Electric vehicle
Download 3.49 Mb. View original pdf
|
| 49 LOAD Cl − + − 2Na → 2Na + + 2Cl − + 2e − → 2NaCl NiCl 2 → Ni 2 + + 2Cl − + 2e − → Ni Figure 3.10 The reactions at each electrode of the sodium metal chloride battery during discharge Table 3.5 Nominal battery parameters for sodium metal chloride (Zebra) batteries Specific energy Wh kg −1 Energy density Wh l −1 Specific power W kg −1 Nominal cell voltage V average (2.5 V when fully charged) Amphour efficiency Very high Internal resistance Very low, but higher at low levels of charge Commercially available Available commercially, but very few suppliers Operating temperature 300–350 ◦ C Self-discharge When not in use energy must be continually used to keep the battery up to temperature, corresponding to a self-discharge of about 10% per day Number of life cycles >1000 Recharge time h Figure 3.11 A commercial Zebra battery fitted neatly under the seat of an experimental battery electric vehicle by MES-DEA. The battery stores about 18 kWh of electrical energy 50 Electric Vehicle Technology Explained, Second Edition of energy. However, when not in use it consumes about 100 W of power keeping up to temperature. So, in a 24 hour period the heating will require 0 .1 × 24 = 2.4 kWh of energy, corresponding to about 13% of the stored energy. In energy terms, this corresponds to the self-discharge of other types of battery, and is quite a high figure. Zebra batteries can be allowed to cool, but if this happens they must be reheated slowly and steadily, a process typically taking about 24 hours. They are available as tried and tested units with well-established performance criteria, though only in a very limited range of size. An example is shown in Figure The overall characteristics of the battery are given in Table 3.5. These are taken from the kWh ( ∼280 V, 64 Ah, 180 kg, 32 kW peak power) unit manufactured by MES-DEA of Switzerland. Download 3.49 Mb. Share with your friends:
|