|
6.10.1 The test shall be carried out with six cells or three monoblocs connected in series having undergone no conditioning treatment.
6.10.2 The units shall be maintained at a temperature between 20 °C and 25 °C and fitted with a gas collection device so that the emitted gas can be collected over several days.
6.10.3 The gas collection shall be carried out, for example, with a gas collection device similar to that shown in Figure 1 with an attention to a leak-free gas transport from the units to the collection device, an adequate sample volume for long unattended operation and a maximum hydrostatic head of 20 mm as given by the difference in collection vessel immersion depth and water level.
6.10.4 Gas emission intensity with constant voltage
The units shall have a demonstrated capacity Ca equal to, or higher than, rated capacity C20, be fully charged and float-charged for (72 ± 1) h with the manufacturer's specified float voltage Uflo.
6.10.5 After (72 ± 1) h of float charge, commence the gas collection and continue collecting gas for further (192 ± 1) h. Record the cumulative total actual gas volume collected Va over the period of (192 ± 1) h, noting the ambient temperature Ta and the ambient pressure Pa at which the determination of the gas volumes were made.
6.10.6 Calculate the normalized volume of gas Vn emitted by each unit at 20 °C and 101,3 kPa reference pressure where
V n=（ V a ×T r/ T a）×（P a/ P r） (3)
where
Vn is the normalized gas emitted (ml);
Va is the cumulative total gas collected (ml);
Tr is the reference temperature (K): 20 °C = 293 K;
Ta is the ambient temperature (K): Ta = 273 + T in °C;
Pa is the ambient atmospheric pressure (kPa);
Pr is the normalized pressure (kPa): Pr = 101,3 kPa.
6.10.7 Calculate the specific gas emission Ge per cell at normal float voltage conditions with the formula below:
Ge = Vn / (n×t×Crt) (4)
where
n is the number of cells from which the gas was collected in the collection vessel;
t is the number of hours during which the gas was collected;
Crt is the rated 20 h capacity to 1,75 Vpc of the units from which the gas was collected.
6.10.8 Gas emission intensity with constant current
If constant current charging is recommended, gas emission intensity has to be carried out with constant current. In this case the requirements of 6.10.4 to 6.10.7 have to be replaced by the requirements of 6.10.9 to 6.10.11.
6.10.9 The units shall have a demonstrated capacity Ca equal to, or higher than, rated capacity C20, be fully charged and then charged with constant current of 2 × I20 for (48 ± 1) h.
6.10.10 After 24 h constant current charge collect the gas emitted during charging over a period of 5 h with I = over the period of 5 h 0,1 × I20. Record the cumulative total actual gas volume collected (Va in ml) noting the ambient temperature Ta and the ambient pressure Pa at which the determination of the gas volumes were made.
6.10.11 The gas recombination efficiency can be calculated by equations (5) and (6). The quantity of released gas converted to 101,3 kPa at 25° per charged ampere-hour is defined by equation (5).
õ = Pa/ Pr × 298 / (Ta + 273) × Va / Q × 1 / n (5)
where
Pa is the atmospheric pressure at the time of measurement (kPa);
Pr is equal to 101,3 (kPa);
Ta is the ambient temperature for burette or graduated cylinder (°C);
Va is the quantity of the released gas collected (ml);
Q is the quantity of ampere-hours loaded during gas collection;
n is the number of cells.
The gas recombination efficiency is
ç = (1 – õ / 684) × 100 [%] (6)
where
684 is the theoretical quantity of the released gas with 101,3 kPa at 25 °C per Ah (ml/Ah).
|