Valence Technology, a developer of large-format Lithium-ion rechargeable batteries, and EnergyCS, a developer of integration control systems, are introducing a plug-in hybrid (PHEV) concept car based on a 2004 Toyota Prius.
To be shown at the 21st Worldwide International Battery, Hybrid and Fuel Cell Electric Vehicle Symposium & Exhibition (EVS 21) in Monaco next week, the PHEV uses Valence’s phosphate-based Lithium-ion battery system.
As designed and programmed, the Prius has a driver-selectable EV (electric vehicle) drive mode. When toggled, EV mode turns off the combustion engine and the Prius functions as an all electric vehicle—particularly good for starting up and neighborhood travel. The default EV driving mode can be used for about one mile with a maximum speed of about 34 mph. EV mode is not currently activated for Priuses bound for the US, although it is on models in Japan and Asia.
In its stock EV mode, however, the Prius is not very satisfying. The battery pack wasn’t selected with extended EV operation in mind, and, more critically, the vehicle can’t plug in to recharge the batteries. Staying far away from a plug-in was part of Toyota’s planning, and remains part of the marketing for the car. Toyota took special care especially during the roll out of this version of the Prius to point out that it did NOT plug in.
The California Cars Initiative (CalCars), a non-profit startup dedicated to jump-starting the market for plug-in hybrids (PHEV), has also been working on building a prototype Prius (the Prius+) capable of functioning as a plug-in hybrid and running in full EV (electric vehicle) mode for longer distances than possible with the original Toyota equipment. (Earlier post.)
With a more capable battery pack extending EV operation of the car, the Valence/EnergyCS prototype delivers up to 180 mpg for an average commute of 50–60 miles per day. The vehicle will also be part of the Monte-Carlo Fuel Cell & Hybrid Rallye on April 2.
The Valence batteries use a phosphate-based cathode material rather than the cobalt-oxide used in traditional Li-ion cells. Phosphates are stable in overcharge or short circuit conditions and have the ability to withstand high temperatures without decomposing. When abuse does occur, phosphates are not prone to thermal runaway and will not burn.
In addition to being more stable and safer, the the phosphate-based batteries offer better longevity and discharge than their cobalt-oxide counterparts.