Cycle life of a battery

In terms of life-cycle costs, batteries are usually the most expensive component of a RAPS system and, therefore, it is advantageous to minimize the required capacity. The battery should, however, be sized to supply a significant portion of the anticipated daily load in the absence of diesel- or PV-generated power, e.g., from 20 to 50%. This would allow the diesel to remain idle for much of the day and to operate under relatively constant, high-load conditions for only a few hours each day. Further, the battery should be sized such that the daily depth-of-discharge (DoD) is limited in the interest of enhancing battery cycle-life. (The cycle-life of a battery is affected by several factors which include DoD, temperature, and charging procedure.)... 

NAM structure, thus ensuring longer battery cycle life. We should point out that the cycle life of a battery with electrolyte concentrations in the H-regions can be also limited by side effects and probably corrosion of the positive grid. 

The electrolyte may further include an additive selected from Uthium bis(oxalate)borate, lithium bis(salicylato)borate, and a combination thereof. These compoimds improve the thermal stability of an electrolyte and the cycle life of a battery. 

The cycle life of a rechargeable battery depends on the long-term reversibility of cell chemistries, and the electrochemical stability of the electrolyte plays a crucial role in maintaining this reversibility. In electrochemistry, there have been numerous techniques developed to measure and quantify the electrochemical stability of electrolyte components, and the most frequently used technique is cyclic voltammetry (CV) in its many variations. 

Various additives are used for the Ni-Cd batteries to improve the battery performance. Additives are selected based on their special functions to improve the electrode structure and/or electrode chemical and electrochemical properties. For example, cadmium hydroxide Cd(OH)2 is added to the cathode to prevent phase segregation and to help maintain a single phase of the solid solution during the transfer between Ni(OH)2 and NiOOH in charge and discharge processes. Because Cd(OH)2 is isomorphous with both Ni(OH)2 and NiOOH, this structural functionality can improve the cycle life of the battery. Cd or CdO can increase the overpotential of oxygen evolution... 

A number of problems connected with battery construction and operation, such as rechargeability into the two-phase region which requires improvement of sulfur transport away from the solid electrolyte and carbon surface,and development of sealing techniques and of ceramic mass production, have been to a great extent overcome. The remaining difficulties are primarily connected with the reliability and cycle life of the battery. 

The beneficial effect of compression in extending the cycle-life of VRLA batteries was confirmed in a project carried out by the Advanced Lead-Acid Battery Consortium (ALABC) [17]. The work also showed that the composition of the micro-fine glass separator has an important influence on cycle-life, namely, a higher... 

Ceramic separator. A rigid ceramic separator has been developed by Corning, Inc. [45], with the purpose of improving the cycle-life of VRLA batteries by... 

The essential attributes of the ideal material for use as a separator in VRLA cells are now well understood. A wide range of materials and material combinations has been evaluated for this purpose, and it has emerged that materials with small pore size (high surface area) and very little compressibility show good prospects for extending the cycle-life of VRLA batteries. 

There have been a small number of reports published recently that describe the development of purpose-built batteries for RAPS systems. A VRLA battery for use in PV power systems has been described by Shiomi et al. [27]. The negative plates contain a high level of carbon, but the particle size and concentration of the additive are not described. The recommended level of carbon is simply given as ten times normal levels . The type of VRLA battery used in the experiments is also unclear. Batteries with and without the additional carbon were operated under simulated PV duty for extended periods. Increasing the carbon by ten-fold was found to extend the cycle-life of the batteries from 400 to 1000 cycles. This improvement was attributed to the formation of a conductive network of carbon around the peripheries of lead sulfate crystals. The subsequent increase in conductivity was claimed to improve the rechargeability of the negative plates and, thereby, to suppress the accumulation of lead sulfate. 

Tin improves the mechanical properties of Pb—Ca—Sn alloys. It reduces the passivation phenomena that proceed on the positive battery plates and improves the corrosion resistance of the positive grids. Tin increases also the creep resistance of the Pb—Ca—Sn alloys and thus sustains a good contact between the CL and the PAM. The combination of high corrosion resistance and high creep resistance of the grids prolongs the cycle life of the batteries. 

Lead—calcium—tin alloys with 0.06—0.08 wt% Ca and 0.6—1.5 wt% Sn are used for the manufacture of positive grids for maintenance-free, valve-regulated, automotive and stationary batteries. Cast grids have a coarse-grained structure and ensure stable battery operation. They are highly corrosion resistant and thus can guarantee long cycle life of the battery. 

In most cases, successful hybridization of two or more power sources is expected to prolong the cycle life of a resulting systan since each component performs at the power and/or energy conditions that are close to their respective optimum range. The best utilization of a hybrid system is often assured by the sophisticated hybrid electronic battery management system (BMS) much work has been done on simplifying the BMS for the emerging hybrid power systems [1, 11-15]. Even with the current improvements, the need for a DC/DC converter to link the hybrid components to the power bus still contributes to mass, value, Ufe, and cost analysis of the hybrid system and presents an opportunity for improvement. 

Figure 18.46 Dischargeable capacity during the cycle life of a lithium ion battery (Tadiran). (From Luski et al. in Ref. 10.)... 

Table 7.7 Typical Cycle Life of a Rechargeable Battery versus Rated Capacity of the Battery...

Deep-cycle batteries require good cycle life, high energy density, and low cost. The cycle life of a deep-cycle battery is usually longer than that of an SLI battery. The longer cycle life is achieved in the following manner ... 

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