About batteries: Lead-antimony batteries

The basic principle of the convential battery is a grid plate casted from an alloy of lead and antimony, sometimes up to 12% or more. It is basically basically the same battery with pasted plates invented by Volckmar and Sellon 120 years ago. The antimony strengthens the soft lead, improves adhesion of active mass and protects against corrosion. Often additional components such as selenium and arsenic are added in order to further improve the properties.

At the end of charge the antimony can produce a very poisonous gas called stibine or antimony hydride (SbH3). It has the distinctive smell of rotten eggs. Stibine is thermally not very stable: it dissolves slowly at room temperature. The decomposition products are hydrogen and metallic antimony. The latter will be deposited on the negative plate. As a result, the gas voltage at the negative plate will be reduced with sometimes 200mV so the battery will produce more gases and thus consume more water. At the same time the rate of self-discharge will increase.

As more antimony is deposited on the negative plate more stibine will be produced during charging. More stibine means more deposit on the negative plate, and this is why a high antimony battery will suffer from higher water consumption and self-discharge as it gets older.