What is OPzV Battery?
Under the DIN standards of Europe, OPzV stands for Ortsfest (stationary) PanZerplatte (tubular plate) Verschlossen (closed). Clearly, this is a tubular plate 2V battery cell construction similar to the OPzS battery but having a valve-regulated vent plug rather than an open vent plug. However, no lead-acid battery is truly closed and for this reason, the V in the acronym is often regarded as standing for “Vented” rather than Verschlossen. By vented this means it has a pressure relief valve that will open at internal pressures of around 70 to 140 millibar.
OPzV Battery life
This better utilization results in a higher energy density, whilst the gauntlet holds active material firmly against the conductor to minimize the battery resistance and prevent loss of PAM from shedding during deep cyclic operations.
The immobilization of the electrolyte in the OPzV battery has the dual benefits of allowing operation of the cells in different orientations without spillage and also it enables the gases produced by electrolysis of water on the charge to recombine and prevent the water from being lost.
The recombination aspect is critical to many, particularly remote stationary installations. It means that battery maintenance can be carried out at much-increased intervals since no water topping up is required. It also removes the need for expensive ventilation equipment which is designed to remove potentially explosive gases produced when the battery is being charged.
The problem of gas evolution with flooded cells derives from the electrochemistry of the lead-acid battery. The production of hydrogen and oxygen can occur at very low cell voltages.
The disadvantage of the OPzV battery
However, there are downsides to these two advantages: the high deep cycle life does come at the expense of high rate discharge, or cold-cranking ability, both of which are significantly lower when compared with its AGM flat plate counterpart. The gas recombination is considerably slower than the rate of gas generation. For this reason, the charging process takes longer than a flooded cell, typically up to 15 hours.
Bearing in mind the above discussion, it is fairly clear that this design of the OPzV battery is most suited for those applications where there is difficulty in maintaining the battery and it is required to have frequent, perhaps regular deep discharges combined with a long calendar and cycle life. Because of its relatively low CCA performance, the discharge profile would typically be current draws of 0.2C amps or less over a period of several hours. Although it is fair to say that OPzV battery and cells can provide intermittent, reasonably high discharge currents of up to 2C amps during a normal duty cycle.
The recharge time, which is typically 12 to 15 hours to recharge a battery, limits the amount of gas that can be produced on charge. This is achieved by charging with a voltage limit, typically 2.23 to 2.45 volts per cell. This reduces the current going into the battery and consequently extends the charging time. This is also an important factor when considering different battery markets and their operational profiles. With these considerations in mind, the most suitable application for the OPzV battery is predominantly heavy-duty and industrial.
OPzV Battery applications
Looking at the broad categories in both market sectors, we have:
– Solar power: diesel hybrid, off-grid generation, and storage, domestic storage
– Standby Power
• Rail (Rolling Stock applications)
– Emergency lighting
– Diesel locomotive starter
– Warehousing: Forklift trucks, electric hand trucks, AGV
– EV: Golf cart, Rickshaws
Of the above-listed applications, it is those which require frequent deep battery discharges, with time to fully recharge, for which the OPzV battery is best suited. In a stationary battery application, it would be solar power, BESS, and standby power which ticks all the boxes.
For railway applications, the train lighting and air conditioning battery and railway signaling battery are the best applications for OPzV batteries. The railways need a deep cycle battery that is capable of deep discharge cycles in times of power outages. This is best provided by a tubular battery plate and not a flat plate battery. Considering the huge network of operations of the railways, a maintenance-free battery like the OPzV battery would be a boon to the railways.
The OPzV battery range is not suited for Traction applications such as golf cart batteries & forklift batteries. There are practical considerations such as the use of breakable ABS containers instead of the polypropylene cases used in forklift battery for example. Non-flexible ABS cell jars would easily break if they were to be tightly packed into the steel battery trays of forklift trucks. The Gel OPzV battery design calls for more volumes of active materials which will increase the standard dimensions of a forklift battery.
The leisure market generally opts for lighter weight and higher energy density monoblocs, particularly for caravan and camping applications. The same is generally true of the marine battery applications, which apart from electric boats, use marine batteries for broadly similar uses of refrigeration, navigation, and lighting, and also as with camping, there is limited space for battery storage.
The major use for OPzV batteries is the stationary battery market. The common thread throughout all of the subdivisions in this sector is that the location of the batteries is fixed. The breakdown of the industrial battery market with the main stationary applications of telecoms, UPS, standby power, and battery energy storage systems (BESS), having about a 90% of the share of a 15 billion USD global market. Unlike the traction, leisure, and rail applications (excepting signaling) the stationary battery stays fixed in a single location and is generally hard wired into a power supply system. However, the similarity ends there.
Some applications such as UPS in telecoms and load leveling/frequency control in BESS will require brief or short discharges of high power at random intervals, spending a high proportion of their life on a charge, whilst others such as solar and standby power will be deeply discharged at regular intervals.
For this reason, the OPzV battery is most suited for those sectors of the stationary market that are deeply discharged, regularly or randomly, but certainly frequently. In this category, we can include all solar power installations with larger-scale diesel/solar hybrid installations being the ideal candidates for the longer-lasting more robust construction of the OPzV battery.
The maintenance-free aspect of the OPzV battery is important here, particularly in remote areas where topping up of batteries would be extremely expensive and add to the cost, thereby reducing the ROI to the provider. Similarly, domestic installations benefit from the lack of expertise required in maintaining battery electrolyte levels. Overtopping, topping up at the wrong State of Charge (SoC) of the battery and even neglect are common features in domestic battery usage.
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