There is a great deal of media attention surrounding electric cars, which have been sold in limited quantities to selected markets. However, the most successful electric vehicle (EVs) markets are not those with four wheels, but rather those with two wheels, the achievements of which are often forgotten.

In 2011 Pike Research, an American market survey company, published 10 predictions about the EV market, of which number five was: 'The best-selling EVs won't have four wheels.' They predict that electric two-wheelers will sell better than electric cars over a long period. Electric bikes account for 56% of global sales for two-wheeler EVs, whilst electric motorcycles account for 43% and electric scooters for approximately 1%. However, a new and improved repair and sales system must be built up to further increase sales, even beyond Pike Research's predictions.

Global market trends
Currently, the largest market is South Asia, but those that are growing fastest are in the Middle East and Africa, where growth will be 54% annually between 2011 and 2016. However, for 2011 Pike Research has predicted that the total sales of two-wheeled EVs will be 54 million in 2011 in the Asia Pacific region, which accounts for – mainly due to China – 95% of the market. According to researcher Jonathan Weinert of UC Davis, 40,000 electric bikes were sold in China in 1998. By 2005, however, 10 million had been sold, which more than doubled in 2007 to 21 million. This rapid increase has been dependent upon three factors: several Chinese cities stopping the use of ICE motorcycles; an increase of wealth in China; and cheaper electric bikes.

Moreover, the increase will probably continue, with survey data from three major Chinese cities showing that most bicycle users (approximately 450 million) would upgrade to an electric bike when they next replaced their bicycle.

This development of electric bikes has been supported by national policy in China. In 1999, the National Technical Standard specified size and performance, and then in 2004 the National Road Transportation Law classified electric bikes as 'bicycles' – meaning that users do not need any form of driving licence or a helmet, and those riding electric bikes can also use cycle lanes.

The next largest market is Japan, with annual sales of approximately 270,000 (2006), and growth of around 13% per year since 2000. Europe, meanwhile, is a smaller market, with annual sales of approximately 190,000 (2006).

However, both the Japanese and European markets are different from the Chinese one. In Europe and Japan, electric bikes are the 'pedal-assist type', which means that the user typically pedals but is aided by a small electric motor when extra power is needed, for example during acceleration and uphill climbing. These bikes normally use Ni-MH or Li-ion batteries, which have capacity ranges between 0.2-0.6kWh, electric motor range between 150-250W and cost US$700-2,000.

Battery performance
In 2005, approximately 95% of electric bikes in China used valvelectric regulated lead-acid (VRLA) batteries. The price for these batteries has decreased, which explains some of the growth in sales of electric bikes in China. Increasingly, however, electric bikes are using Li-ion batteries, but a total shift from VRLA to Li-ion seems unlikely given the cost premium relative to performance.

A typical electric bike in China costs around US$150-300 and has a range of 30-70km per eight hour charge – although high-range electric bikes with a range of 80km are also available. A commuter with an electric bike usually travels around 9km/day. The VRLA battery weighs approximately 12-26kg, depending on size and use, which is limited by the user's physical strength, as they are often removed in order to be recharged at home. However, it is not uncommon for a user to roll the entire bike into their home to recharge it.

Around 300 Chinese companies specialise in producing VRLA batteries for electric bikes. In 2005, the total Chinese production of VRLA for electric bikes was approximately 3.5-9 million kWh/yr; by 2006, it was probably closer to 15-20 million kWh/year.

Environmental considerations
Electric bikes are an energy-efficient mode of transportation, with zero tailpipe emissions. Their energy use is approximately 2kWh/100km, whilst the most popular electric car, the Nissan LEAF, uses 15-20kWh/100km, depending of driving conditions – so on average an electric bike driver uses 10% of the energy that an electric car driver uses. The overall major problem with electric cars is recharging time and the low range. However, the electric bike has a reasonable range, and it is easier to recharge the battery because it can be removed. Therefore, the need for a public recharging infrastructure is lessened.

However, one of the environmental issues with VRLA is the production of batteries. In China, there have been some problems regulating the Pb-acid battery industry, as companies are small and therefore difficult to control. There are a lot of low-quality batteries entering the market, and there have been problems with toxic materials, such as cadmium. According to Weinert, 23% of Chinese electric bikes companies in 2006 did not pass the minimum quality standards. In addition to this, an environmental assessment published in 2009 concluded that lead emissions are the major environmental reservation associated with electric bikes. Although it is possible to use technologies other than VRLA – such as Li-ion batteries – cost premium remains high.

The number of electric two-wheelers sold will continue to be greater than the number of electric cars. It is easy to overlook the two-wheel EV market, but, in my opinion, they are a useful and energy-efficient mode of transport for cities, and their importance will increase. Several cities around the world support the purchase of electric bikes, which will improve congestion and air pollution. The market for batteries will consequently also increase, as will the demand for low-cost, high-performance batteries. However, a major concern remains in how the increased share of electric bikes will affect traffic safety.