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@kelly, You cannot just parallel supercaps to battery. There would be nothing to prevent current surge from battery to suppercaps when motor gets heavily loaded (during acceleration). Also current would rush to battery during strong regen braking (because battery and supercaps are directly connected, meaning the voltage will be the same) The right way to use (larger) supercaps with battery in BEVs (and PHEVs) is to put a two-way DC-DC converter between supercaps and battery, which would limit max current that goes from/into battery. Some simulations have shown that for some standard US driving cycles, for passenger cars, you could use supercap bank of no more than 200 Wh (3/4 of that being available, i.e. 1/2 VMAX discarge). That configuration could provide up to 3x max current of the battery pack, for short periods required in those driving cycles. So by employing an extra two-way DC-DC converter you'd limit the max battery current, for the same max motor current. Also battery life could be significantly extended, as most current spikes would go through supercaps, not through battery The price to pay for that benefit is extra DC-DC converter (sized for about 1/3 max motor current), and the supercaps bank. Supercaps are reportedly still very expensive - someone recently mentioned here $15,000 per kWh. I think that for the price of PHEVs to become affordable (the ones with smaller battery pack, paired with supercaps, used this way), the price of supercaps needs to drop by at least 60%, to $6,000/kWh. I expect the price of power components (for DC-DC) to keep going down, as it was always the case with mass produced electronics. It looks very likely that batteries will always have to be designed either for high power (ie current) density, or for high energy density. Once supercaps become much more affordable, small battery PHEVs will be possible, supercaps will provide high currents for short acceleration and braking periods. Another advantage of this configuration is that the car can run in HEV mode with completely removed battery pack, just with supercaps bank. It would also increase resale price of older cars, with weak battery pack.
"the old problem of poor lean-mixture ignition" To me it appears they are trying to create a spark with more energy to ignite the mixture. The added capacitive element probably makes the spark last a bit longer - more igniting power. I saw some attempts to make stronger spark - Spark plugs with V-groove in the center electrode, Twin-Spark ie 2 spark plugs in Alfa Romeo, Mercedes also used 2 in some engines earlier. I don't know about what racing engines use. I wonder if instead of single tip spark plug, a better option would be using a two concentric rings, one having at least 4 small bulges that would act as mini spark plugs to create "ring of fire". It all would require a larger/wider spark plug, and space in cylinder head is already crowded with several valves. Could the valves be moved to the edge of cylinder head, could the cylinder be widened a little bit near top to accommodate wider spark plug and (still round) valves? Say if cylinder bore is 75 mm, spark plug's new "ring of fire" to have a diameter 18-25 mm. Much larger surface would get initially ignited, but if this is what's needed, I don't know, or how it would reflect on NOx emissions. For sure it would ensure mixture is better ignited, I guess HC emissions would be lower. Another possible benefit: Currently, with single point (just center) ignition, if mixture happen to be too lean in centre (as a result of all the turbulence - uneven mixture), it may fail to ignite properly. But if sparks are fired around the ring, somewhere there will be mixture rich enough to ignite. I wonder if "ring of fire" would help to direct shock wave mostly downwards. With centre-pin spark, I guess the shock wave also travels towards cylinder walls (ie goes in all directions), then bounces.
@E-P, Do you believe more American technical experts, or mainstream media - it's up to you. This is what experts said: (I'm pretty sure Mannstein is familiar with this). Try googling the following expression "countries bombed by usa" It's a long, long list.
@Jus7tme Diesel Plug-in hybrid is NOT the way to go. Non-plug-in Diesel hybrid may be. Diesel Plug-in hybrid simply amplifies disadvantages of diesel: Higher weight and higher price than gasoline models. Usually people either drive a lot in the city, or inter cities. Those who spend most time in city driving should buy cheaper (and lighter) gasoline plug-in model. Those who drive mostly outside cities, should buy a diesel or hybridized diesels, with a very small battery, not to carry all the time heavy battery, which is just a dead weight on long trips.
@ Roger, It is often said that turbochargers for gasoline engines have to work with exhaust gasses with temperature that is 100-150 degC higher the gasses from diesel engines, so they need to use more expensive materials, and are perhaps likely to last less than turbos for diesel engines. Atkinsonized gasoline engines, with high expansion ratio are supposed to produce gasses with lower temperatures, than non-Atkinsonized ones. Any idea how much less hot those exhaust gasses in Atkinsonized gasoline engines are? Could they use turbochargers for diesel engines?
@ Roger, it says "... the electric pump which is driven directly by its motor so these seals could be eliminated. Resin protects the electric motor parts from rust." Does it mean that coolant, and not air, is between rotor and stator of the pump e-motor? So it's not air-gap, but "water gap". If it is the case, then it assumes smooth perimeter of rotor, i.e. without protruding pieces, like in switched reluctance motors, which are cheaper and more heat tolerant than PM motors. What about bearings, are they also lubricated by the coolant (if there are no seals, coolant goes anywhere around moving parts)? BTW, any idea how powerful those e-motors need to be for passenger cars.
I wonder why in USA cars like Toyota Corolla, Honda Civic come with cheaper (and inferior) rear DRUM BRAKES, while in Europe (and Australia) those models use rear DISCS. In US, only top end model of Honda Civic comes with discs. Corolla doesn't even has an option of rear discs. This 2013 Nissan Sentra also has rear drums. On the other hand, Mazda3, VW Golf, Mitsubishi Lancer all have rear discs on all trim levels.
@E-P, I know that it can be done that way. They might have used some more advanced solution, you can never know that something better wasn't invented. Perhaps here some hydraulic device with fast-acting digital valves. I'm pretty sure that they'd use something else if creep mode was to be used some sigificant percentage of time, otherwise clutch wouldn't last long.
@T2, Sorry I didn't see your post. I agree with your analysis of efficiency and advantages of high speed e-motors. I think that motor MG2 of Toyota Prius (latest PSD - 2010 model release) doesn't exceed 14,000 rpm. I have two numbers for max rpm of MG2: 13,500 and 12,400 rpm. MG1 in previous versions had about the same max rpm as MG2. Bosch has two (scalable with length) versions of their so called SMG (PM based) motors for hybrids, with 180 and 138 mm diameter. The 180 mm one has max rpm of 14,000 rpm, and the 138 mm one has Max rpm = 18,000 rpm. Possibly the reason for lower max rpm of larger diameter motor is higher moment of inertia (goes with square of radius), which causes more bearing load. Higher rpm also have some rotor components retention issues. I think that for very high rpm motors (13,000 rpm and up) it's preferable that L/D ratio is >1, preferably up to 2 (? cooling issues in the centre of rotor). Tesla roadster's motor looks a bit elongated. Perhaps in elongated motors, rotor cooling at the centre is more difficult in PM rotors than in cage copper rotors. Regarding coasting (aka sailing/gliding) with PM motors - recently released hybrids from BMW and Mercedes use it (turn of the engine) when gas pedal is released at speeds of up to 150 kmph (forgot the exact number). They both use ZF pre-transmission PM motor, now a 40 kW one. If they somehow can disconnect coils, then the drag torque would only be caused by currents induced in laminations - probably much smaller drag than from rolling and air resistance. What do you think of using TWO PHASE IM (TPIM) motor, four pole, instead of 3 phase one (also four pole)? Found this for motor design: "Criteria also required a minimum number of poles to minimize stator losses.". Wouldn't it then favor 2 over 3 phases ? It would require less space at the stator circumference to put all the coils, and smaller radius allows higher rpm.
Given the low power density of Envia batteries, they are just suitable for BEVs, with large battery pack, so they can develop enough power. In a smaller battery pack, they'd need to be paired with ultracaps (with two-way inverter) to be able to develop sufficient power for acceleration (in PHEVs).
As this is a non-synchronized transmission, they must be using some automated double clutching for shifting, adjusting engine rpm in the process. Probably the shift time is not quick (if it was, they'd have mentioned it). Obviously there is a planetary gear stage (? on the left) that extends number of forward gears from 4 (3 constantly meshed plus a direct gear) to 12. Just wonder how they implement the creep mode.
@E-P, BTW, did you notice some of the claimed improvements in the new hybrid transmission: - Electric motors capable of operating at higher electric speeds; - Reduced weight The goals were higher efficiency, and as always - lower costs.
Harvey, in Europe another HP is used for vehicle power: ... Mazda3 ... den 2.0 l MZR 110 kW (150 PS) oder den 1.6 l MZR-CD 85 kW (115 PS)! and: 1598cc in-line 4-cylinder, 16-valve, DOHC, 105ps (77kW) at 6000rpm and 145Nm at 4000rpm There 1 HP = 0.733 kW (1 kw ~ 1.36 HP or PS) See: and Wiki - Horsepower Another thing - l/100Km or Km/l (or mpg). Usually all consumer goods prices are expressed as say $/lb, $/kg, $/oz, $/bbl, and not kg/$. European "l/100Km" mostly follows that pattern, ie how many litres to buy for 100 km. American mpg reminds of vehicle range, like miles per tank. Probably comes from the time when fuel was ridiculously cheap in US, cheaper than drinking water. It used to be "Fill'er up". When fuel is expensive, you may fill just half, if driving infrequently. Perhaps now that fuel is not that cheap in US, it makes more sense to use quarts per 100 miles, than mpg. It could make it easier to calculate how much fuel you have to buy.
@ Harvey, There are some e-motors used in recently launched EVs with low power density. For example e-motors in Renault EV Fluence, and Kangoo electric. On their specs page (French) I found they use motor of 130 kg developing about 50 kW. Big difference in power densities between those motors (I think made by Continental, synchronous AC with slip rings), and the one from Tesla roadster.
Statement: "Power density is about twice that of today’s motors, according to GE." is very misleading, tells little. If they were sure of superiority of their design, they'd for sure have said how many kW/kg, as some axial flux motor makers did. BTW Bosch already makes similar motors, a whole range. PSA Peugeot Citroen uses Bosch motor to drive rear wheels in their through-the-road hybrid.
Doubling the pole count halves the speed but doubles the torque for the same frequency; double the frequency to return to the previous speed, and power is doubled. One thing you missed here. It's not enough to just double frequency, you also need to double input voltage (at least for induction motors), otherwise you'd get something for nothing (to double output power). Effective value of a sinusoidal current (or voltage) depends on amplitude only, not on frequency.
In this picture the Safran SMA engine shape reminds me of the OPOC engine, by EcoMotors ( Just wonder if the OPOC Engine could be used in aircraft. The designers said the first application to be for trucks, although it naturally looks as an aircraft engine, and would probably have less packaging issues than in trucks.
Roger, Would it make sense to downsize Prius (or Prius C, or some other HEV's Atkinsonized engine) by adding an electric supercharger, driven from high voltage bus, already available. Say instead of 1.5L 4-cyl, use 1.2L or 1.0L, 3-cyl engine w/ electric supercharger. I think electric superchargers, with independent boost control, are cheaper than the positive displacement ones (like the Roots-type one used in Nissan Micra, 3-cyl). Would it be too expensive?
@E-P, How do you think AC Propulsion gets 200 horsepower out of an induction motor weighing just 70 pounds? I know about that motor, used in Tesla roadster, first generation. Later they increased mass to 110 lbs. Max rpm is over 13,000 rpm meaning they run it up to about 450 Hz. Isn't it a prime example of an induction motor having such power density thanks to high max rpm. Two pole, or 4-pole, but not 16 poles. Quote from the Austin Hughes book on e-motors, 3rd edition, page 41: Output power per unit volume is directly proportional to speed. Low speed motors are unattractive because they are large, and therefore expensive. It is usually much better to use a high-speed motor with a mechanical speed reduction. I admit, I'm not a motor expert, but know something. The guy 'T2' was probably the most knowledgeable to comment on motors, especially induction ones. I mentioned axial just to avoid confusion. Did you think of that Honda IMA pancake motor example I mentioned, would it work that way?
@Roger Pham, I trust your info and calculations. Looks like the mentioned LiFePO4 battery is even suitable for a HEV using an e-motor up to 50 kW short burst (w/ battery pack size of 1.3 kWh). The larger battery pack will handle the same power burst with less stress (ie heating less). This battery pack is perhaps the best (ie cheapest) choice at this point in time for the purpose. Still some issues remain: - Do the high power/current bursts reduce battery cycle life and by how much? Recent article here ( stated: "operating a battery at a temperature of 45°C instead of 35°C halves its service life." The use of ultracap as buffer would significantly reduce battery in and out currents, thus reduce heating and particularly max current spikes that can be very stressful and life shortening. - If inexpensive ultracaps are available, wouldn't it be more economical to use batteries with twice energy density, and half power density, that cost the same per kilo (kg) - this is very speculative, assumes that power density can be traded for energy density during design. - In ultracap-battery combination, ultracaps are expected to last 3 or more times longer than batteries. Once battery pack reaches end of life, it can be electronically (also manually) disconnected from the rest of the system and the car works as a non-plug-in HEV, using just ultracaps - no need (and no fear at purchase time) for immediate battery replacement, car is still usable as a HEV. - Say you have a plug-in hybrid with 8 kWh battery (plus ICE). You park it with SOC near minimum, leave it parked for a month or two, or even just 2 weeks, depends on battery chemistry (say long vacation, or whatever reason). Battery self discharges. If you have a 'permanent' battery, i.e. some 12 or 24 volt, that is supposed to last 3-6 months charged, you might be able to start ICE. But you won't be able to use any electric motor assistance, until you recharge the large (8 kWh) battery pack. Either by connecting it to grid, or running car motor/generator, say of 10 kW, for about 15 min or longer (being stationary, not driving), to reach some minimum SOC of say 25%. But if you had ultracap-battery combo, you could charge the capacitor from the standard battery (12 volt) in less than 2 min, to 1/3 SOC (ultracap pack say 300 Wh, Min SOC is 1/4 ie 75 Wh, or 1/2 of max voltage for ultracaps, it's a convention to count that way). So with combo you can drive the car as HEV (using only 300 Wh ultracap module), with full e-motor assistance. You recharge large battery when you get chance, car is always drivable. So I'd say combo still has advantages over pure battery storage for PHEVs.
@E-P, I tried to follow what you are saying. I assumed you talked about a radial machine, not axial one like the one used in this text. Apparently you assumed that there were enough room to insert more magnets among existing ones, along circumference. I understood properly, you made new magnets by cutting the original cylindrical magnet so that circular surface remained the same, only you reduced the height, so new magnets are shorter in height. If it is the case (ie there was empty space for new magnets around), then original design was inefficient. On the other hand if you reduced the surface (and not height) along which two magnets face one another (rotor and stator), then you also reduced the pulling/repealing force, and it is not a right way to prove something here. I still believe that you cannot add new poles, that generate the same magnetic flux as old one (with the same current), without increasing the diameter of the motor. Put it the other way around: Say you removed 1/2 of poles from a pancake motor (say Honda IMA), so holes appear between poles. You can then simply reduce the radius, pack remaining poles tightly, and make the motor smaller/lighter. Drive it at the same rpm, but now with half torque, so it would produce only 1/2 the original power at given rpm?
@E-P, Let's assume your statement (at 04:06 AM) is true. But is it possible to increase the pole count (say to double or triple them) without increasing the motor diameter (assuming the same physical size of new and old poles to produce the same pulling force)? The visually simplest case would probably be the switched reluctance motor.
The fact is that currently no major car maker plans to release a car with in-wheel motor. Some went with in-wheel concept (VW) or racing car (Toyota) and stopped there. They probably learned something, and are no longer mentioning it. At the same time they experiment with fuel cells and hydrogen. It implies that major car makers are less optimistic about in-wheel motors than even about fuel cells. In-wheel motors must be high-torque motors (they spin at low speed, below 2,000 rpm). The fact is that for the same power output, high rpm e-motors have significantly lower mass than low-speed (high-torque) ones. No wonder that Tesla roadster, Toyota Prius (post 2010 model), Nissan Leaf, all use e-motors with max rpm over 10,000 rpm.
It will be a looong time before Ford can match Toyota's reliability.