Battery charger with indicator for indicating full charge of secondary cells or battery thereof

A battery charger with an indicator to indicate full charge of secondary sealed cells and like cells which become heated when subjected to overcharge current, or batteries of such cells, the indicator comprising a heat sensitive mechanism which is mounted to the charger housing and is adapted to change a perceivable characteristic in respone to the rise in temperature of the cell or battery as the charging operation continues beyond full charge. Part of the heat sensitive mechanism is thermally coupled to the battery or cell and another part is maintained at ambient temperature so that the perceivable characteristic of the portion maintained at ambient temperature and that of the portion at the raised temperature of the overcharged battery or cell can be readily observed to signify that full charge has been attained. As preferably embodied, the heat sensitive mechanism is a liquid crystal material.