Alpha Technologies Industrial Ni-Cd Batteries Standard Range - Manual (Page 7)

EN-ALPHA-TMSR-001 (10/09) 7
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A specially developed terminal design with redundant leak protection prevents any leakage of electrolyte. Depend-
ing on the cell range and type terminals are designed as female or male thread and polarity is colored marked.
1.2 Venting System
Alpha batteries can be equipped with a normal fl ip-top vent or with a special gas drying as well as a fl ame
arresting vent.
The originated charging gases (hydrogen and oxygen), which occur during the charging process
of Ni-Cd batteries carry also small electrolyte drops of the electrolyte solution. This accellerates the decline of the
electrolyte level in comparison to the normal water decomposition during overcharging, resulting in more frequent
maintenance. Furthermore, a strong incrustation of the fi lling vents can be due to the creation of carbonate.
The use of the gas drying or fl ame arresting vents reduces the build-up of carbonate material. The vents
contain small plastic particles with a large surface area which capture the electrolyte drops. The capturing of the
electrolyte keeps it in the cell and prevents the build-up of carbonate.
The additional feature of the fl ame arresting vent is the microporous disc on the top. This feature results in a
diffused leakage of the charging gases. Moreover, high local concentrations can be prevented which fi nally leads
to a lower risk of fl ammability. According to IEC 60623 the total amount of entrained potassium hydroxide shall be
not more than 0.05 mg/ Ah during 2 hours overcharge. Alpha batteries with the special venting system improve
the required value many times over to 0.011 mg/ Ah during 2 hours overcharge.
1.0 Alpha Ni-Cd pocket plate cell, continued
Fig.1-2 Battery vents Fig.1-3 Battery terminal cross-section