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Toyota beginning on-road testing of new SiC power semiconductor technology; hybrid Camry and fuel cell bus

SiC PCU under the hood of the Camry hybrid test vehicle. Click to enlarge.

Toyota will begin the on-road testing of silicon carbide (SiC) power semiconductors in Japan this year, using a Camry hybrid prototype and a fuel cell bus. The tests will evaluate the performance of the SiC technology, which could lead to significant efficiency improvements in hybrids and other electric-drive vehicles. (Earlier post.)

Power semiconductors are found in power control units (PCUs), which are used to control motor drive power in hybrids and other vehicles with electric powertrains. PCUs play a crucial role in the use of electricity, supplying battery power to the motors during operation and recharging the battery using energy recovered during deceleration. At present, power semiconductors account for approximately 20% of a vehicle’s total electrical losses; raising the efficiency of the power semiconductors is a promising way to increase powertrain efficiency.

SiC PCU. Click to enlarge.

Compared to silicon, SiC power semiconductors lose 1/10 the power and drive frequency can be increased by a factor of ten. This enables the coil and capacitor, which account for approximately 40% of the size of the PCU, to be reduced in size. Through use of SiC power semiconductors, Toyota aims to improve hybrid vehicle (HV) fuel efficiency by 10% under the Japanese Ministry of Land, Infrastructure, Transport and Tourism’s (MLIT) JC08 test cycle and reduce PCU size by 80% compared to current PCUs with silicon-only power semiconductors.

The technologies behind these SiC power semiconductors were developed jointly by Toyota, Denso Corporation, and Toyota Central R&D Labs., Inc. as part of the results of a broader R&D project in Japan (the R&D Partnership for Future Power Electronics Technology under consignment from the New Energy and Industrial Technology Development Organization). The three had announced their joint development efforts in May 2014.

In the Camry hybrid prototype, Toyota is installing SiC power semiconductors (transistors and diodes) in the PCU’s internal voltage step-up converter and the inverter that controls the motor. Data gathered will include PCU voltage and current as well as driving speeds, driving patterns, and conditions such as outside temperature.

By comparing this information with data from silicon semiconductors currently in use, Toyota will assess the improvement to efficiency achieved by the new SiC power semiconductors. Road testing of the Camry prototype will begin (primarily in Toyota City) in early February 2015, and will continue for about one year.

Brief presentation on Toyota’s newly developed silicon carbide (SiC) power semiconductor for use in automotive power control units from the May 2014 announcement. Click to enlarge.

Similarly, on 9 January, Toyota began collecting operating data from a fuel cell bus currently in regular commercial operation in Toyota City. The bus features SiC diodes in the fuel cell voltage step-up converter, which is used to control the voltage of electricity from the fuel cell stack.

Data from testing will be reflected in development, with the goal of putting the new SiC power semiconductors into practical use as soon as possible.

Camry SiC-equipped test vehicle. Click to enlarge.


Roger Pham

Continued from above:
"Researchers in Argonne's Center for Transportation Research have developed advanced combustion concepts for hydrogen internal combustion engines to meet the U.S. Department of Energy challenging goals, which include a peak brake thermal efficiency of 45.5% and drive-cycle NOx emissions as low as 0.07 g/mile."

By comparison, current Prius' Atkinson-cycle engine now can achieve 38% peak efficiency. 45.5 / 38 = 1.2 improvement.
Source: http://www.transportation.anl.gov/engines/efficiency_goals_h2_combust_engine.html


Technology changes to reduce total vehicle weight are welcomed. If they improve performance and cost at the same time, it is a win-win-win addition.

Panasonic-Tesla should be praised to have found ways to package enough lower cost batteries to support extended EV range without restricting passenger space. One day, all others will copy and use high capacity (120 to 150 kWh) under floor battery pack good for 500+ miles.


Ah Roger, still humping the leg of any hydrogen based article you can find...even after all these years LOL

Roger Pham


Funny, isn't it,that this article is about SiC power controller for e-motor, yet it can improve efficiency of HEV enough that future HEV's may well run on Hydrogen...or Natural gas stored in the same tank and flow thru the same gaseous direct injector.

Running on Nat Gas, only 3,600 psi is needed for 300-mi range and not necessary to pump it up to 10,000 psi in the case of Hydrogen. You can "charge" it up at home, using the equivalent of the Phill as you would charge up a BEV.

World-wide, there are already 19 millions CNG vehicles. Making a CNG vehicle that can run on H2 is a big plus. Large-volume production will make these affordable.

Since the Mirai has two H2 tanks, making one H2/CNG tank capable of being filled up also with gasoline, and adding another gasoline port injector to each cylinder would make the car tri-fuel-capable: CNG, H2 and Petrol.
So, you can fill up your future tri-fuel HEV with renewable-energy H2 in your home town, out of environmental concern, and, when going out of town, you will settle for gasoline during the trip where H2 will still not be available.

Voila, coast-to-coast travel on an H2-capable car without H2 infrastructure problem!


Sorry if this is a bit off topic, but what is the highest amperage 240V home charger they make?

or if they have a 480V three phase setup available for the home?(pretty sure this Voltage isn't available to me, but it would be a good investment if batteries were @ $180kwH)

To me, that charging time would make or break the setup


According to some posts above, battery prices for BEVs are $400/kWh, going down thanks to economy of scale. Battery prices for PHEVs per kWh are expected to be (significantly) higher, as they need to be of higher power (kW/kg).
Average BEV (24-85 kWh) uses much more batteries than average PHEV (6-16 kwh). So economy of scale will bring down the price of batteries for BEVs much quicker than batteries for PHEVs. It will cause even larger price disadvantage for PHEV batteries in the future.

It would be very desirable to have PHEVs use BEVs batteries. It is feasible if an ultracapacitor module would be added between battery module and e-motor. An extra inverter would be needed between battery bank and ultracap bank, with lower power rating (for average power) than the inverter between ultracap bank and e-motor (for peak power).
So for PHEVs the critical element is suitable ultracapacitor, reasonably priced. Some 200-250 Wh of energy capacity (with sufficient power) would be needed for a passenger car.
Currently available ultracaps have about 5Wh/kg, and somebody here on GCC mentioned price of 15,000/kWh.
What's needed for PHEVs is ultracaps that cost no more than $6,000/kWh, and have energy density of at least 12 or 15 Wh/kg.
Once such energy density ultracaps become available (with sufficient power density), economy of scale (for PHEVs using batteries for BEVs) will bring their price down.
On the other hand this architecture (extra inverter and ultracap bank) would mean more modules than can fail. Benefit would be lower price, less needed space for batteries (BEV batts have higher energy density). Ultracap module, if small, could be placed in engine area, and be connected to battery with thinner cables (for average power).

Inverter prices are reportedly around $10/kW.

Roger Pham

@Alex C,

I have good news for you. Tesla's battery, 18650 NCA, has been tested by independent laboratory at Penn State University to be capable of 5-C with repeat charging and discharging cycles ad nauseum. The Tesla Model S P85D puts out nearly 700 hp, or about 520 kW. Divide this 520 by 85 kWh pack and one gets 6-C discharge rate.

Let's say a PHEV is equipped with a 15-kWh Tesla's battery pack that is good for about 40 mile of range. Let's use only 4-C max discharge to conserve battery life. Multiply 15-kWh by 4-C will give us 60 kW of power, enough for spirited acceleration with a CVT (transmission). A PHEV version will have a 90 kW engine, preferrably 1-liter turbocharged or 1.5 liter non turbocharged, and a CVT transmission lifted off current Corolla or Sentra. Behind a CVT, 60 kW of e-power will give a lot of acceleration in comparison to without transmission. Combined power will be about 150 kW of power, or 201 hp, which is quite fast for a 3,000-lb plus PHEV, like the Tesla Model S PHEV version with 15 kWh of battery. Reduction of e-motor power will save money, since e-power costs about $60 per hp, while conserving battery life, for a PHEV. Reduction of battery capacity from 85-kWh to 15 kWh will save about $28,000 in cost, with current battery priced at $400 per kwh. The reduction in e-power from 360 hp of current Model S down to 80 hp will save about 280 hp x $60 = $16,800. Allocating ~$6,800 for the engine and CVT, and one would save about ~$38,000 vs. Model S 85-kWh version. Base price for Model S 85 is now $80k. Substracting $38,000 will give $42,000 as base price for the Model S 15-kWh PHEV. Not quite down to the $35,000 projected price for the Model 3, however model S is bigger and will save substantially on capital cost of developing Model 3 (billions of $$$) and billions $$$ more capital expenditure can be saved from the Giga battery factory.

THose wanting more power can opt for a bigger battery pack, like a 20-kWh pack (the Volt 2 already has a 18.5 kWh pack) and 6-C discharge, or 120 kWh of e-power. Mated with a 120-kW engine, 1.5 liter turbocharged, for a total of 240 kW, or 322 hp for a 3,500-lb car, and this will fetch sport-luxury-model pricing of well above $50,000.

What are you waiting for Mr. Musk? And why are you putting all the eggs in one basket, as Mr. Bob Carter of Toyota wondered?


Thanks for the reply.
Tesla's battery, 18650 NCA may be capable of 5-C discharge rate.
I think carmakers do more rigorous battery testing than some third parties who have little to lose if they fail to take into account all possible scenarios, that can cost dearly the carmakers.
For example BEV Nissan Leaf batteries have 3.54-C discharge rate (85 kW/24 kWh). PHEV Chevy Volt has 6.85-C (110 kW / 16 kWh). Honda Accord PHEV 18.5-C (124 kW/6.7 kWh), on condition motor car develop full power without the help of generator, but very high 'C' rate anyway.
One thing I overlooked when assumed the use of BEV batteries for PHEVs (w/ultracap bank), is cycle life, which is apparently lower for BEVs as they do not travel every day max distance (i.e. not fully charged daily), while PHEV's usually do. Perhaps some future batteries for BEV's will have 3,000+ life cycle.

I like your PHEV with 15 kWh, but highly unlikely Tesla would consider any PHEV in near future. Even slight chance for an EREV, like BMV i3. Two reasons. First it would go against their philosophy, they make pure EV cars. Another thing is who would supply the best performing ICE's for them, being direct competitor to major brands.

BTW do you know how long the H2 will stay in those tanks used in FCell cars, ie is there some sort of "self discharge rate", as H2 tends to escape through most materials. How long does it take for the initial quantity of H2 to drop to 1/2 - days, weeks or months?

Re: "since e-power costs about $60 per hp,"
I think it's quite lower than that.
Did you try to call spare parts depts and ask for price of e-motors for (P)HEVs and BEVs?
Then deduct a common margin for parts, to get close to the price they pay for the e-motors?
It is possible to get prices that way from dealers, except for Mitsubishi (UK and Australia), where they cannot tell you price for any of 3 motors in Outlander PHEV unless you provide a VIN. Nissan dealers also ask for VIN, but some of them tell price without VIN.
I found Prius gearbox very expensive, some $5,000 a few years back, without e-motors.

Roger Pham

@Alex C,

Penn State University tested the 18650 NCA batteries at 5C charging and discharging, continously, and found 80% remaining capacity after 5,000 cycles. Of course, real-life cycle life will be less due to aging effect, owners kept batteries fully charged or nearly-drained, and high-temp effect in the summers not accounted for in the laboratory with optimal cooling.

>>>>"Another thing is who would supply the best performing ICE's for them, being direct competitor to major brands."

Answer: Yamaha engine division. Yamaha has designed and built among the best in engines for diverse major car companies like Ford, Toyota, Lotus, etc.
Bombardier Rotax and Evinrude is another possibility.
There are also other companies who make engines for motorcycles or off-road vehicles, like Kawasaki, who are not in direct competition with auto companies.

I know, trying to convert Tesla to PHEV's would be like trying to convert someone to a new faith (religion). Very difficult and many missionaries have become martyrs.

I have seen data to the effect that leakage rates in carbon fiber hydrogen fuel tank are negligible. CAN'T quite recall the exact numbers, but may be around 0.1% after many months.

The cost estimate of $60 for e-power including power controller is with profit included, for retail customers. It was done by comparing many different car models with electric version, HEV version vs ICEV version, and retail prices of many e-motors for both EV and non-EV application, plus retail pricing for power controller per kW.
Try it, and you'll find a consistent number of $50 per kw for e-motor and $10 for e-controller, for EV motors and non-EV motors alike. One easy example would be Tesla 200-HP motor upgrade from model S P85 to 85D of $10,600.
The cost before profit is difficult to obtain and difficult to prove.

>>>"I found Prius gearbox very expensive, some $5,000 a few years back, without e-motors."
Don't buy new parts from dealers, because the markups will be very high. Instead, go to custom repair shops who have a habit of salvaging parts from junkyard, or buy them new or used from e-bay.

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