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Battery ventilation

Calculates the flow needed to vent a battery room or battery locker to keep the hydrogen concentration below the Lower Explosive Limit (LEL).

Battery ventilation

Input Result
Thinning factor v=
Generated hydrogen q= *10-3 m3/Ah
Safety factor s=
Number of cells n= pc
Capacity C Ah
Gas generating current Igas= mA/Ah
Flow Q=
Min area A= cm2
Safety distance d=

Gas generating current

Indata Resultat
Float-/boost charge current Ifloat/boost= mA/Ah
Gas discharging factor fg=
Safety factor fs=
Current that generates gas Igas= mA/Ah


Thinning Factor

A factor that indicates how large the necessary dilution of the hydrogen is and is determinable as below:

(100% -4%) / 4 = 24%

Generated Hydrogen

The amount of hydrogen generated per Ah.

Safety Factor

A general safety factor.

Number of cells

The total number of cells in the battery or batteries.


Refers to the rated capacity of the battery. For lead-acid batteries comes 10h capacity while nickel-cadmium (NiCd) batteries are the 5h capacity as said used in the calculations and in both cases, it is at 20 ˚ C

Gas generating power

The current that the charge gives rise to vätgs formed.


The computed flow needed for the hydrogen concentration should be less than 4%.

Min area

The minimum clear area for input repsektive emissions required for natural ventilation.

Float-/boost charge current

If data for Ifloat och Iboost are missing can table below with the data used to determine Igas.

Free ventilated lead acid batteries (Sb < 3%) Valve regulated lead batteries NiCd batteries vented cells
Gas discharging factor fg 1 0,2 1
Safety factor fs 5 5 5
Float voltage ufloat 2,23 2,27 1,4 V/cell
Float current Ifloat 1 1 1 mA/Ah
Current Igas 5 1 5 mA/Ah
Boost charging voltage uboost 2,4 2,4 1,55 V/cell
Boost charging current Iboost 4 8 10 mA/Ah
Current Igas 20 8 50 mA/Ah

Float-/boost charge current increases with increasing temperature. The values ​​in the table above apply up to about 40 ° C

Used recombinant cell valves are the gas-generating current I gas is reduced to 50% of the ventilated cells.

Gas discharging factor

One factor that shows some of the power of a fully charged battery that generates hydrogen gas.

Safety factor

Safety factor takes into account the Old or faulty cells in the battery.

Safety distance

Displays the distance from the batteries where the dilution of the hydrogen gas to a safe level can be considered significant. The distance may vary depending on the battery manufacturer's safety calculations or measurements.


Flow: Flow
Current: Current
Min area: Min area
Safety distance: Safety distance