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FIAMM Energy Technology S.p.A
11. VENTILATION (in accordance with EN
50272-2)
During normal operating conditions, lead acid batteries
emit low quantity of gases which can reach an explosive
mixture when hydrogen concentration is higher than
Lower Explosion Limit (LEL) threshold which is 4%vol.
The purpose of ventilating a battery location or enclosure
by natural or forced (artificial) ventilation is to maintain
the hydrogen concentration below the above stated limit.
Battery locations and enclosures are to be considered as
safe from explosions, when the concentration of
hydrogen is kept below this safe limit.
The minimum air flow rate for ventilation of a battery
location or compartment shall be in accordance with
European Standard EN 50272 calculated by the
following formula:
Q
0,05
x
N
x
where:
Q = ventilation air flow in m
N = number of cells (each 2 Volt)
C
= capacity C
[Ah] at 1.80 Volt/cell at 20°C.
rt
10
The current I
[mA/Ah] producing gas as indicated in
gas
the table of the above mentioned standard con be
assumed as:
I
1
gas
I
8
gas
11.1. Determination of openings
The amount of ventilation air flow shall preferably be
ensured by natural ventilation, otherwise by forced
(artificial) ventilation. Battery rooms or enclosures
require an air inlet and an air outlet with a minimum free
area of opening calculated by the following formula:
A
28
x
Q
with
Q = ventilation flow rate of fresh air [ m
A = free area of opening in air inlet and outlet
2
[cm
]
Note: For the purpose of this calculation the air velocity is
assumed to be 0,1 m/s.
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 separation distance of 2 m when
openings on the same wall.
This document and the confidential information it contains shall be distributed, routed or made available solely with written permission of FIAMM Energy Technology.
FIAMM Energy Technology S.p.A. reserves the right to change or revise without notice any information or detail given in this publication.
Installation & Operating Instruction -Technical Manual
-3
I
x
C
x
10
gas
rt x
3
/h
For batteries on float
For batteries on boost charge
The following picture gives an indication of the correct
opening to assure a complete battery room air exchange
11.2. Forced ventilation
Where an adequate air flow Q cannot be obtained by
natural ventilation and forced ventilation is applied, the
charger shall be interlocked with the ventilation system
or an alarm shall be actuated to secure the required air
flow for the mode of charging selected. The air extracted
from the battery room shall be exhausted to the
atmosphere outside the building.
11.3. Close vicinity to the battery
In the close vicinity of the battery the dilution of
explosive gases is not always secured. Therefore a safety
distance extending through air must be observed within
which sparking or glowing devices (max. surface
temperature 300 °C) are prohibited. The dispersion of
explosive gas depends on the gas release rate and the
ventilation close to the source of release. For calculation
of the safety distance d from the source of release the
following formula applies assuming a hemispherical
dispersal of gas. The safety distance "d" is given from
the following formula:
d
28
8 ,
3
/h]
where N depends on the number of cells per monoblock battery
(N) or vents openings per cell involved (1/N).
or vents openings per cell involved
For further information please refer to EN50272
Standard or contact FET at:
Note: A calculation program is available on
Edition 03/2018 Rev.7
3
3
3
x
N
x
I
x
C
gas
rt
infostandby@fiamm.com
request.
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