Electrical Engineering ⇒ Topic : Load Characteristic of a Lead-acid Cell
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Maninder
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Load Characteristic of a Lead-acid Cell The curve between terminal voltage of a lead-acid cell or battery of such cells and the load current is called load characteristic of the cell or battery. Fig. (a) shows the load characteristic of a lead-acid battery (or secondary battery). Note that the value of current is positive for discharge and negative for charge
Figure (a) Let V = Terminal voltage of the battery E = E.M.F. of the battery I = Discharging current r = Internal resistance of the battery Terminal voltage V of the battery is given by V = E - Ir ... for discharge For charging, l is negative so that V = E + Ir ...for charge The load characteristic shown in Fig. (a) is linear but it will be so if E and r remain constant.However, these conditions are not realised in practice because the values of E and r depend upon the state of charge of the battery. For example, the e.m.f. of a fully charged battery is about 2.2 volts/cell and its value decreases as the battery discharges ; being 1.8 volts/cell for a fully discharged battery. | |
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