The ZEBRA Battery

The operation of the battery is controlled by a battery controller, which is the brain of the battery and ensures that the battery always stays within the operating hmits. 

The performance of the ZEBRA battery system is shown in Table 21.3. 

The battery system has reached more than 1700 cycles in hfe cycle tests. The calendar life of the zebra battery has been proven to be close to five years in a continuing life test. In practical operation in cars the ZEBRA battery exceeded 110000km within a three year period. This excellent result proves the ZEBRA battery to be a reliable system. 

The ZEBRA cells are connected in series to obtain the demanded voltages, and chains of these cells are connected in parallel to obtain the capacity which is requested. At present there is a request from the car companies to obtain battery voltages close to 300 V, which means that about 110-120 cells will be connected in series in one string. The capacity of one 

The operation of the battery is controlled by a battery controller, which is the 

There are some other advantageous properties to be mentioned the nameplate capacity of a battery can be fully discharged. 

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Recently the development of Na/S batteries for car applications has been abandoned only Na/S batteries for stationary applications (load leveling) are still under development in Japan. Among the high-temperature batteries, the ZEBRA battery is the only system at present which is being commercialized for car applications. 

Because of the less advanced status of the lithium aluminum/iron sulfide battery, only the ZEBRA battery and the Na/S battery are described in this section. 

The ZEBRA battery is a high-energy battery based on a cell with electrodes of sodium and metal chloride. The ZEBRA system was first described by Coetzer in 1986 12J. 

The safety of the ZEBRA battery has been proven extensively by abuse testing overheating, overcharging, short-circuiting of battery terminals and of cell groups, crash tests on the battery itself by dropping it at 50 km h 1 onto a pole or spike, and crash tests of cars with built-in ZEBRA batteries at 50 kmh-1 [10]. The results of abuse testing prove the ZEBRA battery to be a safe battery system. 

Currently interest has now been directed toward a similar high temperature system, the ZEBRA Battery, which also uses P-alumina as a Na ion conductor. The sulfur electrode is replaced by nickel chloride or by a mixture of ferrous and nickel chlorides. Contact between the NiCl2 electrode and the solid electrolyte is poor as they are both solids, and current flow is improved by adding a second liquid electrolyte (molten NaAlCb) between this electrode and the P-alumina. The overall cell reaction is now ... 

The Zebra battery is presently at the pilot line production stage. About 170 batteries are on test, mostly in vehicles but some on bench tests. The batteries are installed in passenger cars and in buses, and in the German electric vehicle fleet test on the island of Rugen, 52% of the 60 or so vehicles are equipped with Zebra batteries. A lifetime of 4 years, 1260... 

Fig. 4.25 Ragone plot comparing the internal combustion engine with the ZEBRA battery and fuel cells (very approximate). [The plot was introduced for comparing batteries (standardized to a weight of 300 kg) to include the performances of engines and fuel cells in a meaningful way their masses, together with the fuel carried, should be standardized to 300 kg.].

In the series hybrid vehicle a ZEBRA battery would complement the internal combustion engine. This combination could offer pollution-free motoring within cities, with the more powerful but dirty petrol/diesel motive power used for longer journeys. In the 100 kW h to 10 MW h energy range the batteries would be suited to load-levelling. The ZEBRA battery is now being mass-produced (MES-DEA, Stabio, Italy). 

Such a battery was proposed for the first time by Yu et al. [475] and by Gray et al. [470], These batteries utilize the same pair of electrodes as the Zebra battery, Na/FeCl2, but the electrolyte is a room temperature molten salt, A1C13-MEIC-NaCl. Yu et al. [475] used this electrolyte with the following composition 47 45 8 mole%. Gray et al. [470] proposed the addition of HC1 to the electrolyte. The electrode reactions during discharge are... 

In order to keep the Zebra batteries at the high temperature required for their operahon, they need to be kept connected to the electric network when they are not in use. This represents a limitation of their application, and makes them more suitable specihcally for public transportation means, rather than small private vehicles. 

C.-H. Dustman, Latest Advancement on the ZEBRA Battery, presented at the DOE Ad Hoc Advanced Battery Readiness Working Group, March 4-5,1998. 

Battery safety is so important for mobile and vehicle apphcations. Especially for vehicles, on the road, accident likely becomes heavy, and the crash accident should not bring more danger by release of the energy stored in the cells. And various tests are usually conducted. In ZEBRA battery case, test results were reported. Crash of an operative battery against a pole with 50 km/h, overcharge test, overdischarge test, short circuit test, vibration test, external fire test, and submersion of the battery in water have been specified and performed [6]. The ZEBRA battery did pass all these tests owing to its four-barrier safety concept [7, 8] chemical aspects, cell case, thermal structure, and battery controller. 

Africa)io is a variant of sodium-sulfur technology where sulfur is replaced with a metal chloride such as NiCl2 (nickel chloride) or FeCU. It was specifically developed for applications in electric vehicles, freight transport and public transport the ZEBRA battery is more particularly intended to serve buses and utility vehicles. As with the Na-S battery, the vibrations felt in a vehicle may cause premature aging of the ceramic/metal interface. Today, such batteries are also being considered for stationary applications. 

The ZEBRA battery comprises a NiCU positive electrode in a central compartment with NaCl salt, impregnated with NaAlCls, which is a liquid mixture of NaCl and AICI3 (considered to be a secondary electrolyte). The negative electrode is liquid sodium confined in a second, outer compartment. The wall separating the two compartments is made of a P alumina ceramic (or P-AI2O3), conductive of sodium ions, considered to be the primary electrolyte. The element is sealed hermetically and functions at temperatures equal to or higher than 300°C so that the active components remain in the liquid state. 

The ZEBRA battery system is designed for electric vehicles (Figure 10.12) which require a balance of power to energy of about 2, e.g., a 25 kWh battery has about 50 kW peak power. Other applications are electric vans, buses, and hybrid buses with ZEV range (Figures 10.13 and 10.14). 

These conditions are beginning to be reahstic due to rise of crude oil price and the beginning of series production of at least the ZEBRA battery. Now electric vehicles are starting to become an option for urban traffic, about 100 years after their first period of success. 

The latest ZEBRA batteries contain the cells that have incorporated changes to improve dramatically the battery power and energy (refer to Sec. 4.3.3)." - The physical and performance specifications for a modern battery design are listed in Table 40.8 and a corresponding picture is shown in Fig. AQ.llb. The ZEBRA batteries now meet or exceed all of the mid-term EV requirements of the three major U.S. automakers (specified through the USABC). 

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