Standby applications

Some water loss occurs, especially if there is prolonged overcharging of cells. Cells may be designed so as to contain a large reserve of electrolyte, so that topping up is only necessary after long intervals, e.g. 5-8 years in some stationary standby applications. 

Stationary battery (cell) — Rechargeable -> batteries designed to be located at a fixed place. Stationary batteries are used mainly for uninterruptible power supplies (UPS) and standby applications. These cells are usually designed for high reliability and very long -> cycle life under shallow depth of discharge (DOD) conditions. The common chemical systems utilized for the production of stationary batteries are the -> lead-acid and -> nickel-cadmium batteries. Less common, and more futuristic is the - sodium-sulfur battery designed for KW and... 

Figure 27 Comparison of the different battery technologies in terms of volumetric and gravimetric energy density. The share of worldwide sales forNi-Cd, Ni-MeH and Li-ion portable batteries is 23, 14, and 63%, respectively. The use of Pb-acid batteries is restricted mainly in automobiles or standby applications, whereas Ni-Cd batteries remain the most suitable technologies for high-power applications (for example, power tools). (Ref 47. Reproduced by permission of Nature Publishing Group (www.nature.com))...

The majority of VRLA batteries produced today are used in standby applications to provide a reliable source of power in the event of failure of the mains supply. Discharges are infrequent and the batteries are maintained by float charging at a preset voltage. For example, European practice is to use parallel strings (usually 48 V) across a 54.5 V supply (2.27 V per cell). Adequately designed new cells, after conditioning and free of impurities, have a float current of < 1 mA per Ah at 20°C. 

Gravity casting of grids is usually employed for the manufacture of flat positive plates. Flat positive lead-calcium-tin grids are more sensitive and more prone to corrosion than tubular grids. Nevertheless, it must be pointed out that even for batteries with flat positive plates, corrosion has been only one of the limiting factors during standby applications. 

Gel batteries are sometimes produced with phosphoric acid added to the electrolyte and sometimes without. Phosphoric acid is not generally used for standby applications it is mainly used for applications, which includes some cycling. Investigations of the effect of phosphoric acid, especially with regard to an improvement in cycle-life, can be found in the literature [64-70]. According to the results of these investigations, there is an adsorption of phosphoric acid on to the lead dioxide surface, which modifies crystal growth. It has also been pointed out that... 

Sealed lead-acid batteries are in both cylindrical and prismatic shapes. The cyclindrical ones (usually designed as SLA batteries) have excellent high-rate characteristics. Other than in portable devices, sealed batteries can be used in standby applications, e.g. telephone exchange stations, were they are kept in float charge. In this case too, oxygen recombination is possible. 

The reactants compounds lead (Pb), lead sulfate (PbSO J, and lead dioxide (PbOj) are well-defined chemical compounds, and there are no intermediate states of oxidation. As a consequence, any voltage above the open circuit voltage results in complete charge, and equalizing charges are not required when the battery is used under continual charging in standby applications. 

The turnstile antenna is made up of several layers, usually six layers for channels 2 through 6 and twelve layers for channels 7 through 13. The turnstile is not suitable for side-mounting, except for standby applications in which coverage degradation can be tolerated. 

The three major types of nonautomobile applications in which lead-acid batteries play important and necessary roles are (1) stationary applications for large-scale electricity storage (2) standby applications for UPS, telecommunications, and emergency lighting and (3) backup power applications. 

Yuasa claim that, due to the use of heavy-duty grids. 1000 cycles are obtained for their batteries and a normal life of 4-5 years is expected in float charge on standby applications (based on normal charge voltage of 2.28-2.30 V/cell at 20°C). 

Cells with tubular positive plates are normally used to power electric trucks, on which daily recharging is needed. They are also suitable for certain standby applications. They deliver high power at low and medium rates of discharge and work well in adverse conditions. 

It is generally accepted that lead-acid batteries are ideal for standby power systems, because they are reliable and relatively low-cost. When it comes to selection, the choice is between the kinds of battery referred to earlier. Batteries are tailor-made for specific standby applications, and Table 32.2 gives a rough guide to the suitability of different batteries for different jobs. 

There is an all-too-common idea that a battery is a battery and this sometimes leads to car batteries being used to supply standby power. Although this usually results in low initial cost, it has serious drawbacks. Car batteries are designed to supply high currents for short periods and are not intended to carry industrial type loads for any significant periods. Their life expectancy in standby applications is very low compared to that of Plantd and other industrial batteries. More important. 

This range of batteries is particularly suitable for any standby application calling for a good high-rate discharge characteristic. Such applications include electronic computer and telecommunications equipment, which requires a no-break clean power supply free from voltage surges, frequency variations and other transients. 

The long term calendar life of lithium ion cells for satellite and standby applications was studied by Broussely et al. [150]. In experiments, the capacity evolution was tracked as a function of storage temperature. Cells containing either LiCo02 or... 

---