Lead Acid (Pb/acid) - 2.0 Volts per cell
| Lead Acid Batteries |
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In the 1970s, sealed cells were commercialized that did not require refilling of the electrolyte compartment. The sealed cells can be safely constructed due to the addition of a catalytic recombiner that produces water from hydrogen and oxygen gases sometimes produced in the charging process. The cells have a nominal discharge potential of 2 V, are inexpensive, and are capable of high power densities (necessary for starting a car, these can be as high as 600 W / kg). However, the cells undergo realtively rapid self-discharge (your neighbor has to start your car, and recharge yuor battery, when you go on vacation), are environmentally unfriendly, have low energy densities - typically less than 100 W hr / kg due to the high density of Pb. Finally, Pb/acid cells can only be cycled a few hundred times, and far fewer cycles are possible if the battery is fully discharged. As many who need to start their cars in the winter know, cell performance is markedly poorer at low temperature. Note that both electrodes dissolve into the electrolyte during the discharge reaction. When charged the reverse reactions occur, although overcharge will lead to the electrolysis of water and consequent production of (hazardous) H2 (g) at the cathode. |
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