Reserve Battery

Less critical measurements in everyday laboratory or industrial work are made with the unsaturated Weston cell in which no crystals of CdS048/3H20 are used and the saturated CdS04 solution is replaced by a lower-concentration solution (saturated at 4°C). The OCV of this cell is 1.0192 0.0002 V, that is, its reproducibility is lower. As the solution concentration does not vary with temperature, in contrast to the saturated Weston cell, the temperature coefficient of the unsaturated cell is very small (about 1 pV/°C) and the cell does not require careful thermostating. The unsaturated cells are placed into plastic cases with copper shields to provide for temperature equilibrium at both electrodes. 

2 Reserve Batteries with Automatic Electrolyte Injection of Electrolyte (Ampoule Batteries) 

In these types of batteries the electrolyte solution is kept in special containers (ampoules) inside the battery. The battery can be activated either pneumatically (Fig. 4.4) by rupturing a special membrane with an exploding cartridge (2). Gas released from a high-pressure gas bottle (1) compresses an elastic ampoule (3) containing the electrolyte breaks through a membrane at the ampoule neck and fills the electrode chamber (5). Reverse valve (4) prevents the electrolyte reflux. 

3 Reserve Batteries with Molten Electrolyte (Thermal Batteries) 

In normal condition the electrolyte (a salt mixture) is solid and has no conductivity so that the batteries can be stored for a long time. Batteries of this type contain two parts (i) the battery proper and (ii) a device for activating the battery by exploding pyrotechnic heaters ignited by fuses and thus instantly raising the temperature above 

---

Reserve batteries have been developed for appHcations that require a long inactive shelf period foUowed by intense discharge during which high energy and power, and sometimes operation at low ambient temperature, are required. These batteries are usually classified by the mechanism of activation which is employed. There are water-activated batteries that utilize fresh or seawater electrolyte-activated batteries, some using the complete electrolyte, some only the solvent gas-activated batteries where the gas is used as either an active cathode material or part of the electrolyte and heat-activated or thermal batteries which use a soHd salt electrolyte activated by melting on appHcation of heat. 

Zinc-silver oxide batteries as primary cells are known both as button cells, e.g., for hearing aids, watches, or cameras, and for military applications, usually as reserve batteries. Since the latter after activation have only a very short life (a few seconds to some minutes), a separation by cellulo-sic paper is generally sufficient. 

The aluminum-air fuel cell is used as a reserve battery in remote locations. In this cell aluminum reacts with the oxygen in air in basic solution, (a) Write the oxidation and reduction half-reactions for this cell, (b) Calculate the standard cell potential. See Box 12.1. 

Liquid ammonia, high energy reserve batteries, 3 467... 

Electronic Time Fuze. Development of an electronic time fuze which would be substantially more accurate than exisitng time fuzes is described in the report of Texas Instruments, Inc (Ref). A programmable digital circuit is driven by. an oscillator based on a Picatinny Arsenal design. As power source, two types of battery, a silver-zinc primary battery and a reserve battery which uses ammonia as the electrolyte, were tried. A detailed manufacturing plan is included as an appendix... 

Zinc-silver oxide reserve batteries have application as power sources for various systems in manned and unmanned space vehicles. 

In previous sections of this chapter, magnesium anodes have been considered as replacements for zinc in Leclanche and air-depolarized cells. In sea water-activated reserve batteries, magnesium anodes are coupled with either silver chloride, lead chloride, manganese dioxide or, occasionally,... 

Lithium-thionyl chloride cells are also constructed as reserve batteries... 

The lilhium-Uiiouyl chluridc, or die lithium-sulfur dioxide, system is often used in a reserve battery configuration in which the electrolyle is slored in a sealed compartment which upon activation may be forced by a piston or inertial forces into the interelectrode space. Most applications for such batteries arc in mines and fuse applications in military ordnance. 

One variant of the liquid cathode reserve battery is the lithium-water cell in which water serves as both the liquid cathode and the electrolyte. A certain amount of corrosion occurs, but sufficient lithium is provided to compensate. These cells are mostly used in the marine environment where water is available or compatible with the cell reaction product. Common applications are lor torpedo propulsiuu and to puwer sonobuoys and submersihles. 

They could serve as reserve batteries to be used with an electrolyte of sea water. Despic (1981) utilized the properties of A1 alloys with tin to shift the potential of A1 in the negative direction and increase the potential of the cell formed with Oz. The CF ion in sea water breaks down protective layers that would reduce the rate of anodic dissolution in an Al-02 battery. In fact, in sea water, such batteries can function at the extraordinarily high rate of 1 A cm4. The watt hours per kilogram at low rates of discharge are 500, which is well above the practical range for other batteries. In view of the commercialization of mechanically rechargeable Zn-air batteries for automotive applications, the commercialization of A1 batteries in the United States is conspicuous for its slowness.38... 

The principle of a reserve battery is to restrict the ionic conductivity between the negative and positive electrodes within the cell by precluding the introduction, or at least the activity, of the electrolyte until activation is required. This approach affords batteries with the longest possible shelf lives, decades or longer under optimal conditions. Reserve batteries can be aqueous or nonaqueous. 

Thermal batteries are a special class of reserve batteries which take advantage of the long-term stability intrinsic to many interfaces when both the active material and the electrolyte are solid state, at least until activation. The stability is attributable to the very low diffusion coefficients of electrolyte ions in the solid state for the chosen electrolyte systems. These batteries are fully assembled with electrolyte present, but the electrolyte remains a solid nonconductor until it is melted by rapid heating from a pyrotechnic heat source. 

Refs. [i] Dell RM, Rand DAJ (2001) Understanding batteries. The royal society of chemistry, Cambridge, pp 87-97 [ii] Linden D (1994) Reserve batteries. In Linden D (ed) Handbook of batteries, 2nd edn. McGraw-Hill, New York, part three, chaps. 16-22 [iii] Crompton TR (2000) Battery reference book, 3rd edn. Newnes, Oxford, p 56/12... 

Theoretical capacity (of batteries) - capacity Thermal battery - reserve battery Thermal cell - thermocell... 

In spite of the numerous difficulties that exist for lithium-metal systems, three examples. Nos. 7-9, were temporarily commercialized. A large primary reserve battery, Li/Mn02 with an organic electrolyte system, was developed by the Hoppecke Co. (data 16 kWh, 100 V, 1.5-6 kW, 55 kg) 34 cells with 200 Ah and 270Wh/kg... 

---