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Module 1: Electroquímica

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Recarga de la batería de plomo ácido

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Chemistry - Recharging of the lead-acid battery

Recharging of the lead-acid battery

During recharging, electrons are dragged off the positive electrode, so
oxidation occurs there to replace the electrons, and forced onto the
negative electrode, so reduction occurs there to use up the electrons. If
recharging a lead-acid accumulator, using a battery charger, you should
connect the (-) terminal of the battery charger to the (-) terminal of the
lead-acid accumulator.

The negative electrode, which acts as the anode during discharging,
becomes the cathode during recharging. The positive electrode, which acts
as the cathode during discharging, becomes the anode during recharging.
This is represented in the diagram below:

The diagram above shows that the electrode that acts as the anode during
discharging, acts as the cathode during recharging, and vice versa. This
emphasises the fact that the purpose of recharging is to put the cell back
the way it was. The reaction occurring at each electrode during recharging
is the reverse of the reaction occurring at that electrode during
discharging.

During recharging, a potential difference greater than 2.05 V is applied
across the electrodes in each cell, forcing the reverse of the discharging
reaction to occur.

A potential difference greater than 2.05 volts is required to force the
electrons to flow in the reverse direction i.e. from the (+) electrode to
the (-) electrode. In essence, recharging (a characteristic of secondary
cells) involves reversing the electrode reactions that occur during normal
use of the cell.

The sign on each electrode does not change from discharge to recharge, but
the process that occurs does. This is why we always define the anode as the
electrode where oxidation occurs and the cathode as the electrode where
reduction occurs.

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