprint problem is to radically re-think how we live our lives. Do we need to travel to and from work everyday

        • Re: (Score:2, Interesting)

          by frup ( 998325 )
          Often the short term cost of a long term solution is great. From that the long term problem eventually gets solved/improved though. Even if this seems a waste in some ways it places building blocks for the next step. With out these kinds of projects it would be difficult for us to think differently or even transition to a new lifestyle. In New Zealand, if everyone employed solar water heating we would save 50% of household power usage from the old water cylinder. That's the amount a $1 billion power plant c

          • That's the amount a $1 billion power plant could give us extra. So each person spends an extra $10,000 on their home instead of a cheap water cylinder and the long term savings for the country are huge.
            Right... Because 1.4 million households spending $10,000 each to save a billion dollars makes perfect sense...

             

            • Re: (Score:2, Interesting)

              by frup ( 998325 )
              The benefit being a reduction in your personal power bill, lower carbon emissions etc. We did it and save around $100 per month now. Over 10 years your installation is free.
        • Agreed. Solution is simple. Convert all fossil fuel plants to nuclear and add more nuclear/solar (in desert areas, rooftops, for example) to generate hydrogen for stuff that is not fixed (eg. cars, trucks, long haul railway lines like in Siberia or Canada, etc.). Then you have no carbon footprint. Problem solved. Right?

          But until then, throwing money and technology by taxing carbon is probably the best way of dealing with CO2. CO2 is a waste and when consumers pay for the waste they generate (ie. business ge

        • Sure, all those things generate some pollution too. Question is: is that pollution greater smaller than that produced by feeding the tram for the duration of its service life? If so, then you have a victory, however minor it may be.

          Now, this of course does not in any way invalidate the argument that moving to a saner daily routine would help far more, but until then, this helps.

          • for the duration of its service life?
            One of the advantages of trams : in my town there are trams driving around that are 40 years(interiors get changed of course) old ...

        • Re:Correct me if I'm wrong... (Score:4, Funny)

          by SnowZero ( 92219 ) on Monday October 29, 2007 @11:20PM (#21166733)

          Do we need to travel to and from work everyday when all we do is manipulate information?
          No, for that job you live and work in the White House.

        • Re: (Score:2)

          by EatHam ( 597465 )

          Do we need to travel to and from work everyday when all we do is manipulate information?
          Yes, because there is a substantial set of the population that, when faced with the question of whether to manipulate information or manipulate other things based on the wide variety of porn at their fingertips, will choose to manipulate themselves.

          Which is not to say that there aren't plenty of people who just jerk off all day anyway.

      • Trams are the wrong solution (Score:5, Insightful)

        by Colin Smith ( 2679 ) on Monday October 29, 2007 @05:37PM (#21163371)

        However, if they can turn 70% of their breaking power in to electrical energy, accelerating the train back up to speed or, apparently, 15Km of crusing can be done absolutely for free.
        The problem with trams is the same problem any group transport vehicle has... But worse.

        Trams in particular have very short distances between stations, often only 500m or so. Great for getting on and off, it makes them very accessible unlike traditional rail which doesn't get used much because the stations are so far apart, but, because the distance is so short, they literally spend all of their time accelerating, decelerating and stopped.

        Now, the most efficient way to run a vehicle is at a constant speed, acceleration is expensive in terms of energy, and the more mass you have, the more energy you expend. Trams almost never reach a constant speed and because they're basically rail, they're extremely heavy as well.

        Essentially trams are a square peg beaten into a round hole. Hence the battery kludge to try to make them more efficient.

        • Re: (Score:3, Interesting)

          by b0s0z0ku ( 752509 )
          Now, the most efficient way to run a vehicle is at a constant speed, acceleration is expensive in terms of energy, and the more mass you have, the more energy you expend. Trams almost never reach a constant speed and because they're basically rail, they're extremely heavy as well.

          Rail doesn't necessarily mean heavy. And trams are usually powered by low-voltage DC (relatively low: 600V as opposed to up to 25kV for a lot of trains) overhead lines, which makes pumping energy from regenerative braking back i

          • Rail doesn't necessarily mean heavy.

            Meh. It pretty much does. It's the nature of the beast. If you're carrying a lot of people in a single vehicle, you need a vehicle which can carry the weight. Trams range from 20-50 tonnes per vehicle.

            e.g.
            http://www.edinburgh-tram.co.uk/tram.htm [edinburgh-tram.co.uk]
            http://www.railway-technology.com/projects/sheffield-tram/specs.html [railway-technology.com]

            Then you need an infrastructure which can handle the weight of the vehicles. This is usually also very expensive per mile.

            And keep in mind also that rolling friction on steel rails is a lot less than friction from a rubber tire on a roadway.

            Rolling resistance is secondary to air resistance and the effect on efficie

            • "Meh. It pretty much does. It's the nature of the beast. If you're carrying a lot of people in a single vehicle, you need a vehicle which can carry the weight. Trams range from 20-50 tonnes per vehicle."

              City busses aren't exactly light either.

              "Rolling resistance is secondary to air resistance and the effect on efficiency is much lower than simply going from internal combustion to electric."

              At lower speeds (under 25 mph/40km/h) rolling resistance has more of a pronounced effect. And that's where trams

              • City busses aren't exactly light either.

                10-15 tonnes per vehicle. I'm not saying trolley buses are a good solution either, being group transport vehicles. They're simply better than trams; they don't require $20-$40 million per mile infrastructure installed, they just need the overhead cables.

                At lower speeds (under 25 mph/40km/h) rolling resistance has more of a pronounced effect. And that's where trams spend most of their lives.

                The effect is the same, the proportion of the overall resistance is higher simply because air resistance is lower. It's still a small percentage compared to going from internal combustion to electric.

            • Re: (Score:3, Insightful)

              by Peeteriz ( 821290 )
              "stop/start that same train every 2 miles and it's a completely different story."

              But hey, that's the exact thing that this article is about! If this battery solution eliminates most (70%) of this overhead, then maybe it's not a completely different story anymore?

        • Re: (Score:2, Funny)

          by leenoble_uk ( 698539 )
          You just gave me an idea.
          How about instead of making the tram brake every time it reaches the station, the station is itself a rolling road (rail) which runs at a constant speed just below that of the tram, enabling peeople to comfortably get on and off at slower than walking speed, but the tram never stops and is always travelling at a constant speed. When the tram reaces the end of the station it finds itself travelling back at full speed.

          Hey I'm just an ideas man, you work out the technology and safety i

      • Always was this way. Batteries not included. (Score:5, Informative)

        by Ungrounded Lightning ( 62228 ) on Monday October 29, 2007 @07:09PM (#21164629) Journal
        Power delivery is not a problem at all. Look at the cable cars in San Fransisco, any modern subway... really most modern rail systems. However, if they can turn 70% of their breaking power in to electrical energy, accelerating the train back up to speed or, apparently, 15Km of crusing can be done absolutely for free.

        And it already works that way. And it has been working this way since brush-powered electric trains and buses were first built.

        If you've got a speed-controllable electric motor hooked to an electric grid, you can do regenerative braking by setting the motor's desired speed to something lower than its current speed. The motor then DEcelerates the vehicle, acting as a generator and putting the vehicle's energy (less resistive, eddy-current, hysteresis, and excitation losses) back into the power supply.

        If there are rotary converters (or suitably designed electronic converters) in the system (for instance: To turn line AC into DC or lower-frequency AC for the trains/buses), they do the same thing - pushing the energy back toward the main grid. If not, the energy is still usable by other vehicles on the system that happen to be consuming power, dropping the amount that needs to be pulled from the primary supply.

        This is very convenient: In addition to the energy savings, the vehicle's mechanical brakes get much less use, and much less wear. They can be reserved for the last moments of a full stop, holding the vehicle motionless when stopped, and for emergencies. This drastically reduces the necessary maintenance.

        What the super-fast-charge battery does is let you do the same thing - MAJOR regenerative braking - for a vehicle that's NOT continuously attached to a power grid. The current hybrids do some of this using more ordinary battery technology. But there are limits due to the batteries' slow charging, large losses, and weight. The fast charge means even a panic stop can be salvaged and a much lower weight of batteries is necessary for a given RATE of energy transfer.

        Also: The fast charge implies that the batteries lose very little energy when storing it (otherwise they'd melt down or catch fire). This implies low internal resistance, which also means fast and efficient DIScharge when you want the energy back. So we finally have batteries that can perform as well as (or better than) a (still mostly impractical) flywheel/motor-generator system for "peaking" storage. (TFA's stated losses of about 30% per stop/start cycle look about right for a system where the losses are virtually all in the motor and controller. That would be about 84% efficiency on both start and stop cycles, which is right in the ballpark for a good motor.)

        Size the batteries large enough to store the power of a vehicle coming down off about 8,500 feet of mountain freeway and making a full stop near sea level and you achieve the full potential of regenerative breaking: The engine then needs only to be big enough to fight friction - like under 20 horse - and can run at maximum efficiency when it runs at all. Size them maybe a tad larger to also run a couple long and hilly commute-and-shopping cycles on a line-powered charge without starting the engine - reserving the engine for long trips - and you also achieve a fully-functional "plug-in hybrid", a single vehicle adequate to completely replace a normal, non-hybrid, car in ALL service cycles and run off utility electricity (currently the equivalent of about $0.75/gallon gas) in all but cross-country trips.

        The usual statement about such breakthroughs - that deployment is always 10 years away - seems to have been hurdled. This technology was at that stage a year or two back. But THIS announcement, of deployment in a vehicle (even though experimental) implies it's not just sitting in the lab, but getting some real-world production and testing. Once that's a production vehicle (if not sooner) the batteries will also be available to automobile designers...
        • So we finally have batteries that can perform as well as (or better than) a (still mostly impractical) flywheel/motor-generator system for "peaking" storage. (TFA's stated losses of about 30% per stop/start cycle look about right for a system where the losses are virtually all in the motor and controller. That would be about 84% efficiency on both start and stop cycles, which is right in the ballpark for a good motor.)

          Make that definitely "better than" flywheel peaking.

          A flywheel peaking system runs the pow
      • Not that I disagree with your point, but cable cars in San Francisco aren't electric. The "cables" in the name are looped steel cables run under the road. The trains travel by clamping onto these cables and "riding" them, the way you might grip to rope to get pulled up a ski hill. Next time you're crossing the street in San Fran, look down and you can see the cable whizzing by under the street.

    • Re: (Score:3, Insightful)

      by 7macaw ( 933316 )
      "Conventional" tram needs wires along the whole route, while this one would need only a few recharging points => less wires needed.

      I suppose a bus that works in the same fashion could be even more beneficial since it would combine the route flexibility of a bus with the cheapness and cleanness of an electrically-powered vehicle
      • You're reply is pretty much spot on - having a battery will reduce the amount of wires needed. You're also correct in pointing out this would be even better for a bus - note that some work was being done in the 1960's on flywheel powered buses with recharging stations at the bus stops.
      • And no $20million/mile rails required...
         

        • Re: (Score:2)

          by thogard ( 43403 )
          The overhead lines for straight lines aren't the problem. Its the lines over stations, turnouts and intersections and bridges that are the real problem.

          The train and tram system in Melbourne use different power (AC/DC and different voltages) and there are places where the trams cross the train lines and there is a bit of fancy insulation going there and they need to maintain speed or else they stop.

      • Re: (Score:3, Insightful)

        by fm6 ( 162816 )
        One problem with buses is that they require a lot more power than railed vehicles. I would guess that this new technology provides enough energy for a tram (in the U.S. we call them "light rail" or "trolleys") but not enough for a bus. But I'm no expert.

        • I would guess that this new technology provides enough energy for a tram (in the U.S. we call them "light rail" or "trolleys") but not enough for a bus.

          Actually, as indicated earlier, they've been testing systems in New York City [greencarcongress.com] using another regenerative braking system called HybriDrive from these folks... [baesystems.com]

          No idea if the BAE system has the "70%" conversion rate of this one or not.

        • Re: (Score:2)

          by thogard ( 43403 )
          Busses tend to weigh much less than trams since trams tend to be built like rail cars by companies that deal with rail roads. Trams could be much lighter but they aren't mostly because of a hundred years of doing things the same way. The new ones they just bought for Melbourne Australia are heavier and use more energy per passenger than the last ones and their energy requirement per passenger is still higher than high efficiency cars. Here in Melbourne one ticket will let your ride busses, trains or tram
    • Since it can recharge from itself, it uses less energy, and therefore doesn't cost as much to keep going.

      PS: The self-recharging tram is not in charge of Gundam.

    • But a tram runs on rails which mean it always follows a known route rather precisely and can therefore be supplied with electricity directly... No batteries required.

      Currently, many tram systems (for example, Melbourne, Berlin) do generate electricity when braking, giving back electricity to the tram network and helping to save some energy, if another tram happens to be accelerating or running at the time.

      However, if a tram is on a regional route and far from any other trams, such as at a late hour, this energy is wasted.

      Using flywheels and other mechanical devices has been tried but is dangerous and expensive.

      This battery device would greatly increase the efficien

    • "Isn't this just solving a problem which doesn't really exist?"

      No, it isn't. Consider this: This technology could be applied to buses (is in some ways, if one considers non-gasoline/non-diesel buses) and free the pole-powered buses of delays causes when the bus ahead (or, the trolley car on tracks using a different power line but is somehow obstructing the bus' run) breaks down or, (in the case of SF MUNI) when some passenger threatens or harasses the driver, who then says (after a few warnings-- especially

  • Sweet!! (Score:2, Funny)

    by iknownuttin ( 1099999 )
    he institute will start conducting test runs in Sapporo at the end of November to check the streetcar's capacity.

    A street car that runs on Sapporo! Can you drink out of the tank! Oooo sushi bar in the back of the car, drink out of the tank, party train!

    Wait, it's 'in' not 'on'?!?

    Dammit! I just bought plane tickets. Shit.

  • Obviously... (Score:5, Funny)

    by locokamil ( 850008 ) on Monday October 29, 2007 @05:18PM (#21163117) Homepage
    ... Sony will be lead supplier for the lithium ion batteries to power the vehicles, thus affording the industrial conglomerate an excellent opportunity to diversify into the burgeoning mass-traffic-explosion industry.

    • Re: (Score:2)

      by Trogre ( 513942 )
      I'm looking forward to the REVA coming to my country, the newer versions of which come with Li-Ion batteries. No more explosive than dead dinos.

    • Think of it as a sort of hybrid... If the electric power fails, you can just fall right back on good old internal combustion.

  • How much charge? (Score:4, Interesting)

    by mangu ( 126918 ) on Monday October 29, 2007 @05:23PM (#21163189)
    "Recharge in under one minute". Sure, but how much charge? Take how many kilowatt-hours of charge you want, multiply it by 60 and you'll get how many kilowatts of power you need to charge it in a minute. Now divide by the voltage to get the current. How big would the cable and the contacts need to be?


    It seems we now have the ideal battery (also called a "capacitor"), now let's concentrate on creating the superconducting cables and contacts.

    • A quick Google search turned up the rough conservative estimate of one square millimeter of copper bus bar per 10 amperes of current.
    • A normal subway system might have DC power delivered at the third rail at either
      600 Volts or 750 Volts. It can provide several thousand amps (6000 Amp IIRC).
      So using the lower voltage figure, thats 3600 KW.

      I think third rails are about 5 inches by 5 inches.

      You should see what a CRT monitor looks like 50 feet away from third rails
      when a train approaches.
  • TFA:

    According to the institute, it uses about 10 percent less power than existing streetcars.

    Apparently, not very. Consider the initial cost of the battery (li-ion is not cheap, the tesla roadster [wikipedia.org] for example costs $100,000 most of which is for the battery pack, ~ $75,000 IIRC). Then consider the cost of disposing or recycling the batteries which will presumably need to be done several times in the life of the streetcar. I guess this is a start, but at 10% less power, I don't see this as much of an advantage.

    • Re: (Score:2)

      by repvik ( 96666 )
      Li-ION is worthless for this purpose. It'll only last a few hundred charge/discharge cycles. Lead-acid batteries are both cheaper and longer lasting.

      • Re: (Score:2)

        by vivian ( 156520 )
        Who said anything about using standard Ii-Ion batteries? TFA just says they are using Lithium batteries. I would imagine they are using LiFePO4 batteries (Lithium phosphate batteries) as have already been covered on slashdot several times before. The nano particle versions of these have charge characteristics similar to what are described in the article, have much longer duty cycles than lead acid batteries, much better power to weight rations and capacity, and have significantly improved safety over standa

  • Streetcar (Score:5, Funny)

    by HTH NE1 ( 675604 ) on Monday October 29, 2007 @05:26PM (#21163245)

    a new streetcar, powered by lithium battery, has been invented by the Railway Technical Research Institute in Kokubunji, Tokyo. The new transport is capable of speeds of 40 kph for 15 kilometers and can convert 70 percent of its deceleration energy into electricity which is then sent back to the battery which can recharge in under one minute.
    I desire this streetcar.
  • gone in 60 second !
  • Wow, charging the batteries in one minute? I'm not sure about lithium batteries, but standard lead acid batteries have a recommended maximum charge rate. For them to recharge the battery in one minute, they're going to have to be pushing a LOT of current...especially considering they're going 15km on one charge. I'd be worried about battery life on these (probably) expensive batteries.
  • Battery operated streetcars are nothing new - see The Time of the Trolley by William D. Middleton. Battery cars were used in such diverse places as New York City and Billings, Montana.


    What makes this new is improvements in motor control circuitry making regeneration a lot more practical for streetcar use and improvements in battery technology - the old battery cars typically used Edison cells.

  • Charge a lithium battery in one minute? (Score:3, Funny)

    by ScrewMaster ( 602015 ) on Monday October 29, 2007 @05:43PM (#21163471)
    Huh ... I didn't realize that Japan was getting back into explosives research.

  • hopefully this time they will stay around (Score:5, Interesting)

    by DMoylan ( 65079 ) on Monday October 29, 2007 @05:48PM (#21163555)

    The original Drumm train was constructed in the Great Southern Railways workshops at Inchicore. The weight of the train with passengers was about 85 tons. There was seating accommodation for 140 passengers. The train could accelerate from standstill at about 1 m.p.h. per second and attain speeds of 40 to 50 m.p.h. with ease. The train was fitted with a successful system of regenerative braking, whereby an important fraction of the energy surge made available on a down-gradient or on de-accelerating at a station was returned to the battery. The Drumm Battery train operated successfully on the Dublin to Bray section of the line with occasional runs to Greystones some five miles farther on, from 1932 to 1948. As passsenger numbers increased two pairs of power units were joined under the control of one driver and later a specially wired coach was put between the two trains bringing its capacity up to 400 passengers. By 1939, four Drumm trains had been built but it became impossible to secure orders and raw material once the World War 11, 1939-1945, broke out. The Drumm Battery Company folded in 1940. The outbreak of the war made the Drumm trains invaluable as coal for steam engines was in short supply and inferior. With the war over, it was decided in 1949 to scrap the Drumm trains at a time when the promise of diesel locomotives pointed to the end of the steam era. The Drumm trains, minus their batteries were sometimes used as ordinary coaches.
    http://chem.ch.huji.ac.il/history/drumm.html [huji.ac.il]
    • World War Eleven you say? I know the Irish stayed Neutral officially for WW2, but WW11? Yeesh.

      • Why am I always the last to find out about these things? First it's a club meeting here I somehow did not know about but everyone else did, then something else there, and finally now I hear that 9 World Wars happened when I wasn't looking. I know I occasionally miss things, but this is just too much!

        And more importantly, who won them?

  • Awesome Lithium Tech (Score:4, Interesting)

    by Bryan Ischo ( 893 ) on Monday October 29, 2007 @06:41PM (#21164253) Homepage
    If its battery is anything like lithium ion batteries used in laptops, then after a year it'll only go 5 km on a charge instead of 15. Also it will do weird things like indicate that it has enough charge to go another 5 km but just suddenly use up its last 20% in under a minute.

    I am not a big fan of lithium ion tech. It seems very gimmicky to me; allowing manufacturers to claim that their laptop batteries last N hours when in fact that will only be true for less than 6 months, as the charge capacity of lithium ion batteries always rapidly deteriorate.

    My Panasonic Y2 battery started at 6+ hours per charge, and is now, after not even three years, down to about 2.5 hours per charge.

    So if the streetcar in question uses similar tech, then I would expect its range to diminish rapidly with recharges. Since it will be recharged much more frequently than any laptop would, can we even expect its battery to last a whole year before becoming basically worthless?
  • First, well, I'm no expert in fast charging, but when I fast charge batteries, they tend to get quite warm. Isn't a lot of energy wasted in heat when you press the juice in?

    And second, in what way is that superior to an overhead power line to draw the power from? I mean, train lines are kinda set in stone (or rail, rather), so it's not like cars that need to be able to drive where they want to.
    • Overhead lines are by definition signifigantly longer than the distance from the motor to the batteries within the vehicle, so you have transmission loss. So if you do regenerative braking and dump the power into overhead lines, you lose a couple of percent dumping the power in, and a couple more percent taking it back out, just from transmission line loss.

      On the other hand, current battery technology is fairly heavy, so you're losing some of the value by accelerating and decelerating the batteries thems

  • ... what kind of fireball a giant lithium battery would create (?) Of course this is a minor detail as the power cell could be based on any storage technology conceivably.

    I have a feeling that increasing speed is the biggest issue facing this technology because, if I'm not mistaken, most ground vehicles expend most of their energy defeating wind resistance. Thus if most energy were spent defeating wind, it would be impossible to reclaim most of that energy during deceleration. IANA fluid dynamics expert,
  • That's about how long the driver takes to argue with some hobo about dodging the fare. They could recharge at almost every stop!
    • that's not common in japan's train system, events with periodicity of one minute would be groping of female passengers by perverts (aka japanese businessmen)

  • Interesting application (Score:3, Interesting)

    by PPH ( 736903 ) on Monday October 29, 2007 @08:07PM (#21165217)
    Besides regenerative braking, the battery technology could be used in areas where it is expensive, or unsightly to install an overhead conductor. The trolley can charge off the distribution system and then continue along routes where no overhead is required.

    Visit Seattle and ride the SLUT [nwsource.com]!

  • I don't understand why it takes so long to charge batteries. Why can't the charger charge little chunks of the battery independently, in parallel, then discharge the bank of batteries serially? Why not break down the bank into the maximum number of little chargeable batteries, for the fastest charging time? There might be some inefficiencies in the discharge through several separate batteries, but the slow recharge is the main obstacle to forgetting these batteries are even part of the problem.

    • I don't understand why it takes so long to charge batteries. Why can't the charger charge little chunks of the battery independently, in parallel, then discharge the bank of batteries serially? Why not break down the bank into the maximum number of little chargeable batteries, for the fastest charging time? There might be some inefficiencies in the discharge through several separate batteries, but the slow recharge is the main obstacle to forgetting these batteries are even part of the problem.

      The big rea

      • But the idea is that you don't just put 3A @4.2v into 2 cells in parallel instead of 1A @12.6V into 3 cells in series. The point is that you put 9A @ 4.2V into 3 in parallel, 3A @ 4.2V each.

        Then discharge them in series to sum their output voltage.

        Why not use the same power that currently charges a single large battery 3x as long instead to charge a battery 3x as small? That would be faster than charging the big battery with it, right? And do that to 3 different small batteries at the same time, which are t

        • Re: (Score:2)

          by aXis100 ( 690904 )
          You miss the point. The limitation is not the available source power - it's how much current (and thus heat) each cell can handle based on it's design.

          Breaking a cell down into smaller chunks decreases the electrode surface area, reducing the current handling capability. Even though this might get partially offset by the increased cooling surface area, I'd think there would be litle nett benefit.
          • Well, if the limit is the electrode surface area, then why not make electrodes in elaborate thin lattices, like metal snowflakes, or concentric cylinders drilled with lasers, coated with the rechargable cell chemicals?

            • Well, if the limit is the electrode surface area, then why not make electrodes in elaborate thin lattices, like metal snowflakes, or concentric cylinders drilled with lasers, coated with the rechargable cell chemicals?

              You also have to worry about the resistance in the electrolyte, and the contact between the electrodes and the chemicals. While I'm sure they do optimise the surface area, I'm not sure it is as simple as "larger = better". I imagine you have to start taking into consideration how rapidly vario

  • A lot of questions about the why (Score:4, Informative)

    by SmallFurryCreature ( 593017 ) on Tuesday October 30, 2007 @06:16AM (#21168563) Journal

    Almost all trains are electrical nowadays, where they get their power from is the big question. Diesels get it from carrying a diesel generator with them. Handy because you can be totally disconnected from the net, disadvantage, extra weight (not that much of a problem in cargo trains where the locomotive needs all the weight it can get) and you are limited by the amount of fuel you can carry. Plus you smell bad.

    The brits get their power from a third rail. Very hard wearing BUT you got a live wire exposed where everyone can touch it. Bad for level crossings, meaning the train needs facilities to be able to cross a spot without third rail.

    Most other trains including light rail system like in the article and trolly busses, use an overhead wire (busses need two since they can't use the rails as the second wire). The problem with this is that it is fairly expensive, can easily break and gets in the way at level crossings where it puts a height restriction on traffic using the crossing.

    There are ways around this, for instance at a bridge in holland by zaandam the overhead wire just has a missing part. Since trains typically only got one pentograph the train better be at speed or it will find itself without power (it is only a few meters and trains are notknown for their short stopping distances so this happening is highly unlikely).

    This tram would allow itself to run off the overhead wires where they can be installed, but continue normal operation where they can't. This would make planning a lot easier because you can then keep roads open for special transports and still have tram system. This is extremely handy as lifting the wires everytime something big needs to pass is a hassle.

    Finally why trams and not busses.

    Several reasons, the simplest is driving license. Buss requires a bigger more expensive license then a tram/metro. This is important because while their not all that many jobs for a tram/metro driver, trucking has plenty of competition.

    Trains offer a lot more space, because they can be build differently. A buss of the same weight as a tram simply can carry fewer people. While I have seen segmented busses with three segments now, that can carry a lot of people, they are still of lesser capacity then trams and have lost a lot of the freedom of movement of small busses.

    Basically trams can move more people then busses can, on less real estate. The prime example might be in holland, between Leidseplein and Koningsplein, where trams run in both directions but the tracks "merge" in the street and split again on the bridges. If you know the area, imagine implementing the same amount of transportation with busses. YIKES!

    Busses have their use, on infrequent routes, or routes that are too complex for a tramline. But when you have to move lots of people at street level, trams make a lot of sense.

  • That device charges so fast, that I'm not sure that it is a chemical battery. I suspect that it is a super capacitor, which stores energy as an electrical charge.

Slashdot Top Deals

The 11 is for people with the pride of a 10 and the pocketbook of an 8. -- R.B. Greenberg [referring to PDPs?]

Close