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Regarding the thick cables needed for 600 Amp DC currents, here are some statements from a document on 48V from site Zwei.org. "There is a common ground for the 12/24-volt system and the 48-volt system, which are connected via physically separate rounding bolts/connections.". Also "no isolated grounding (B-) required". It means that for negative, i.e. ground, a thick aluminum rail can be used, which is half the weight (compared with a copper conductor of same ampacity), and cheaper than copper. That Alu rail wouldn't need to be isolated from the chassis. Copper cables (or rail) can be attached to Alu rail via bimetal washers (Alu with deposited layer of Cu) and bolts. It can be considered dry environment (for Alu-co connection). For HV systems, both positive and negative battery cables (to inverter(s)) need to be isolated. I read in a study done by UBS that HV isolation costs more than $1,000 per car for a PHEV. For PHEVs with 2 or 3 traction e-motors (AWD system) it may make sense to use 48V system, with these 30 kW motors, to reduce costs. Even better if some of the used e-motors are paired with multi-speed transmission. Hyundai Sonata, 1st gen. PHEV used 50 kW e-motor with transmission (P2 system).
The recently announced BEV models: Mercedes-Benz EQC and Audi e-tron both have induction motors. Germans call them "asynchronous motors", it is the same thing. Both models are AWD, use two e-axles (2 motors per vehicle, both induction ones).
This vehicle seems to be the first 48-volt PHEV. Here they use 2 e-motors of 25 kW peak, which is a max that I saw for a 48-volt motor (52-volt x 500 amps, probably for 10-20 sec). For a passenger car (B or C class) two or three such e-motors (say one integrated in ICE's transmission ), 20-25 kW peak each, can be used for a PHEV. I read somewhere that mandatory isolation for high voltage battery costs manufacturers more than US$1,000 per vehicle, possibly twice that amount. Tilting mechanisms are complex and probably expensive to produce. A sudden failure of such mechanism is likely to be fatal for the driver. As vehicles become older probability of a component failure goes up.
Voltage limit rules "anything-to-anything" already don't apply to engine block heaters that have been used for decades in Canada. That option is available on many cars, people plug it into wall socket with AC 120V, 60 Hz. The industrial rules for low voltage 60V could be relaxed for cars. They can be defined for +/-48V as anything-to-anything within 10 or 12 inches. Also a mechanical switch may be required at the battery connection for -48V, that is turned on only when 'key' is inserted, turned off when key is out, or airbag sensor detects crash. It is already environment where hundreds and thousands lose their lives because of speed and stupidity. Far more dangerous thing is to allow self driving cars when a malfunctioning sensor or software bug can kill people. No double or triple redundancy is required for self-driving cars, as it is a required in civil aviation, at least I haven't read about it. It would make such cars too expensive.
It may be about time to develop a new specification for low voltage (48 V) system in cars. The system that uses both +48 Volt and -48 Volt. The idea is to have 2 identical blocks of 48 Volt battery, spatially separated, connected to chassis with mid point, the 2 battery modules are connected in series, providing 96 Volt that can be used for drive motor(s). As the module providing 48V will be loaded more heavily (for 12V and 48V accessories), there will be need for one isolated DC-DC converter that takes power from negative battery module and charges positive battery module. Drive motors that offer boost and regen are driven by inverters connected to 96V battery, and they charge both modules in series (96V). Schaeffler 48V electric axle develops 20 kW with apparently one e-motor. http://www.greencarcongress.com/2017/01/20170110-shaeffler.html With 96V two e-motors could produce 2 x 40 = 80 kW which is sufficient for a small or mid size PHEV. With 3 such motors, it can be a BEV. Expensive high voltage protection measures would only be applied to inverter-motor system, they are always one beside the other. Re: Idling rpm control - Honda did something similar long ago in their Insight IMA hybrid. I read somewhere they used e-motor (P1, IMA configuration) to balance their 3-cyl engine.
Honda two-motor hybrid is basically a series hybrid with the ability to connect engine directly to wheels, which is only practical to do at higher car speeds (say highway speeds, some reports say the drive ratio equals 6-th speed in a manual version of the car). It's unable to use powerful generator to contribute torque in EV mode. OTOH GM Voltec 2.0 and Toyota Prius Prime (latest PHEV) added one-way clutch which allows them to use generator as (second) e-motor in EV mode. Honda system in a way wastes resources, generator can only be generator, and it makes the system more expensive, and heavier than competing systems that can use generator also for propulsion in EV mode.
It's said: "Other systems use braking to achieve a similar effect—but waste energy and slow the vehicle in the process." What the GKN system of clutches does if not brake one half shaft to send more torque to another half shaft, using controlled clutch slip. Clutches wear as well. So is it cheaper to replace brake pads, or clutches inside GKN Twinster system? Probably GKN system offers finer control, but is it worth the price?
Why not use 2 such 48 volt e-motors of 20 kW (continuous output, as above, peak power usually can be 40-50% higher) on the rear axle with e-differential? And make it a PHEV with battery 4-10 kWh. PHEV makes sense even if used just for AC compressor (especially w/ start-stop systems), with 2-4 kW power requirement on a hot day, the car can be pre-conditioned before start. For city (non-agresive) driving, up to 70 km/h on level road 40 kW of power would be sufficient for cars weighing up to 1,300 kg, approx. Strange that nobody even mentions 48V PHEV, and at the same time they keep repeating that 48V (ie 60V) system is significantly cheaper to build (than higher voltages, used for full hybrids) as they don't need to implement high voltage protection. Some may say that as soon as you connect it to 120V (or 220V) AC for charging, it's no longer low voltage system (60 V or less). But many cars in Canada come with block heater that connects directly to 120 V AC, and nobody asks a question. Several very small BEVs use 48V battery and single motor drivetrain, like Mahindra e2o, Renault Twizy. So why not make a 48/60 Volt PHEV with 2 (or 3) e-motors, each 20 kW, as above?
@Harvey, "This will probably produce a VERY LIGHT ... battery" I think it would be more appropriate to say "It'll be a HEAVY battery". This is a language question - what we perceive as light and what as heavy. I never heard that existing lead-acid batteries were called 'light'. Or that anything made of lead was called 'light'. Probably people call a box of certain volume 'heavy' if it is difficult to lift (by hands), and 'light' if it is easy to lift. In other words Prieto battery would appear 'heavier' than other Li-ion batteries. BTW this type of battery is what is needed for plug-in hybrids with sub-10 kWh battery, as used in recent European PHEVs. For a PHEV it is far more important that the battery pack, of fixed energy capacity, takes up 10 liters of space less, than that it weighs 10 kgs less. PHEVs of up to 10 kWh usually don't put battery pack under the floor, like BEVs, but in a limited space under (and around) rear seat. Batteries with high energy density by volume are very desirable for PHEV's, especially if they also have high power density (by volume). From this perspective Toyota's decision to stick with proven NiMH batteries in HEV Prius, until 2016 (? the latest Prius HEV uses Li-ion) looks very reasonable. By using Li-ion batteries they wouldn't have saved (much) space, just some weight (power density might have been another reason for NiMH).
@Harvey, "This will probably produce a VERY LIGHT ... battery" I think it would be more appropriate to say "It'll be a HEAVY battery". This is a language question - what we perceive as light and what as heavy. I never heard that existing lead-acid batteries were called 'light'. Or that anything made of lead was called 'light'. Probably people call a box of certain volume 'heavy' if it is difficult to lift (by hands), and 'light' if it is easy to lift. In other words Prieto battery would appear 'heavier' than other Li-ion batteries. BTW this type of battery is what is needed for plug-in hybrids with sub-10 kWh battery, as used in recent European PHEVs. For a PHEV it is far more important that the battery pack, of fixed energy capacity, takes up 10 liters of space less, than that it weighs 10 kgs less. PHEVs of up to 10 kWh usually don't put battery pack under the floor, like BEVs, but in a limited space under (and around) rear seat. Batteries with high energy density by volume are very desirable for PHEV's, especially if they also have high power density (by volume). From this perspective Toyota's decision to stick with proven NiMH batteries in HEV Prius, until 2016 (? the latest Prius HEV uses Li-ion) looks very reasonable. By using Li-ion batteries they wouldn't have saved (much) space, just some weight (power density might have been another reason for NiMH).
@Harvey, "This will probably produce a VERY LIGHT ... battery" I think it would be more appropriate to say "It'll be a HEAVY battery". This is a language question - what we perceive as light and what as heavy. I never heard that existing lead-acid batteries were called 'light'. Or that anything made of lead was called 'light'. Probably people call a box of certain volume 'heavy' if it is difficult to lift (by hands), and 'light' if it is easy to lift. In other words Prieto battery would appear 'heavier' than other Li-ion batteries. BTW this type of battery is what is needed for plug-in hybrids with sub-10 kWh battery, as used in recent European PHEVs. For a PHEV it is far more important that the battery pack, of fixed energy capacity, takes up 10 liters of space less, than that it weighs 10 kgs less. PHEVs of up to 10 kWh usually don't put battery pack under the floor, like BEVs, but in a limited space under (and around) rear seat. Batteries with high energy density by volume are very desirable for PHEV's, especially if they also have high power density (by volume). From this perspective Toyota's decision to stick with proven NiMH batteries in HEV Prius, until 2016 (? the latest Prius HEV uses Li-ion) looks very reasonable. By using Li-ion batteries they wouldn't have saved (much) space, just some weight (power density might have been another reason for NiMH).
It's too weak motor. With 48 Volt system you can get up to 15 kW peak power, continuous half of that or less. Much better would be to use 2 such motors in some combination. Best in a 2 speed combination (say like in WrightSpeed). Combine it with a 48 Volt rechargeable battery (up to 4 kWh). It makes sense to have rechargeable battery just for AC in stop-n-go traffic in hot climate regions. AC compressor is a 3 kW or stronger motor.
@Brian P., "The Tesla P90D uses ...and two motors in the back" It's first time I read that P90D uses two motors in the rear. Could you please provide some link where it is said. I searched, everywhere it's said that there is only one drive motor in the rear of P90D (with a differential, obviously). Haven't seen yet a Tesla drivetrain with 2 motors in the rear, without dufferential.
@E-P, the mentioned 68KW of electric power in your Ford PHEV, that uses licensed Toyota hybrid system - is it the power of just the stronger (MG2) e-motor, or combined power of MG1 and MG2 as in latest Prius PHEV Prime? The latest Prius PHEV Prime, compared with previous Prius PHEV, has an extra one-way clutch that allows both e-motors to provide torque in BEV mode (similar to new Volt). Just wonder if Ford is allowed to do that modification, and further development of the system it uses, or it's limited by existing Toyota patents. Or Toyota first thought of that (after new Volt).
@Roger, From the link you mentioned for the first motor: http://www.electricmotorsport.com/ev-parts/motors/ac-induction/ac-35x2-165-hp-pk-dual-stator-72-144v-ac-induction-motor-drive-kit.html You chose the one of 125 HP (96 Volt), instead the one of 165 HP (140 Volt) - see table at bottom. The one of 125 HP has higher torque, the other one (165 HP) must have higher max rpm (can be calculated from the data). Apparently both motors cost the same, are of the same weight, same diameter. Looks like it's with aluminum rotor, as efficiency is only 89%. Only the controller for 165 HP motor costs $1,500 more (see options). According to a previous article at GCC inverter prices are below $10/kW. This means that if you can increase speed of induction motor, the price won't be proportional to the power. You will need better bearings (ceramic ones), better balanced rotor. We argued about this issue once earlier - here is proof that you can increase motor power via rpm, without increasing its cost proportionally.
Instead of the two systems above, I'd use system from Wrightspeed with two induction motors per axle, multispeed (2 or 4 speeds, clutchless shifting) to avoid low rpm range of IM where it is very ineficient (and to maximize torque, say for hill climbing). The configuration is not patented by Wrightspeed, only method of dynamic control - there are tens of methods around, everybody uses similar way to control traction. No differential either. Uses cheaper IM motors.
It's said that 48 volt system is significantly cheaper as it doesn't need to implement some high voltage protection features. I read many articles on the web about 48V hybrids, and nowhere they mention even a possibility of using a voltage upconverter from battery to e-motor(s), as in Prius from 2010 (or so) onwards. They can increase 50 V (ie 48 V) to 120-150V, and use 25-30 kW e-motor(s). High voltage would exist only in the inverter-motor compartment, only when motor spins at higher speeds. That way they could easily drive compact cars on flat up to 40-50 kph. New city street limits in Paris are 30 kph, to cover half of streets by the end of 2016, all streets by 2020 (yesterday's news). Prius upconverter raises battery voltage from 280V to 650V (if I remember correctly). With upconverter the 48 Volt PHEV would make sense. Maybe even without upconverter if 2 e-motors are used.
Very promising CHINO-INDIAN invention. Just look at the names of scientists. It's almost a rule for scientific articles published on this site, last almost 10 years. Where are the US born scientists?
@Davemart, What would you be doing during the almost 2 hours (120 miles), where would you keep your hands, feet, how quickly would you be able to react from a relaxed position, if needed? I think it would be as tiring as driving if driver wants to stay ready to intervene, so what is the point. If driver wants to use that time to sleep, then it's much safer to do it at the back, in a horizontal position, perhaps in a safe chair to be invented. I don't ever use cruise control. People who do keep their right foot on the floor. In emergency it would take at least a second to move it to the brake or gas pedal, it's unacceptably long time of reaction at highway speeds.
@mahonj, "Why did they stop at 48V, why not go to 60V ?" Actually nominal 48V is as close to 60V as they can get, taking into account safety margins never to exceed 60V in any case of overvoltage at any operating temperature. When only lead-acid batteries were available, at the end of 1990s, the auto industry proposed 42V system. Those batteries had wider voltage fluctuations, so 42V was selected - See Wiki 42V system https://en.wikipedia.org/wiki/42-volt_electrical_system. It says: "The limiting factor for direct voltages is a shock-hazard protection limit of 60 V, which must not be exceeded even during voltage fluctuations caused by extreme conditions. This limit eliminates the option of an automotive electrical system with a nominal battery voltage of 48 V, because at low temperatures the charging voltage of the battery can attain 60 V. Also, the price, weight and volume of batteries are influenced by the number of cells, which must therefore be kept to a minimum." Specification LV148 defines voltage levels for 48V system: 36V-52V - Standard Operation; Full components performance 52V-54V - Upper Limited Operation Range (Regen braking peak, Calibration) 54V-58.5V - Overvoltage Range; Overvoltage countermeasures to be activated 58.5V-60V - Safety Reserve IMO it would make sense to have a PHEV 48V for cars that spent too much time in stop-n-go traffic, especially in areas where AC is used for many months of the year. Add the ability to precondition the car. Use 1kWh to 2 kWh battery. Single motor power is usually 5 kW continuous, and up to 12kW (or even 15kW) short peak power. But they can use 2 e-motors, with double power. Such cars should be equipped w/ electric AC, and 48V electric powertrain should have at least two gears, so it can provide good performance moving cars in electric only mode up to 30 or 40kph. Lighter cars would benefit more from this system. The main advantage of 48V system is said to be price - anything below 60V DC is considered Low Voltage, no safety measures needed.
I heard from some Germans I used to work with that US 'stole' all their intellectual property (patents, trademarks, and technologies) and the best scientists (like Wernher von Braun), after the war. Also they don't like the fact that there are still over 50,000 US troops there, while Russian troops went home around year 1990. It could be that Germans said "Who cares if our cars poison Americans, they owe us a lot anyway". US military personnel there is exempt from criminal responsibility, German law does not apply to them, they can do whatever they want, as in most other countries with US bases, there are inter-government agreements that specify it. So US troops can just kidnap Ms Winterkorn (or entire VW board), bring them to USA for justice, before they try to flee to Russia or China (or elsewhere).
@Vupilla, Thanks for the answers. From the patent text (mentioned above) it wasn't clear to me if both e-motors can participate in all electric mode (in Prius only MG2 can do it). Unfortunately I cannot help you sell the invention to a carmaker, but I wish you success in selling/licencing it. Usually in most US patent texts there is significantly more description how system works, and also advantages of the proposed solution. In the texts from the links from your latest email, there is not enough text to conclude how exactly it works, how it handles various scenarios (say high speed, uphill low speed, acceleration, braking, all electric drive). Planetary systems have non linear relations, a lot depends of selected gear ratios, image itself usually is not enough. Mentioned peak motor(s) power of 17 KW is somewhat above peak power that 48 Volt provide, that I saw. Highest I saw was 15 KW peak, below 7 KW continuous. I think it was a Continental system. Limitations are due to cable thickness. You are trying to minimize battery size. With expected battery prices going down in years to come, you may need to reconsider the optimal values for battery size, and motor power too, so it can either be powered by 48 Volt, if not increase its power to better satisfy other design goal (every design is a result of various compromises, total system price is very important ). BTW do you have any details on Renault hybrid system, announced near the end of 2014, a 3 speed system?
@Vupilla, I went to the link you posted, a hybrid drivetrain system. Actually it is US patent 8845469, went there too to get more info. I guess you are familiar with details of the invention (Perhaps the inventor homself?), and I have some questions. Given the example in patent description, 1000 kg car, Thermal Engine: 53 KW at 4000 rpm, 1000-5000 rpm, Electric motor and generator: 17 KW, 0-7000 rpm, 70 mN, 400V\ Battery: 0.5 KWh+0.2 KWh capacitor.. 1. All electric driving: if you have 2 e-mootors of 2x 17 KW (as above), how much max power can they deliver to the wheels when ICE is turned off? 2. These 17 kW for motors - is it continuous power or peak power? 3. When braking from 50 kph to zero (using brake pedal), at what speed will the ICE be turned off? 4. Max electric braking power - with ICE on and with ICE off? 5. How are capacitor and battery connected - in parallel, via a DC-DC converter or some other way? 6. Compared with Prius and Chevy Volt 2016 hybrid systems (or new GM HEV in Malibu, ie without big battery), what are the advantages od this system?
@T2, It was not my claim (80 ms sync time in that video). I just passed the link, and posted a few lines of text from there. They have commercial product, so it works, the numbers may not be quite as good as in video. They may not do it in 80 ms, considering they have torque fill from another motor during shift, so the complete shift can be done a little slower (say within 0.7 sec, it's not a racing car). Please note high ratio L/D on the motor in picture (being held in hands). It's extremely beneficial to have high L/D for low rotor angular inertia, as moment of inertia is proportional to R^2. When I said "Do you think", I expected an educated guess from a very knowledgeable person with lots of hands-on experience, not a definitive answer. I just made a calculation of angular kinetic energy of a hypothetical rotor, weighing 5 kg, L/D=5 (D=2R), at 21,000 rpm. Assumed density = 8,000 kg/m^3 (little above iron, lower than copper - and it's laminated). Found rotor was R=2.7 cm (D=5.4 cm), L=27 cm. Moment of inertia, I=(1/2) m R^2 = 1.8225 x 10^-3 (All SI units) Angular kinetic energy, E=(1/2) I (omega)^2 At 21,000 rpm, the rotor has kinetic energy of 4.414 KJ. To accelerate it to that rpm (or to brake it), in 0.1 sec, power of 44.14 kW needs to be applied. (This is 100% of power, not 75%, for 1/2 of max speed) So their numbers seem very feasible. Unless I made some mistake somewhere. I probably assumed too small rotor, but their motor has 250 HP, so it can handle 50% larger diameter of rotor (with about 4x kinetic energy of this from my example). The reason I assumed just 2 poles, is because of high L/D needed to slowdown/accelerate rotor faster (for multi-speed systems). Also hysteresis loses are probably lower with lower max frequency. In a small diameter you cannot put too many poles. What you found in catalogs are probably not high performance motors, for cost reasons they may have used the same stator.
@T2, agree that 2 downsized motors would be easier to cool (agree on number 26% too, played with formulas myself, after reading your comment earlier). On the other hand using 2 smaller motors opens opportunity of two (or more) speed gearboxes, where one motor provides infill torque (IM with high overload capability well suited for this), while the other motor changes gear using just a dog clutch, after first quickly matching speed of two spinning surfaces to be clutched. For both motors it is desirable to have high overload capability during the shift. For the one driving the wheels - in order to provide infill torque. For the other motor (doing gear shift) - to change its speed (up or down, depending if it is downshifting or upshifting) as fast as possible. Actually WrightSpeed does it already in commercial products (www.WrightSpeed.com). Here is fast shift demonstration : http://www.wrightspeed.com/technology/ 1. Motor is accelerated to 20,700 rpm in first gear, Upshift (Shift from 1st gear to 2nd gear) 2. Motor torque is reduced to zero 3. Shift actuator is moved to neutral position (mid-stroke) 4. Motor speed is synchronized to the correct speed for second gear, 9000 rpm (80 ms) 5. Shift actuator moves to second gear .... One thing here is not clear - what is the phase frequency at mentioned 20,700 rpm (350 Hz if one pair of poles, or 700 Hz if two pair of poles per phase). Some companies bought those trucks, so somebody could answer this question by measuring frequency of current going through cables from inverter into motor, relatively easy (while truck moves, or with wheels lifted, just measure highest frequency), without disconnecting cables to motor. Do you think it would be significantly easier to temporary overload (for gear shift) the induction motor at 350 Hz (21,000 rpm) than at 700 Hz (ie 2 pair of poles, at the same 21,000 rpm)? The torque fill in WrightSpeed truck system is obviously done by, say, left pair of rear wheels while right wheel pair motor shifts, and then the other way around. Similar thing could be done with 4WD e-drives (separate motors on front and rear axles as in some Teslas, model S). On one or on both axles motor can use 2-speed transmission, where motor on the opposite axle provides torque fill while the other does gear change.