Thales 421, Эксплуатация и обслуживание, Страница: 161 / 256

LLZ 421
Operation and Maintenance Maintenance
ILS 420
6−19
Ed. 01.10 SOAC
6.4.1.3.2 Dry Pre−charged Batteries
Dry pre−charged batteries are activated by the manufacturer. They can be started up simply by filling
the battery with accumulator acid of the specified acid density. The battery can then be operated in
the navigation installation without any further delay. This however applies only to brand new batteries,
since these batteries are extremely sensitive to climatic conditions.If dry pre−charged batteries are
stored for some time without being filled with acid, the plates will gradually become deactivated. This
process is accelerated in a moist or warm environment.They will be completely deactivated after
about 6 months, and the battery must be treated and started up in almost the same way as a non−acti-
vated battery. The initial charging procedure will take more or less time depending on the storage pe-
riod and the state of the plates.
6.4.1.3.3 Non Pre−charged Batteries
These batteries have the longest initial charging period. They can be recognized by the fact that the
acid density drops substantially 1 to 2 hours after filling (density <1.15 kg/l), and/or the acid tempera-
ture rises by a few degrees.
6.4.1.3.4 Initial Charging
WARNING
There is a particular risk during the charging procedure, since oxyhydrogen gas develops
in the gassing level of the battery acid is reached. It is therefore forbidden to use naked
flames or incandescent bodies in the vicinity of accumulators. Sufficient ventilation should
be provided for the battery compartment. The acid vapors are aggressive, therefore care
should be taken of clothing.
The battery manufacturers specify various methods with settings and nominal data. The appropriate
instructions are contained in the handling specifications accompanying with each battery. A constant
current charge (I−characteristic) is used for the battery charged power supply in the navigation instal-
lation. Two test shunts, which generate a voltage drop of 2 mV/A, are installed in the BCPS. Current
measurements can thus be performed via the software.
The acid density and temperature must be measured and noted once an hour during the charging
procedure at every 6th or 3rd cell (test cells). The same applies to the battery voltage, which should
be measured at the battery poles. For voltage measurements see Chapter 6.4.1.1).The duration of
the charging procedure depends on the state of the plates, and should be at least 6 hours. The crucial
factor for determining the end of the charging procedure is that the battery voltage and the acid den-
sity no longer rise over a test interval of 2 hours, and that the nominal values have been reached. If
the acid density and the battery voltage do not reach their nominalvalues despite absolute confor-
mance with the charging specifications, the charging procedure must be continued with the same
charging data for a further 10 hours. If the acid density still does not reach its nominal value, the acid
density must be adjusted. If the density is too low, higher−density acid (mixed acid) must be added.
If the acid density is too high, specially purified water must be used for topping up. The temperature
and acid level must be taken into consideration when measuring the density, in other words the nomi-
nal acid density is valid when the acid level indicator is at max.
If water is lost during the charging procedure on account of gassing, the acid must be topped up with
specially purified water. If it is necessary to correct the acid density or acid level, the battery must be
topped up beforehand with specially purified water. If it is necessary to correct the acid density or acid
level, the battery must be charged again with the same charging values for approx. 1 hour in order
to make sure the acid is properly mixed. This is ensured by means of the gassing which results.The
acid temperature must be monitored during the charging procedure. This is particularly important in
case of high ambient temperatures. The acid temperature may not exceed 55 °C.