Calculators Motive

Calculator: Airflow

In EN 50272-3 it has been stated, that the necessary ventilation airflow for a battery location or compartment shall be calculated by the following formula:

Q = v * q * s * n * Igas * Cn / 100 [m3/h]

Resolved into = 24 * 0,00042 * 5 * n * Igas * Cn / 100

Final formula

Q = 0,05 * n * Igas * Cn / 100 [m3/h]

Q = Ventilation air flow [m3/h]
v = Necessary hydrogen dilution factor: 24
q = 0,42 * 10-3 [m3/h] generated hydrogen
s = Safety factor: 5
n = Number of cells
I gas = Current producing gas during the gassing phase of charge [Amp/100Ah] See Table 1.
C n = Nominal capacity [Ah]

Table 1

Charger characteristic

I gas : vented cells

I gas : valve regulated cells

IU:Voltage limit = 2,4 V/c



IUI: No voltage limit

max 6

max 1,5

W: Taper charging

Typical values in the range of 5 to 7


The specified values are for "worst case" conditions

Natural ventilation

In battery rooms, areas and enclosures require an air inlet and outlet, each with a minimum free area of opening calculated by the following formula: Area = 28 * Q [cm2]
For the purpose of this calculation the air velocity is assumed to be >0,1 m/sec

Large and well ventilated rooms shall have a free volume of at least 2,5 * Q [m3]
For the purpose of this calculation the air velocity is assumed to be >0,1 m/sec

The air inlet and outlet shall be located at the best possible location to create best conditions for exchange of air, i.e.

  • openings on opposite walls,
  • minimum distance apart of 2 m when openings on the same wall.The air extracted from the charging area/room shall be exhausted to the atmosphere outside the building

Removable covers or seats shall be removed prior to charging

Suitable ventilation openings shall be provided in the battery container, compartment or cover so dangerous accumulations of gas do not occur.

Where the airflow Q con not be obtained with natural ventilation, forced ventilation shall be used to secure the required exchange of air for the mode of operation.