1. power and energy requirments
    1. The power demand, PB , on the battery of an EV is given by: PB = Pv / εM ε E
    2. Implant vehicles
      1. A battery pack is then selected and is designed to have an excess capacity over the calculated value. This ensures that over-discharging does not occur and also accommodates the decline in battery performance with service.
      2. In order to arrive at the total energy demand placed on the battery, the sum of the energy requirements of each run is multiplied by the number of journeys to be accomplished within a given working period.
      3. Note, additional power is needed in lifting operations; this is proportional to the total weight that has to be raised.
      4. In terms of power demand (eqn. (3.1))
      5. Item (i) covers the forces Fr and Fa'
      6. while item (ii) concerns Fh; the remaining force, Fw' is negligible because of the low speeds encountered in this type of service.
      7. This involves an assessment of:
        1. (i) the extent of the journey on the flat;
        2. (ii) the elevation of any ramps to be negotiated;
        3. (iii) the weights of the loads and the heights to which they need to be lifted.
      8. To utilize this information, operators analyze their duty profiles in terms of the kind and amount of work that has to be accomplished.
      9. For example, electric trucks employed in materials handling carry out specific routines of lifting and moving loads within working shifts. In such an application, it is possible to calculate with reasonable accuracy, the energy which is required for the given task.
      10. Vehicle manufacturers provide customers with data which quantify the energy demanded from the battery in performing the individual vehicle maneuvers typically associated with materials handling.
      11. The duty profiles of in-plant EVs are usually regular and well-defined.
    3. Road vehicles
      1. Lead/acid batteries have proved to be quite adequate for powering on-the-road EVs in situations where the distances to be covered in the duty profiles are relatively short.
      2. The most longstanding and successful of these applications has been the doorstep delivery of milk in the UK.
      3. Battery-powered delivery vans have also found useful markets.
      4. An effective measure of EV performance is the energy consumed in moving the vehicle over unit distance. Since three of the four forces which resist propulsion are linearly dependent on the mass of the vehicle (see eqns. (3.1) to (3.6) the energy demand on the battery is approximately proportional to this mass.
      5. Therefore, the energy per tonne per kilometre (Wh t-1 km-1) is an appropriate measure of the performance of different vehicles. This parameter depends on the driving profile since the resistive forces are a function of velocity and acceleration (eqns. (3.2)-(3.6).
      6. For example, the greater energy consumption of a milk float compared with a van (Table 3.1) is due to the multiple stop-start nature of the former's service.
      7. In order to explore the ability of batteries to power EVs in a wide spectrum of applications, it is necessary to define a duty profile which is representative of general driving behaviour.
      8. Each vehicle owner has different transportation needs, although most of the trips would be expected to follow a regular pattern, e.g., daily commuting by the private motorist.
      9. Further, most driving will be undertaken in urban/suburban locations and therefore each driver will, in general, face similar road conditions and carry out similar manoeuvres, e.g., acceleration, cruising, braking, stopping at traffic lights.
      10. Standard driving schedules have been developed that represent typical vehicle service.
  2. Characteristics required for an ideal EV battery
    1. To provide affordable road EV s with acceptable performance in mixed traffic, the motive-power batteries must have the following characteristics:
    2. high energy per unit mass/volume ~ for long driving range
    3. high peak power ~ for good acceleration and hill-climbing
    4. high energy efficiency ~ for economic use of input electricity
    5. low self-discharge ~ to minimize energy loss on standing
    6. fast recharge ~ for rapid refuelling
    7. long service (cycle) life ~ for low depreciation cost
    8. low cost ~ to gain customer acceptance
    9. zero (or low) maintenance ~ so that little routine attention is required
    10. independent of ambient conditions ~ resistant to both extremes and variations in local climate
    11. robust design and operation ~ tolerant of abuse (both electrical and mechanical)
    12. environmentally benign ~ non-toxic materials
    13. proven safety ~ safe to use under both normal driving and crash conditions
    14. readily available constituents ~ made from non-strategic materials.
    15. Among these requirements, the key feature of an EV battery is its specific energy, closely followed by specific power, cycle life, and cost.