Basic Terminology 25 regenerates energy, back into the battery, which then provides power to the vehicle during start and stop events when the engine is turned off. It is important to understand that in the hybrid system the electric power to charge the battery is entirely provided by the on-board generator, the HEV does not plug into the grid to charge the battery ( Figure 3 ). A microhybrid ( μ -HEV) refers to a Stop/Start (S/S)-type system. In this type of hybrid, there is a very small battery, often a lead acid or a very small lithium-ion battery, that powers the vehicle systems when the control system automatically shuts off and then restarts the engine when the vehicle stops.
Most of these systems do not offer support for regenerative braking because the battery is too small to capture the amount of energy that would be regenerated back into it. However, some systems with larger batteries (usually those with >750–1000 Wh) may include regenerative braking capability and on-board power support for electrically powered systems such as power steering, power brakes, entertainment system, HVAC, and vehicle lighting while the engine is stopped. This configuration is gaining much popularity in all regions around the world due to the low cost and general simplicity of this system.
A Neighborhood Electric Vehicle (NEV) is a fully electric vehicle but it is limited to a maxi- mum speed of about 30 mph (up to 45 mph in some areas), must have a gross vehicle weight of less than 3000 pounds, and can be driven only on limited public streets. These limits are based on current US laws and regulations for this type of low-speed vehicle. The NEV is commonly used on college campuses and in small private communities. These vehicles can basically be considered next generation or “souped up” golf carts as that is their basic beginning structure. One important thing to take note of is that this same term has a very different meaning in different regions of the world.
In China, this same term, NEV, is used to describe China’s New Energy Vehicle (NEV) policy. This policy was develop in China based on the “863” program and subsequently the Tenth Five Year Plan, which created a set of incentives and goals for increasing the amount of New Technology Vehicles in an effort to reduce air pollution. This policy was also developed in order to advance Research and Development (R&D) in the areas of HEVs, EVs, and Fuel Cell Vehicles (FCVs) in China. For the purposes of this text the term NEV will be used to represent the Neighborhood Electric Vehicle unless otherwise stated. ^ƚĂƌƟŶŐ ^ Ɵ ĐĐĞůĞƌĂƟŶŐ ĞĐĞůĞƌĂƟŶŐ ^ƚŽƉƉŝŶŐ Figure 3 Operating cycle of hybrid car.