Page 505 - Battery Reference Book

49/6 Methods of charging large nickel-cadmium batteries
battery system must be at least 2m. Doors have to 49.4 Ventilation
open outwards. Electric tools normally causing sparks
must be positioned at least 1 m from the battery. Battery rooms and enclosures must be vented in a
Heating radiators with a surface temperature of more manner such that the hydrogen emitted on charging is
than 200°C are not allowed. Doors, windows, floor diluted by natural or artificial ventilation. The dilution
covers and paints on walls and roofs have to be must be such that the mixture becomes non-explosive.
electrolyte resistant. Windows accessible from outside The amount of hydrogen dissipated during charging a
have to be locked and barred or a wire glass may be battery at ambient temperature of 0°C and a pressure of
used. 1.013 bar is 0.42 I/A h per cell. A mixture of hydrogen
The installation of batteries in cubicles and en- gas and air is explosive if the amount of hydrogen gas
closures with convection venting is allowed up to a exceeds 3.8%. The venting of the battery room should
charging power of only 2 kW. The power is calculated be in accordance with VDE 0510. The air necessary for
from the nominal charging current of the battery. venting battery cubicles or enclosures can be either by
Battery cubicles or enclosures have to be provided with inlet or extraction provided the volume of the battery
venting facilities. room contains at least 2.5 times the necessary air
If there is other electrical equipment in the room, it to be changed per hour to ensure that an explosive
must be separated from the battery by a wall or barrier. mixture does not occur. Battery roorns that comply
Electric tools normally causing sparks are not allowed with regulation VDE 0510 can be regarded as being
near the venting ducts of the battery. explosion proof.