The skeleton of electric car includes important parts such as metal body with wheels, motor and the batteries. The motor can be simple DC Motor to single phase/three phase induction motor. Induction motors are preferred for ruggedness, reliability and maintenance. There is not much innovation in motors except for improving the efficiency and long life. The motor need to be designed for regenerative braking so that it works as generator as well.
The most important thing which can improve the performance of electric car are batteries. Quick charging ability, higher energy density, long storage and wide operating temperature all important. Lithium Ion batteries are the best choice when it comes these parameters. But the risk of Lithium Battery is safety. Battery researchers lately have developed Lithium Ion batteries which does not catch fire with good support of charge and discharge control electronics. There are many electric cars adopting Lithium Ion for EVs. One of successful electric car model S EV from Tesla has used Lithium Ion batteries made by Panasonic. Panasonic has said it has shipped 100 million Lithium Ion Batteries to Tesla for use in its electric car model S EV. With a very comfortable driving range of 500km this car is projected to top 20,000 units sales in 2013.
India's popular electric car maker Mahindra Reva has launched a new model e2o with Lithium batteries. Compared to the old model which has used Lead Acid batteries, Lithium Ion batteries are 3-4 times better than Lead Acid in energy density and are also easy to maintain. The cycle life of Lithium Ion is also better by another 200-300 cycles compared to lead-acid. Reva e2o is priced around Rs. 6,00,000 (US$10500).
To further better the performance of batteries in EVs researchers are trying out Lithium Sulphur batteries with energy densities 3/4 times higher than Lithium Ion. Scientists at Oak Ridge National Laboratory in U.S. have designed and tested solid lithium-sulfur battery with 4x energy density of conventional lithium-ion battery.
The negative thing about Lithium Ion is the cost of the battery, the battery replace for Mahindra Reva e20 after 5 years is said to cost around 1,80,000 Rupees (US$3100). On long term basis still it saves money over petrol car.
Though all these technology innovations making an electric car a better option for those who have big packets but still not enough to motivate an Indian ordinary middle class to buy EV when there is option of Tata Nano which is available at 1/4th price of Mahindra Reva e20.