Cell voltage lead acid

Fig. 5.9 Lead-acid cell voltage charge for a constant charge as a function of time...

Experimentally measured and calculated values for lead—acid cell voltage as a function of H2SO4 relative density, as reported by different authors. 

Dependence of Lead-Acid Cell Voltage on Temperature and H2SO4 Concentration... 

Table 1 gives the calculated open circuit voltages of the lead—acid cell at 25°C at the sulfuric acid molalities shown. The corrected activities of sulfuric acid from vapor pressure data (20) are also given. 

The first difference between these two batteries is the voltage they produce a watch battery produces about 3 V and a lead-acid cell about 2 V. The obvious cause of the difference in emf are the different half-cells. The electrode potential E is the energy, expressed as a voltage, when a redox couple is at equilibrium. 

Fig. 5.2 Approximate open circuit voltage and electrolyte density as a function of percentage service capacity for the lead-acid cell...

Suppose a battery-powered device requires a minimum voltage of 9.0 V to run. How many lead-acid cells would be needed to run the device (Remember that a standard automobile battery contains six lead-acid cells connected in one package.) The overall reaction of a lead-acid cell is... 

Calculate the free energy change (heat change) of the cell reaction (AH) in calories for two battery systems (a) A lead-acid cell with an open-circuit voltage of 2.01 V at 15 °C and a temperature coefficient of resistance (dE/dT) of 0.0037 V/K. (b) A Zn-Hg cell (Clark cell) with an open-circuit potential of 1.4324 V at 15 °C and a temperature coefficient of 0.00019 V/K. (Bhardwaj)... 

Calculate the voltage A%° of a lead-acid cell if all reactants and products are in their standard states. What will be the voltage if six such cells are connected in series ... 

V design and comprises six lead-acid cells in a monobloc container. This battery is compatible with the vehicle electrical system that operates in the voltage range from about 12 to 14 V. Until around 1970, 6-V systems were also in use. In European trucks and buses on the other hand, it is common practice for two, 12-V batteries to be connected in series to achieve a nominal voltage of 24 V. 

The voltage efficiency of the lead-acid cell is about 80 %. This near reversibility is a consequence of the rapidity of the chemical reactions in the cell. As we have seen, the ability to supply large currents at potentials near the open-circuit potential means that the chemical reactions at the electrodes are fast as the charge is drained away by the current, the potential should drop, but the chemical reaction occurs rapidly enough to rebuild the potential. 

Changes in cell voltage during the initial stage of formation of a lead—acid cell with formation... 

R n in battery voltage sources varies from about 35 in a 9-V zinc-carbon battery to less than 6 in a lead-acid cell. Electronically controlled sources produce very low an important point to which we will return. 

The internal resistance of a Na/S cell is higher than that of a comparable lead/acid cell. This higher resistance leads to reduced voltage at high current drains and limits the voltage efficiency of the Na/S battery to, typically, 65-85% depending upon the power output. This is not entirely wasteful as some heat output is required, in any event, to maintain the battery at operating temperature-... 

As discussed earlier, sulfuric acid in electrolyte solution is an active material that participates in the cell reaction. Therefore, the sulfuric acid concentration changes during both battery discharge and charge processes. In addition, as predicted by Equation 5.12, the open circuit voltage of a lead-acid cell is a function of electrolyte concentration according to the Nemst equation. Furthermore, the specific resistance of the electrolyte and its freezing point can also depend on the acid concentration. 

FIGURE 23.2 Typical voltage and specific gravity characteristics of lead-acid cell at constant-rate discharge and charge. 

The open-circuit voltage for a battery system is a function of temperature and electrolyte concentration as expressed in the Nemst equation for the lead-acid cell (see also Chap. 2). 

FIGURE 23.4 Open-circuit voltage of lead-acid cell as a function of electrolyte specific gravity. 

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