The Valve-regulated Battery

Two other reactions must be taken into account during the charging of a VRLA cell. These are, the evolution of hydrogen at the negative plate  

the charging of a VRLA cell is potentially more complex than the charging of its flooded counterpart. During the charging of a VRLA cell, thermodynamic/ kinetic conditions allow the progress of six separate reactions at significant rates two charge reactions (the reverse of reactions (1.1) and (1.2)) and four secondary reactions (1.3) to (1.6). 

There are two alternative designs which provide the gas space in VRLA cells. One design has the electrolyte immobilized as a gel, the other has the electrolyte held in an AGM separator. Gas passes through fissures in the gel, or through channels in the AGM (Fig. 1.4). 

As a result of the move from the flooded to the valve-regulated design it is possible that several of the failure mechanisms discussed above may reappear. 

Replacement of lead antimony alloys with lead-calcium alternatives, as a means to discourage hydrogen evolution, reduces the creep strength of grids so that expansion in the plane of the plate may again become a concern. Use of a separator with insufficient rigidity (i.e., too much compressibility ) may allow expansion normal to the plane of the plate. 

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THE VALVE-REGULATED BATTERY — A PARADIGM SHIFT IN LEAD-ACID TECHNOLOGY... 

In summary, it seems that there is a rapidly increasing market for large batteries in a variety of utility applications. So far, this has mainly been a market for flooded batteries, but it is likely that the valve-regulated battery can replace the flooded battery in utility applications in the same way that it has replaced them in UPS and telecommunications applications. 

THE FUNCTION OF THE SEPARATOR IN THE VALVE-REGULATED LEAD-ACID BATTERY... 

Lead-acid batteries will continue to have, by far, the major share of the standby battery market, due to their outstanding specific-energy, life and cost characteristics. It is expected that there will be a significant growth of the standby battery market during the next few years. Most standby batteries already have the valve-regulated... 

Besides improvement of the utilisation of active materials (lead and lead dioxide), another crucial issue that has been in the focus of battery researchers and design engineers for many years now is the immobilisation of battery electrolyte via its absorption in the glass mat separator or by converting it into gel state. Thus, the valve-regulated lead—acid (VRLA) battery was invented which requires minimum or no maintenance and has found wide application. In the VRLAB construction, die active block in the SLI cell is higher and occupies the upper electrolyte reservoir space, thus increasing the capacity of the cell within the same volume. 

The goal for this battery is to be a substitution for the valve-regulated lead-acid battery (VRLA) as a backup power supply of for telecommunication. Usually, the relay machines of the telecommunication structure are located in remote areas. The VRLA with its short life is inconvenient from a maintenance aspect. Avestor s lithium metal polymer battery drastically reduced the load and cost of the maintenance, because the life of their battery is over 10 years and is maintenance free. Further, the feature of the battery is that the condition of the battery itself can be monitored in remote settings. 

The valve regulated lead acid battery is an important development in lead acid battery technology. These batteries operate on the principle of oxygen recombination, using a starved or immobilized electrolyte. The oxygen generated at the... 

This indicates the strong influence of overcharging on heat generation in sealed or valve-regulated batteries caused by the internal oxygen cycle. 

A frequent argument is that vented batteries require special battery rooms, but valve-regulated batteries do not. Valve-regulated batteries can be accommodated as one likes but in this sense it is not correct. DIN VDE 0510 does not require separate battery rooms. This is a requirement of the owner/user who wants to have specific protection of the supply system, e.g. in case of fire or unauthorized access. This is to ensure system functionality even in cases of crisis (see DIN VDE 0108 Safety Power Supply Systems for Public Premises , Regulations for Electrotechnical Installations in Buildings.)... 

For valve-regulated batteries new methods of measurements and monitoring are necessary. Quite a number of automatic monitoring systems have been developed in the past their reliability must be proved in the future. 

Figure 7.27 shows a way to minimize the necessary floor space that is necessary with valve-regulated batteries. In the shown rack 64 bloc batteries are arranged in eight rows one above the other, installed in horizontal position. That makes service very simple because the terminals and connectors are in front of the rack and voltage readings can easily be taken. 

Valve-regulated batteries have been use at Deutsche Telekom since the end of the 1980s. First these batteries were put into low scope purposes for testing. Their use was forced strongly with the extension of telecommunications in the new countries (area of the former GDR), so that today approximately 1700 locations (mainly cell capacities of 200 Ah up to 1500 Ah) with valve-regulated batteries are realized. Since these product series permit the use of batteries in applications in which the use of vented batteries is completely impossible, valve-regulated batteries of small capacity (bloc batteries up to 65 Ah) are used today in most facilities. Main focuses of use are converters for the transition from copper wires to glass fiber. 

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