We were having fun at the Bracken Ridge Tavern in Brisbane, Queensland, for our regular “Electric Vehicle Coffee, Cake, and EVs” gathering. When Brian, a newcomer to the group, told us a tale about hitting a kangaroo while driving from Winton to Charters Towers in north central Queensland, it caught my interest. Then he revealed that his car was a Toyota Prius. Now, I was genuinely curious. He was able to respond to some of my inquiries on why Toyota didn’t switch from the Prius hybrid electric car to battery electric vehicles and to describe the differences between driving the Prius and his new Hyundai Ioniq BEV because he is an engineer. He said the following to me:
An engineer would have found the initial Prius development to be fascinating, especially the relationship between the engineering and the business strategy. Toyota provided the concept to a board member who was an excellent engineer and told him to do whatever he wanted – development funding was not a concern! There were three key components that needed to be addressed separately before combining in the best way:
Batteries and battery management systems, first (BMS). Since batteries were outside of Toyota’s expertise, they contracted with Panasonic to serve as the main producer of nickel-metal hydride (NiMH) batteries. The logistics of raw materials were not likely to be a barrier at the time because this chemical represented the “state of the art” in battery chemistries. But since batteries were only expected to last 200–300 cycles, a BMS had to be created to significantly increase this. Breaking the battery down into a lot of smaller modules and using computer control to make sure that the usual operating state of charge stayed within the range of 30% to 80% was the technique utilized to improve battery life. No battery module was permitted to be totally discharged or overcharged, in other words.
2. Transmittal. This needed to complementarily blend the qualities of electric and internal combustion engine (ICE) devices. Over a limited speed range, the ICE motor produces high energy and torque. The electric motor allows energy to be recovered during braking and placed back into the battery, which lowers overall energy consumption while providing maximum torque at zero speed (perfect for quick takeoff). The electronic continuously variable gearbox was the Toyota response (eCVT). Since it is the only CVT without sliding components, it is special in that its lifespan is comparable to that of a fixed ratio gearbox. Toyota secured this via patents, forcing rival manufacturers to come up with alternative (less efficient) solutions to the transmission issue. This gave Toyota a significant competitive edge. The eCVT, or electronic continuously variable transmission, was a fixed ratio gearbox with one input from the internal combustion engine (ICE), one input/output from the electric motor/generator, and one output/input connected to the wheel (s). In order to maximize performance, the direction and ratios of energy flow were continuously controlled by computer.
ICE Motor 3. The Otto thermodynamic cycle , which has the broadest practical operating speed range, is used by pure ICE automobiles. The Atkinson cycle is typically used in hybrid vehicles; while it is far more effective, it has a much smaller operating speed range. Toyota optimized the sizes and power-to-weight ratios of the three main components in the original Prius, making it the most effective people mover on the road. The battery has a meager amount of “battery only” range—barely enough to support regenerative braking and starting torque. It was also unable to operate in ICE-only mode (as I found to my chagrin when the battery eventually died and the car was donated to a training college).
I believe that this became the Prius’ Achilles heel because it was unable to efficiently develop into a plug-in hybrid electric vehicle when technology permitted it to do so (PHEV). Toyota claimed that the second Prius model was the first to turn a profit after the first Prius model was sold at a loss. The eCVT, power electronics, and computer systems that made up the “Hybrid Synergy Drive” were easily adaptable to various car models (Corolla, Camry, RAV4, etc.), allowing for profit taking with little further research.
Toyota putting all of its eggs in the hybrid basket, so when lithium battery technology eventually made the BEV the best option, Toyota had no advantage over the competition. Pure EVs have far larger useful regenerative energy range and beginning torque that is much better matched to requirements. (I noted the latter in especially on the way back from Toowoomba down the range; the Prius would quickly approach 100% battery capacity, necessitating friction braking for the majority of the run. The Ioniq battery always has plenty of space.)
The features of the BEV that I appreciate the most from an engineer’s perspective are:
There are none. I pay more for exclusively renewable power when I charge at home (so the trolls cannot accuse me of using any coal-fired power). In 1965, I first learned about the issues caused by CO2 emissions. simplicity, elegance, and the absence of moving parts in the design Low maintenance costs result from this. I probably won’t need to change the brake pads over the car’s lifetime because I just use one pedal. (However, in the Prius, I only replaced them once every 400,000 kilometers.) efficient use of energy. I actually spend more money on coffee than I do on energy during long trips! maximum torque when moving at rest. At a congested roundabout, the EV maneuvers into areas that an ICE vehicle would not be able to enter, even in ECO mode. Contrary to ICE, stop-and-start driving on the Bruce Highway during busy peak hours consumes very little energy. Toyota provided the 1993 Prius shown in this post.
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