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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / December 2006efficiency of regenerative braking?
What is the efficiency of regenerative braking in electric vehicles? How much kinetic energy is recovered? -- Rich | What is the efficiency of regenerative braking in electric | vehicles? High. How much kinetic energy is recovered? Almost all. Losses are in heating only, brakes heat a lot, cables, motors and batteries very little. > | What is the efficiency of regenerative braking in electric > | vehicles? > High. Isn't regenerative braking just the DC traction motors running backwards? An alternator that worked over a broad rpm range touted 70% efficiency in a recent patent. It would be interesting if they could beat that. Bret Cahill > > | What is the efficiency of regenerative braking in electric > > | vehicles? [quoted text clipped - 3 lines] > Isn't regenerative braking just the DC traction motors running > backwards? No. Graham > > > | What is the efficiency of regenerative braking in electric > > > | vehicles? [quoted text clipped - 5 lines] > > No. How is the electricity being regenerated? By another component, say, an alternator or DC generator mounted on the same shaft as the traction motor? Alternators generally aren't all that efficient off the design point rpm. Bret Cahill > > > > | What is the efficiency of regenerative braking in electric > > > > | vehicles? [quoted text clipped - 9 lines] > an alternator or DC generator mounted on the same shaft as the traction > motor? It's called motor-generator action. > Alternators generally aren't all that efficient off the design point rpm. Traction motors aren't alternators. What gave you that idea about the rpm anyway ? Graham > What gave you that idea about the rpm anyway? You know how to brake at just one rpm? Bret Cahill > > What gave you that idea about the rpm anyway? > > You know how to brake at just one rpm? What *are* you talking about ? Have you gone mad ? Graham > > > What gave you that idea about the rpm anyway? > > You know how to brake at just one rpm? > What *are* you talking about ? By definition, braking takes places over a wide range of rpms. But generators and alternators ain't so efficient over a wide range of rpms. What's the solution? Bret Cahill |> > > What gave you that idea about the rpm anyway? | [quoted text clipped - 8 lines] | | What's the solution? Same as your car. Use the handbrake, idiot. > |> > > What gave you that idea about the rpm anyway? > | [quoted text clipped - 10 lines] > > Same as your car. Use the handbrake, idiot. You'll need friction braking in addition to dynamic braking for rapid braking anyway. Hence it can also be used to bring a vehicle to a stop. Graham > > > > What gave you that idea about the rpm anyway? > [quoted text clipped - 6 lines] > But generators and alternators ain't so efficient over a wide range of > rpms. Aren't they ? > What's the solution? To work with what you've got and make the best of it. Graham > > > > What gave you that idea about the rpm anyway? > [quoted text clipped - 8 lines] > > What's the solution? Replace the RPM's with RPS's. Since the only cranks who even use RPMs is GM & Asswipes Inc, > Bret Cahill |> What gave you that idea about the rpm anyway? | | You know how to brake at just one rpm? You know how much current it takes to accelerate a train to just one rpm, clueless fuckhead? >|> What gave you that idea about the rpm anyway? >| >| You know how to brake at just one rpm? > >You know how much current it takes to accelerate a train to just >one rpm, clueless fuckhead? It would depend. Do Brit trains spin on their long axis, or end-over-end?  SignatureBill Snyder [This space unintentionally left blank.] > |> What gave you that idea about the rpm anyway? > | > | You know how to brake at just one rpm? > > You know how much current it takes to accelerate a train to just > one rpm, clueless fuckhead? ------------------ it i s not only for trains it is as well or mostly for cars !! (they are the great energy wasters and poluters !! Y.P ----------------------------------------- > Isn't regenerative braking just the DC traction motors running > backwards? Simply put, yes. In the current hybrid system common to several manufactures, there are two motors in the transaxle. The larger motor is designated for providing the majority of motive torque. The smaller motor is used as a "starter" as it is attached directly to the engine output, and also functions to react to the larger motor to effectively create infinitely variable output gearing ("shifting"). To get to the point, both motors are either energized or tapped by the HV ECU to create torque or recharge the HV battery, respectively. The motors don't run "backwards" but are used in reverse current flow to charge the HV battery via an ac/dc converter that is managed by the HV ECU. Regeneration occurs whenever the various ECUs communicate to the HV ECU that charging is the correct strategy, be it during braking, extended battery-only operation, startup, or whatever else I'm forgetting. Toyota MDT in MO > > Isn't regenerative braking just the DC traction motors running > > backwards? > Simply put, yes. In the current hybrid system common to several > manufactures, there are two motors in the transaxle. The larger motor [quoted text clipped - 4 lines] > point, both motors are either energized or tapped by the HV ECU to > create torque or recharge the HV battery, respectively. What's the efficiency of the motor-generator in generator mode? Is it the same at any rpm? Bret Cahill > What's the efficiency of the motor-generator in generator mode? Probably in the same region as its efficiency as a motor but I have to say I'm not totally sure. > Is it the same at any rpm? The same principle applies. Graham |> > Isn't regenerative braking just the DC traction motors running | > > backwards? [quoted text clipped - 11 lines] | | Is it the same at any rpm? Are you an engineer, stupid f.ck? > > | What is the efficiency of regenerative braking in electric > > | vehicles? [quoted text clipped - 10 lines] > > Bret Cahill As others here have pointed out, the motors don't run backwards, the electrical current does. When DC electric motors run they also act as generators. The voltage produced by the generator, sometimes called the "back EMF" is proportional to the rpm. As the rpm goes up this back EMF goes up and limits how high the rpm will go with no load on the motor. One way to make the motor charge the battery is to use a motor with field windings and control the back EMF by controling the field current. This same idea is used for the "voltage regulator" in many automotive alternators. Actually I think the most efficient systems in use today are varialbe frequency AC systems. Many of the same ideas work and some are easier to impliment with AC rather than DC. Bruce > > > | What is the efficiency of regenerative braking in electric > > > | vehicles? [quoted text clipped - 26 lines] > frequency AC systems. Many of the same ideas work and some are easier > to impliment with AC rather than DC. No they don't. Varible Frequency networks are usually called servo motors, Which are as often as not these days, being replaced the computers, rather than electrical systems. Wide area power distriubtion genarators don't even work unless you have them synchronised to about 60Hz +/- 0.1 Hz, > Bruce > > > > | What is the efficiency of regenerative braking in electric > > > > | vehicles? [quoted text clipped - 34 lines] > don't even work unless you have them synchronised > to about 60Hz +/- 0.1 Hz, We weren't talking about networks, we were talking about motors and controllers. There are controllers that can convert the DC from batteries info AC and vary the frequency to control the motor's RPM. For industrial use on grid power the controller converts the 60 Hz input to whatever frequency it needs. Bruce > > > > > | What is the efficiency of regenerative braking in electric > > > > > | vehicles? [quoted text clipped - 37 lines] > We weren't talking about networks, we were talking about motors and > controllers. Just by saying "motors and controllers" means you're tallking about a network, It's just a local separable network. There are controllers that can convert the DC from > batteries info AC and vary the frequency to control the motor's RPM. That's only because DC is not a voltage, it's a capacitance. > For industrial use on grid power the controller converts the 60 Hz > input to whatever frequency it needs. It's unlikely it can it convert to 100 GHz, since that's the frequency band weather balloons use, > Bruce > > There are controllers that can convert the DC from > > batteries info AC and vary the frequency to control the motor's RPM. > > That's only because DC is not a voltage, it's a capacitance. Do you always talk sh.t ? Graham > > > There are controllers that can convert the DC from > > > batteries info AC and vary the frequency to control the motor's RPM. > > > > That's only because DC is not a voltage, it's a capacitance. > > Do you always talk sh.t ? Well it's invariant in sci.energy. Since Bill Clinton moderates the norron group, and sci.chem funds it with kickbacks to the Neo Commie coommittee for the promotion of reverse osmosis and sychronicity.. > Graham > > > > There are controllers that can convert the DC from > > > > batteries info AC and vary the frequency to control the motor's RPM. [quoted text clipped - 8 lines] > the Neo Commie coommittee for the > promotion of reverse osmosis and sychronicity.. Fine. You're an insane k00k. No problem. Graham > > > > > There are controllers that can convert the DC from > > > > > batteries info AC and vary the frequency to control the motor's RPM. [quoted text clipped - 10 lines] > > Fine. You're an insane k00k. And you're a Buckeyball wannabee moron who should really post to alt,sci.clinton rather than a newsgroup. > No problem. > > Graham > > > > > > There are controllers that can convert the DC from > > > > > > batteries info AC and vary the frequency to control the motor's RPM. [quoted text clipped - 13 lines] > And you're a Buckeyball wannabee moron who should really > post to alt,sci.clinton rather than a newsgroup. You're a clueless insane k00k. Graham > > > > > > > There are controllers that can convert the DC from > > > > > > > batteries info AC and vary the frequency to control the motor's RPM. [quoted text clipped - 15 lines] > > You're a clueless insane k00k. You're a f.cking ozone-depleted retard who should practice butthole surfing with Mao's Tomb. Since Clinton only hires Massad morons. and Bush is too coked-up to find his way to the Humvee Shop. > Graham > What is the efficiency of regenerative braking in electric > vehicles? How much kinetic energy is recovered? According to Wikipedia, it's just a bit over 30%. http://en.wikipedia.org/wiki/Regenerative_braking Some other sources appear to quote higher values, but I think the figures you find will depend on whether you're looking solely at the efficiency of the motor during regenerative braking, the amount of energy that ends up the batteries, or the amount of *recoverable* energy that ends up in the batteries -- the figures for each will all be different. It isn't clear to me which the Wikipedia article refers to. > > What is the efficiency of regenerative braking in electric > > vehicles? How much kinetic energy is recovered? ============================================= Lets say you have a 20 HP/15KW EV with a 144V battery pack cruising at 50% pwm. The motor would have about 72V applied and we can assume if the controller was disconnected and the generated voltage read while coasting, it might be 50 or 60V... certainly less than the applied voltage and less than the battery stack. If you just attach this to a cap bank, it will be like 'shorting' the armature, so the braking effect will be whatever torque the motor puts out at that V and I. I thought you could control this braking effect by putting a bike pedal toe cup on the accelerator and pulling back on the accelerator to control the regen pwm 0-100%. Of course, the braking effect decreases as the motor and car slows and as the cap bank charges. After braking, an dc to dc step up can charge pump the braking capture caps up to 144+V to go back in the batteries. My main question remains.... if the motor is generating 70V, should the caps in the regen capture bank have the same voltage rating? > > What is the efficiency of regenerative braking in electric > > vehicles? How much kinetic energy is recovered? [quoted text clipped - 9 lines] > that ends up in the batteries -- the figures for each will all be > different. It isn't clear to me which the Wikipedia article refers to. The answer depends on the details of the specific application. Figure the motor/generator itself is 90% to 95% efficient. That would mean that you would lose 5 to 10% putting the energy into storage, then another 5 to 10% converting it back to mechanical energy. If the battery pack is used to store the energy, it has internal resistance so some of the energy is lost as heat. Batteries are not very efficient for rapid charge and discharge cycles. As a guess let's say you get 60% of what you put in back out, with the remainder going to heat. So you could be looking at 90%*90%*60%=48.6% >From that you could subtract maybe another 10% for loses in the controler, bringing it down to just under 40%. There could be a bit more lost if a DC to DC voltage converter is used. Using capacitors eliminates the battery losses, but they mean added complexity, cost and weight. My guestimate would be that a good capacitor system should be able to recover 70%, a good battery system 50% and any decent system at least 30%. Something to keep in mind is the energy of a moving vehicle is proportional to the square of its velocity. So a car doing 30 mph with a 50% recovery system could get back up to about 21 mph on the recovered energy. Shows how it can make a big difference in stop and go city driving. Bruce >> > What is the efficiency of regenerative braking in electric >> > vehicles? How much kinetic energy is recovered? [quoted text clipped - 36 lines] >a 50% recovery system could get back up to about 21 mph on the >recovered energy. Well, you should keep in mind that the amount of kinetic energy present at any moment is a very small fraction of the amount of energy used overall. If you take a car with a mass of 1000kg going at 15m/s (about right for city driving) its kinetic energy is a tad over 110 kJ, the equivalent of 2.5g of gas. That's thermal, of course, factoring in efficiencies it may be the equivalent of 7-8g of gas (in terms of delivered mechanical energy). And now you recoup about 30% of this. Unless you spend all your driving accelerating like hell from the light, then slamming on the breaks before next light, I doubt you'll ever recoup more than a small fraction of what the system costs. But, it makes a good selling point:-) > Shows how it can make a big difference in stop and >go city driving. Some difference, hardly big. Mati Meron | "When you argue with a fool, meron@cars.uchicago.edu | chances are he is doing just the same" > Figure the motor/generator itself is 90% to 95% efficient. Is it 90 - 95% efficient acting as a DC generator over a broad range of rpms? Bret Cahill |> Figure the motor/generator itself is 90% to 95% efficient. | | Is it 90 - 95% efficient acting as a DC generator over a broad range of | rpms? Do you know what a stepper motor is, sh.t-for-brains? > |> Figure the motor/generator itself is 90% to 95% efficient. > | > | Is it 90 - 95% efficient acting as a DC generator over a broad range of > | rpms? > > Do you know what a stepper motor is, sh.t-for-brains? It is a motor where the armature can be rotated in small increments or steps. Really doesn't have much to do with what we are talking about. In answer to Bret's question, yes, the efficiency is over a fairly wide range. It goes down under heavy loads at low rpm because high currents are needed to produce high torque, and resistance losses are proportional to the square of the current. That is why it is best to use a transmission even though an electric motor can work without one. | > |> Figure the motor/generator itself is 90% to 95% efficient. | > | [quoted text clipped - 5 lines] | It is a motor where the armature can be rotated in small increments or | steps. Really doesn't have much to do with what we are talking about. Stepper motors I've used can stop on a dime. Try loading the National grid with one by reversing it. This is really very simple, all you do is try to drive in reverse. I've hooked up an ordinary 3-phase squirrel cage motor to an old Rolls Royce engine out of a scrapped Vanden Plas, connected the supply and started the engine. Bingo, the supply meter ran backward. Fuel was natural gas, heat was used to warm the workshop, a water jacket around the exhaust pipe. | In answer to Bret's question, yes, the efficiency is over a fairly wide | range. It goes down under heavy loads at low rpm because high currents | are needed to produce high torque, In either direction. | and resistance losses are | proportional to the square of the current. That is why it is best to | use a transmission even though an electric motor can work without one. Nothing wrong with gearing, I agree. You need that to accelerate rapidly, so it will for deceleration too. Cahill is not an engineer, he's an idiot troll pumping out one-liner questions to be antagonistic and argumentative. If you have one train approaching a station and another stationary, couple them electrically without external supply then the approaching train will slow as the stationary train accelerates, simply energy transfer. Dynamic braking I've used on AC electric motors by shorting out the windings. They stop as fast as they start. > | > |> Figure the motor/generator itself is 90% to 95% efficient. > | > | [quoted text clipped - 14 lines] > backward. Fuel was natural gas, heat was used to warm the workshop, > a water jacket around the exhaust pipe. Stepper motors are normally used to position things, like the slide on a machine tool. A single revolution may be broken down into 3600 steps. The motor can be made to stop at any of the positions and resist being pushed from that position. When used to turn a screw that can translate into positioning to .00001 inches. With most drive motors they don't worry so much about the position as the rpm. > | In answer to Bret's question, yes, the efficiency is over a fairly wide > | range. It goes down under heavy loads at low rpm because high currents > | are needed to produce high torque, > > In either direction. Yes, and when stopped they use energy to hold a position. So you are best off to use a friction brake to hold a position once stopped. They don't wear out that way anyway. > | and resistance losses are > | proportional to the square of the current. That is why it is best to [quoted text clipped - 9 lines] > Dynamic braking I've used on AC electric motors by shorting out the > windings. They stop as fast as they start. Yes, but the energy is wasted as heat that way. Better than wearing out brake pads but not as good as feeding power back in to the grid and turning the meter backwards. | > | > |> Figure the motor/generator itself is 90% to 95% efficient. | > | > | [quoted text clipped - 21 lines] | can translate into positioning to .00001 inches. With most drive | motors they don't worry so much about the position as the rpm. You mean like this: http://www.americanrobot.com/main.html | > | In answer to Bret's question, yes, the efficiency is over a fairly wide | > | range. It goes down under heavy loads at low rpm because high currents [quoted text clipped - 5 lines] | best off to use a friction brake to hold a position once stopped. They | don't wear out that way anyway. No problem using a friction brake. | > | and resistance losses are | > | proportional to the square of the current. That is why it is best to [quoted text clipped - 13 lines] | out brake pads but not as good as feeding power back in to the grid and | turning the meter backwards. Exactly. Just not practical for the application I was working on. What IS practical is starting and stopping trains, and what is even more practical is a computer controlled subway system, and what is even more practical than that is a country-wide rail system under computer control with each car individually powered, delivering merchandise directly from port to city overnight without trucks on roads. The rail infrastructure is there and under-used because it runs on Victorian rules. > The rail infrastructure is there and > under-used because it runs on Victorian rules. Whose rail infrastrucuture rules are Victorian ? Graham > Batteries are not very efficient > for rapid charge and discharge cycles. As a guess let's say you get > 60% of what you put in back out, with the remainder going to heat. That's why super-caps are used to store the regenerated energy. No such loss. Graham > > Batteries are not very efficient > > for rapid charge and discharge cycles. As a guess let's say you get > > 60% of what you put in back out, with the remainder going to heat. > > That's why super-caps are used to store the regenerated energy. > No such loss. What is a super cap? -- Rich > > > Batteries are not very efficient > > > for rapid charge and discharge cycles. As a guess let's say you get [quoted text clipped - 4 lines] > > What is a super cap ? Have you ever used google ? Graham > > > > Batteries are not very efficient > > > > for rapid charge and discharge cycles. As a guess let's say you get [quoted text clipped - 6 lines] > > Have you ever used google ? What is a google? -- Rich >>>>>Batteries are not very efficient >>>>>for rapid charge and discharge cycles. As a guess let's say you get [quoted text clipped - 8 lines] > > What is a google? Google it and find out.... >>>>> Batteries are not very efficient >>>>> for rapid charge and discharge cycles. As a guess let's say you get [quoted text clipped - 8 lines] > -- > Rich See: http://www.google.com/search?q=google > > Batteries are not very efficient > > for rapid charge and discharge cycles. As a guess let's say you get [quoted text clipped - 3 lines] > > Graham I kinda thought I covered that with, "Using capacitors eliminates the battery losses, but they mean added complexity, cost and weight." > > > Batteries are not very efficient > > > for rapid charge and discharge cycles. As a guess let's say you get [quoted text clipped - 6 lines] > I kinda thought I covered that with, "Using capacitors eliminates the > battery losses, but they mean added complexity, cost and weight." Clearly the added factors are worth it. The also help supply power for acceleration too AIUI. Graham > > > > Batteries are not very efficient > > > > for rapid charge and discharge cycles. As a guess let's say you get [quoted text clipped - 8 lines] > > Clearly the added factors are worth it. No, it is not clear. It all depends on the intended use of the vehicle. For a battery powered electric car intended for use mostly on uncongested highways with few hills the added efficiency of the capacitors may not amount to enough to cover their added weight, to say nothing about the added cost due to the more complex system. > The also help supply power for acceleration too AIUI. Yes, it would be kind of pointless to charge the capcitors up and then not use them to get the car back up to speed wouldn't it. > > > > > Batteries are not very efficient > > > > > for rapid charge and discharge cycles. As a guess let's say you get [quoted text clipped - 14 lines] > capacitors may not amount to enough to cover their added weight, to say > nothing about the added cost due to the more complex system. No-one I know is going to buy a car that won't go up hills and isn't suitable for busy roads. > > The also help supply power for acceleration too AIUI. > > Yes, it would be kind of pointless to charge the capcitors up and then > not use them to get the car back up to speed wouldn't it. You're being disingenuous. The caps are better than batteries at handling large currents overall. Graham > The caps are better than batteries at handling large currents overall. Assuming the two (2) orders of magnitude more weight/energy ain't an issue. Bret Cahill > The caps are better than batteries at handling large currents overall. The best capacitor would need to weigh a few hundred pounds even for a small car. Because of the other inefficiencies, i. e., generating the electricity, regenerative braking would always be a net loss with capacitor energy storage, even on flat land, even braking and accellerating every half mile. Even if a "super cap" was developed the prospect of a short near a lot of Li ion batteries . . . A couple years ago some nut job was trying to get government funding for a "super cap" to power an EV w/o batteries. He was widely ridiculed. Some were posting stuff like the cap equivalent to 15 gallons of gas would weigh 100 tons. Finally I inquired as to the size of the crater a fully charged "super cap" would leave in the road from a short, assuming a super cap could be developed. A poster calculated it would be equivalent to several hundred pounds of TNT if it didn't discharge so much faster than the TNT reaction. The crater would be at least 30' in diameter. I haven't heard a peep about cap power since. Bret Cahill > > The caps are better than batteries at handling large currents overall. > [quoted text clipped - 3 lines] > capacitor energy storage, even on flat land, even braking and > accellerating every half mile. You're talking total bollocks. Do you just make this stuff up ? It sounds like it for sure. Graham > > > The caps are better than batteries at handling large currents overall. Make that "large currents for a very short time, much shorter than the 4 seconds it takes for a Tesla to get to 60 mph." In other words, the energy density is 2 orders of magnitude less than a battery. > > The best capacitor would need to weigh a few hundred pounds even for a > > small car. Because of the other inefficiencies, i. e., generating the > > electricity, regenerative braking would always be a net loss with > > capacitor energy storage, even on flat land, even braking and > > accellerating every half mile. > You're talking total bollocks. You know the energy density of a "super cap?" Bret Cahill "Bret Cahill" <BretCahill@aol.com> wrote in message Sweet f.ck-all. Shut the f.ck up, idiot. > > > > The caps are better than batteries at handling large currents overall. > [quoted text clipped - 3 lines] > In other words, the energy density is 2 orders of magnitude less than a > battery. So ? > > > The best capacitor would need to weigh a few hundred pounds even for a > > > small car. Because of the other inefficiencies, i. e., generating the [quoted text clipped - 5 lines] > > You know the energy density of a "super cap?" I know that it's irrelevant to this argument. Graham > > > > The best capacitor would need to weigh a few hundred pounds even for a > > > > small car. Because of the other inefficiencies, i. e., generating the > > > > electricity, regenerative braking would always be a net loss with > > > > capacitor energy storage, even on flat land, even braking and > > > > accellerating every half mile. > > > You're talking total bollocks. > > You know the energy density of a "super cap?" > I know that it's irrelevant to this argument. It's irrelevant that the energy required to haul around a massive capacitor is more than any savings from the regenerative system? Bret Cahill > > > > > The best capacitor would need to weigh a few hundred pounds even for a > > > > > small car. Because of the other inefficiencies, i. e., generating the [quoted text clipped - 10 lines] > It's irrelevant that the energy required to haul around a massive > capacitor is more than any savings from the regenerative system? What energy is invoved in hauling that weight around ? Graham >>>>>>The best capacitor would need to weigh a few hundred pounds even for a >>>>>>small car. Because of the other inefficiencies, i. e., generating the [quoted text clipped - 14 lines] > > Graham Steady state, a little. Accelerating, quite a bit. Due to the fact that you can never get back quite what you put in due to frictional losses, lighter is always better, even in a regenerative-braking scenario. Not even considering the effects on handling etc. nate Signaturereplace "fly" with "com" to reply. http://home.comcast.net/~njnagel > >>>>>>The best capacitor would need to weigh a few hundred pounds even for a > >>>>>>small car. Because of the other inefficiencies, i. e., generating the [quoted text clipped - 16 lines] > > Steady state, a little. Very little. That's why they do it because it improves the other too in return. > Accelerating, quite a bit. Due to the fact > that you can never get back quite what you put in due to frictional > losses, lighter is always better, even in a regenerative-braking > scenario. Not even considering the effects on handling etc. Having the super-cap improves regenerative efficiency and prolongs battery life. It can also improve acceleration. Using one is a no-brainer until battery technology improves more wrt high rates of charge and discharge and their effect on battery life. Graham > > Steady state, a little. > Very little. That's why they do it because it improves the other too in return. > > Accelerating, quite a bit. Due to the fact > > that you can never get back quite what you put in due to frictional > > losses, lighter is always better, even in a regenerative-braking > > scenario. Not even considering the effects on handling etc. The other inefficiencies in the system are so great that the cap people have a really big hurdle to jump, assuming releasing energy in a short [hundreds of magawatts] isn't a safety issue. > Having the super-cap improves regenerative efficiency and prolongs battery life. Obviously not enough to justify using caps. > It can also improve acceleration. Using one is a no-brainer until battery > technology improves more wrt high rates of charge and discharge and their effect > on battery life. Could you find a device with performance characteristics somewhere between caps and batteries? I guarantee you'll become a billionaire, Nobel Laureate, get a nat'l forest renamed after you . . . Bret Cahill . > > > Steady state, a little. > [quoted text clipped - 22 lines] > I guarantee you'll become a billionaire, Nobel Laureate, get a nat'l > forest renamed after you . . . Why don't you actually read what I wrote ? It's painfully obvious why ultra-caps are used and why they're a good idea overall. By all means stick with your uninformed, uneductated notions. It certainly won't affect me. No one who *is* informed will listen to you anyway. Stupidity and ignorance have no useful value. Graham > It's irrelevant that the energy required to haul around a massive > capacitor is more than any savings from the regenerative system? ====================================== The Maxwell site says their modules handle 125V, put out 750A max, handle 1 million charge cycles, hold 101Wh, have Energy density of 3.8 Wh/kg, Power density of 7.9 KW/kg BobG schrieb: >> It's irrelevant that the energy required to haul around a massive >> capacitor is more than any savings from the regenerative system? > ====================================== > The Maxwell site says their modules handle 125V, put out 750A max, > handle 1 million charge cycles, some also say this is decreased significantly with full charge and elevated temperatures... hold 101Wh, have Energy density of 3.8 > Wh/kg, Power density of 7.9 KW/kg The energy density depends on the voltage levels - the buck boost converter is the limiting factor. So please mention the lower and upper voltage for this values. I wonder if solid Li-Polymer will be the winner of the match or a hybrid solution including a small ultracap and a battery in one package. Gfried www.hyperbike.cc www.greenfleet.info > The energy density depends on the voltage levels - the buck boost > converter is the limiting factor. So please mention the lower and upper > voltage for this values. ======================================== They give the E and P per kg data for their 48V module, but they have a 125V module that only listed the 101 Wh and 750 A max spec, so I assume thats at 125V > > It's irrelevant that the energy required to haul around a massive > > capacitor is more than any savings from the regenerative system? > The Maxwell site says their modules handle 125V, put out 750A max, > handle 1 million charge cycles, hold 101Wh, have Energy density of 3.8 > Wh/kg, Power density of 7.9 KW/kg A 58 lb capacitor can only hold one cent worth of electricity? For how long? Until the light changes? What does it look like after it shorts out? Are trial lawyers salivating at the prospect of being able to cross examine a cap manufacturer, "you either knew or _should have known_ blah blah blah . . ." All regenerative braking vehicles have quick discharge batteries on them anyway so 100 kW isn't such a big deal. Supposedly the 7000 lap top batteries in the Tesla put out 200 kW. Caps might make more sense in power assisted bicycle commuting on flat land. You pedal up to the intersection as you brake to charge up the cap. A 2 lb cap could get you across an intersection w/o damaging your knees. And if a motorist strikes the cyclist, it'll be the LAST cyclist he'll ever hit. Bret Cahill In article <1166647118.066721.282230@t46g2000cwa.googlegroups.com>, "BobG" <bobgardner@aol.com> writes: >Bret Cahill wrote: >> It's irrelevant that the energy required to haul around a massive [quoted text clipped - 3 lines] >handle 1 million charge cycles, hold 101Wh, have Energy density of 3.8 >Wh/kg, Power density of 7.9 KW/kg Aha. Nice, so you can copy and paste numbers. Now, can you also judge whether these numbers are good enough or not. Mati Meron | "When you argue with a fool, meron@cars.uchicago.edu | chances are he is doing just the same" > > > > > > Batteries are not very efficient > > > > > > for rapid charge and discharge cycles. As a guess let's say you get [quoted text clipped - 17 lines] > No-one I know is going to buy a car that won't go up hills and isn't suitable for busy > roads. Who said anything about a car that couldn't do hills or busy roads? The car could still do them, and would still have regenerative braking using batteries. It would just be a bit less efficient at recovering energy under some circumstances, which do not apply for many users. Ever been out to the plains states? There are huge parts of the earth that are flat and are not built up enough to have stop and go traffic. While capacitors may work better than batteries for stop and go traffic or small hills you are not going to store enough energy in any reasonable package to be able to climb a moutain pass through the rockies. And they will not be able to store all the energy from the trip down the other side. > > > The also help supply power for acceleration too AIUI. > > [quoted text clipped - 4 lines] > > The caps are better than batteries at handling large currents overall. I was poking fun at your restatement of the obvious. The main purpose of regenerative braking is to recover energy to extend the range of the car. I even gave an example of getting back up to a certain speed using the energy recovered. For you to the come out with, "The also help supply power for acceleration too AIUI." was just too funny. > Ever been out to the plains states? There are huge parts of the earth > that are flat and are not built up enough to have stop and go traffic. And what's the use of car you can only viably use there Graham > > Ever been out to the plains states? There are huge parts of the earth > > that are flat and are not built up enough to have stop and go traffic. > > And what's the use of car you can only viably use there > > Graham You do have a reading problem don't you? The car would be fine to use other places. It just wouldn't have the added expense of the system you are advocating which would optimize it for conditions that don't apply everywhere. > > > Ever been out to the plains states? There are huge parts of the earth > > > that are flat and are not built up enough to have stop and go traffic. [quoted text clipped - 7 lines] > you are advocating which would optimize it for conditions that don't > apply everywhere. It wouldn't sell except in small numbers so don't expect it to happen. Graham > > You're being disingenuous. > > [quoted text clipped - 5 lines] > using the energy recovered. For you to the come out with, "The also > help supply power for acceleration too AIUI." was just too funny. You clearly don't know much about the effect on batteries of high charge and discharge rates. Your display your ignorance admirably well. Graham > You clearly don't know much about the effect on batteries of high charge and discharge > rates. We're still waiting for you to compare the energy density of the best capacitors to batteries. Bret Cahill |> You clearly don't know much about the effect on batteries of high charge and discharge | > rates. | | We're still waiting for you to compare the energy density of the best | capacitors to batteries. Shut the f.ck up, imbecile. http://www.popularmechanics.com/blogs/automotive_news/3423261.html > > You clearly don't know much about the effect on batteries of high charge and > > > discharge rates. > > We're still waiting for you to compare the energy density of the best > capacitors to batteries. Energy density has very little to do with it. Graham > > > You clearly don't know much about the effect on batteries of high charge and > > > > discharge rates. > > We're still waiting for you to compare the energy density of the best > > capacitors to batteries. > Energy density has very little to do with it. It doesn't matter if the capacitor must weigh over 400 lbs to store enough energy to get a small car up to 30 mph? Bret Cahill > > > You're being disingenuous. > > > [quoted text clipped - 12 lines] > > Graham With a large enough battery pack the charge and discharge rates become relativly small. > > > > You're being disingenuous. > > > > [quoted text clipped - 15 lines] > With a large enough battery pack the charge and discharge rates become > relativly small. However the move is to smaller and lighter battery packs for economy. Graham > Something to keep in mind is the energy of a moving vehicle is > proportional to the square of its velocity. So a car doing 30 mph with > a 50% recovery system could get back up to about 21 mph on the > recovered energy. Shows how it can make a big difference in stop and > go city driving. You have to account for the efficiency losses during acceleration, too. The controllers lose some as heat, the motors lose more, then there's tires, gearing, and so on. Probably wouldn't get more than 15 mph out of it. Dan | > Something to keep in mind is the energy of a moving vehicle is | > proportional to the square of its velocity. So a car doing 30 mph with [quoted text clipped - 6 lines] | there's tires, gearing, and so on. Probably wouldn't get more than 15 | mph out of it. Dan http://library.witpress.com/pages/PaperInfo.asp?PaperID=3256 http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?tp=&arnumber=878901 http://www.vyconenergy.com/faq.asp http://www.llnl.gov/str/pdfs/04_96.2.pdf > http://www.llnl.gov/str/pdfs/04_96.2.pdf This last one doc is quite intersting.Energy density is not that high in the order of 100 Wh per kg (vs > 150 Wh/kg of lithium),but it's still useful in electric vehicles.Moreover,number of cycles efficiencies are better and use no hazard chemical (although lithium is not so dangerous or polluting) | > http://www.llnl.gov/str/pdfs/04_96.2.pdf | | This last one doc is quite intersting.Energy density is not that high in the | order of 100 Wh per kg (vs > 150 Wh/kg of lithium),but it's still useful in | electric vehicles.Moreover,number of cycles efficiencies are better and use | no hazard chemical (although lithium is not so dangerous or polluting) Yes, once we get past the popular press and the nay-sayers there is much that is left unexplored in energy conservation. > > Something to keep in mind is the energy of a moving vehicle is > > proportional to the square of its velocity. So a car doing 30 mph with [quoted text clipped - 8 lines] > > Dan The losses during acceleration were figured in. I had previously written, "Figure the motor/generator itself is 90% to 95% efficient. That would mean that you would lose 5 to 10% putting the energy into storage, then another 5 to 10% converting it back to mechanical energy. If the battery pack is used to store the energy, it has internal resistance so some of the energy is lost as heat. Batteries are not very efficient for rapid charge and discharge cycles. As a guess let's say you get 60% of what you put in back out, with the remainder going to heat. So you could be looking at 90%*90%*60%=48.6% " Using average rather than low end numbers the above would be 92.5%*92.5%*60%=51.3% The 90% to 95% efficiency includes losses in the controller. These motor/generators are well proven out in industrial machinery. No need to reinvent the wheel for automotive use. > > What is the efficiency of regenerative braking in electric > > vehicles? How much kinetic energy is recovered? [quoted text clipped - 6 lines] > figures you find will depend on whether you're looking solely at the > efficiency of the motor during regenerative braking, ? > the amount of energy that ends up the batteries, or the > ount of *recoverable* energy that ends up in the batteries -- Only the amount recoverable is useful. Why would that not be the same as went into the batteries - heat losses, overcharging? > the figures for each will all be > different. It isn't clear to me which the Wikipedia article refers to. -- Rich > What is the efficiency of regenerative braking in electric vehicles? > How much kinetic energy is recovered? The new stock being planned for the shallow lines of the Lodnon Underground will have regenerative braking; the press release [1] says: "The new trains will also have regenerative braking systems, which recycle energy that, on current sub-surface lines trains, is lost in braking. This will save about 20-25 per cent of that energy, making a real contribution towards tackling CO2 emissions." tom [1] http://www.tfl.gov.uk/tfl/press-centre/press-releases/press-releases-content.asp ?prID=961 SignatureTHE DRUMMER FROM DEF LEPPARD'S ONLY GOT ONE ARM! > "The new trains will also have regenerative braking systems, which recycle > energy that, on current sub-surface lines trains, is lost in braking. > This will save about 20-25 per cent of that energy, making a real > contribution towards tackling CO2 emissions." Energy lost to friction braking is probably more than wind and rolling resistance combined for a commuter train. Still, it seems they could do a little better than 20 - 25% considering economies of scale. > [1] http://www.tfl.gov.uk/tfl/press-centre/press-releases/press-releases-content.asp ?prID=961 Bret Cahill |> "The new trains will also have regenerative braking systems, which recycle | > energy that, on current sub-surface lines trains, is lost in braking. [quoted text clipped - 3 lines] | | Energy lost to friction braking is probably Probably you are 95% ignorant, 5% troll, shithead, but sure don't want to learn, arsehole. more than wind and rolling | resistance combined for a commuter train. | [quoted text clipped - 4 lines] | | Bret Cahill > What is the efficiency of regenerative braking in electric > vehicles? How much kinetic energy is recovered? > > -- > Rich The last numbers I saw from Toyota claimed the regenerative braking system on the Prius was capable of a 30% recovery rate. http://www.toyota-hawaii.com/vehicles/Prius/braking.html A life cycle assessment by CNW Marketing/Research [20] does however show that the Prius uses more energy than the average car, and also more energy than several larger cars such as the Hummer H3. Toyota's own life cycle assessment also shows that the amount of energy required to manufacture a Prius is higher than that of a similar gasoline powered vehicle. SignatureSteve W. > What is the efficiency of regenerative braking in electric > vehicles? How much kinetic energy is recovered? In principle it's 100%, since that's the only reason stationary bicycles. and Gold's Gym works. In practice, it depends more on battery cable gauge than physics, > -- > Rich Batteries require at least 160 % to recharge . If you get 100 % , it will take at least 1.6 times that energy to charge the batt' . Electric Braking wears few parts , so its a good idea . But you must apply current to a rotor to make magnetic flux , to produce amperage in the stator . But it does work well , as our cars have alternators that are efficient , taking only 20 watts rotor for 700 watts at the stator . They have a wide speed range . Car alternators will work well between 1000 and 10,000 RPM . I dont like 10,000 RPM for the wear/tear on ball bearings/needle bearings . I prefer less than 6000 . First pick a good motor , then design braking . BTW Wind generators can use car alt' well , keep the output in 3 phase and above 40 volts til it reaches the batteries , then switch mode "buck" regulate to charge battteries . And SCR's can be used to modify the output to run 60hz appliances . 3 phase to single phase , by switching the 3 windings at the proper time . U need 6 SCR's for a Delta wound . BTW , OT .. fully discharge a NimH battery ? Nikon ( S-4 digi-cam) says you must fully discharge their batteries occasionaly .. What do you think ? Lead Acid batteries , sulfate , but NimH are opposite electrolyte , its alkaline . Is there a similar effect to sulfation in hydroxide in a dry AA NimH cell ? > What is the efficiency of regenerative braking in electric > vehicles? How much kinetic energy is recovered? > > -- > Rich > Batteries require at least 160 % to recharge . If you get 100 % , it > will take at least 1.6 times that energy to charge the batt' . [quoted text clipped - 29 lines] > opposite > electrolyte , its alkaline Lead Acid batteries are always the wrong choice unless you enjoy being in permanent debt to the government. Since the primary attraction of wind energy is that it can reduce the cost of power meters to zero, . Is there a similar effect to sulfation > in hydroxide > in a dry AA NimH cell ? [quoted text clipped - 4 lines] > > -- > > Rich |
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