G. Papazov

Influence of cycling current and power profiles on the cycle life of lead/acid batteries

Abstract Batteries are assembled with positive plates of the novel strap grid tubular (SGTP) design described in a previous paper [1]. These batteries are subjected to four tests: (i) Peukert dependence determinations; (ii) classical galvanostatic cycling (5 h charge and 1 h discharge); (iii) EV-SFUDS, and (iv) EV-ECE-15 cycling tests. It has been established that the Peukert dependence curve of SGTP batteries is very close in profile to that for SLI batteries. This guarantees SGTPs batteries high power performance. These batteries endure over 950 cycles on galvanostatic cycling. When cycled according to the SFUDS power profile under a current load of 320 A/kg positive active mass during the 15th SFUDS step, SGTP batteries exhibit a cycle life of 350–450 cycles. If the current density during the 15th step is 190 A/kg PAM, the batteries endure over 600 charge/discharge cycles. The life of positive SGT plates is limited by power loss, but not by capacity. Similar results have also been obtained from ECE-15 cycle-life tests. On cycling SGTP batteries with a current load of 210 A/kg PAM during the 23rd ECE-15 step (the step during which maximum power output is demanded from the battery), they endure between 550 and 650 charge/discharge cycles. A summary of the test results obtained for two batches of experimental batteries indicates that there is a direct dependence between the SGTP battery cycle life and the maximum current density on discharge. Increasing the discharge current density decreases the battery life. It has also been established that the capacity on SFUDS (ECE-15) discharge declines gradually on cycling in favour of the residual galvanostatic capacity at 5 h rate of discharge (100% depth-of-discharge) which increases. This implies that two types of structures are formed in the positive plates on cycling: the first type ensuring high power output and the second type yielding low power but long cycle life. The higher the power delivered by the positive plate, the faster the conversion of the structure supporting this high power output into such yielding low power performance. EV-SFUDS: A simplified version of the Federal urban driving schedule for electric vehicle battery testing, US Department of Energy, USA, 1988, and ECE-15: a standard European test cycle, speed versus time.

Mass transport during lead-acid battery plate formation

Abstract Mathematical equations for mass transport during the formation of the lead-acid battery positive and negative plates have been deduced. It has been shown that both the amount of material transferred between the reaction layer and the bulk of the electrolyte, and also the material flow direction depends on the paste composition and the formation current density. The zone within the plate, where the formation processes occur, is determined by the flow direction and by the maintenance of the electroneutrality of the solution. By measuring the potential of both the positive and the negative plates, with respect to a mercury reference electrode, it has been established that their polarization depends on the difficulties of mass transport through the porous structure of the plate.

Influence of the lead dioxide active mass on the corrosion rate of the spines of positive lead—acid battery plates

Abstract Weight measurements were used to determine the corrosion rate of the spines in tubular lead dioxide electrodes with active mass. It was established tha

The effect of current density and thickness of the active mass upon the corrosion rate of the spines of lead-acid battery plates

Abstract The effect of current density and the thickness of the active mass upon the corrosion of the spines of tubular lead-acid batteries has been determined by measuring the corrosion rate by the weight loss method. The presence of antimony in the alloy decreases the overvoltage of the corrosion reaction. Study of electrodes of different active mass layer thickness shows that with increase in thickness the corrosion rate decreases. If the thickness is above 3 mm, the corrosion rate remains constant, and is affected only by the nature of the alloy. The density of the active mass does not affect the corrosion behaviour of the electrodes. The experimental results confirm the validity of the oxygen corrosion model.

Activity and corrosion of tungsten carbide recombination electrodes during lead/acid battery operation

Abstract The oxidation of the tungsten carbide (WC) catalyst in recombination electrodes partially immersed in H 2 SO 4 solution was investigated when the electrodes operated in an atmosphere of oxygen and hydrogen. It has been established that after a long operation period (400 h) 60 to 70% of the catalysts, depending on the initial active surface of WC, may be oxidized to WO x , whereby the rate of recombination decreases about three times. It is assumed that the oxidation of WC is due to the H 2 O 2 formed as an intermediate product of the recombination of hydrogen and oxygen. Silver accelerates the decomposition of H 2 O 2 and hence the use of a WC—Ag mixture as catalyst in the recombination electrodes reduces strongly the carbide corrosion.

Performance of tungsten carbide recombination electrodes under various operating conditions

Abstract The performance of tungsten carbide (WC) recombination electrodes in lead/acid batteries with flooded, gelled or immobilized electrolytes has been investigated under various operating conditions. It has been established that the rate of recombination of hydrogen and oxygen on WC electrodes mounted in batteries with immobilized and gelled electrolytes is considerably higher than that on partially immersed electrodes in flooded batteries. This increase in the recombination rate is due to the increased temperature of the WC electrodes as a result of the exothermal process of water formation. When partially immersed electrodes are used, a heat exchange takes place between the electrodes and the electrolyte and hence the rate of recombination grows. If, however, the recombination electrodes are not in contact with the electrolyte and the recombination rate reaches values higher than 200 cm 3 h −1 cm −2 , the hydrogen/oxygen gas mixture may explode.

Application of WC Electrodes in Stationary Batteries

The main reactions involved in thie clharge process of positive and negative lead-acid battery plates are associated with electrochemical decomposition of water. TIo avoid fallinig downI of the electrolyte level, the battery must be regularly topped up withi water, i.e. it requir-es miaintenance In priniciple, two methlods hiave beeni developed to reduce water loss durinig battery operation. Thle first inivolves inicreasing the overvoltage of hiydrogein and oxygen evolution by the use of special alloys, and limiliting the clharge voltage to below the voltage of water decompositioni. The second approach to imasiilnteniance-lfr-ee operation is to enicoLur-age tle recombiniationi of the hydrogen anti oxygeni released in the ceML. This can be achieved tlhrough: (a) an oxygen cycle, whereby the oxygeni released on the positive plate is reduced on the negative one; (b) recombinatiotn of the released gases to water on the catalytic plug; (c) oxygen reduction and hydrogen oxidation on the partially-inimiersed catalytic electrodes. It was established in the 1970s [1,21 that tunigsten carbide (WC) hiad good catalytic activity towards the 1-12 reaction in1H2SO4 electrolyte. Trhe aims of the present study are to inivestigate the catalytic activity of WC towai-ds hydrogen and oxygen released during lead-acid lbaittery operation, and to develop a lead-acid battery with partially immnersed WC clectrodes.