User manual
24
© 2006, Elektro-Automatik GmbH & Co. KG
Irrtümer und Änderungen vorbehalten
EN
© 2009, Elektro-Automatik GmbH & Co. KG
II. Nickel Cadmium / Nickel metal hydride batteries
The charging procedure for Nickel batteries follows an
I-U characteristics with automatic stop when the battery
is fully charged. Also see gure below.
The rst charging phase is a precharge phase with
reduced output current I
PC
. The precharge is very ef-
fective for heavily discharged batteries, providing the
possibility to prepare them gently for the charging.
After the charging voltage has risen to U
PC,END
or time
t
PC,END
is exceeded
,
the device changes to boost
charge with current I
CHARGE
. During the boost charge
the battery voltage will continuously rise. The highest
measured value serves as as reference for the determi-
nation of voltage difference ∆Ua. This difference results
when the battery voltage sinks again at the point where
the battery is fully charged. If the dened value ∆Ua is
exceeded, the battery is considered as fully charged
and the charging stops automatically.
Functional description
When charging Nickel batteries, the battery tempe-
rature is very important and has to be supervised.
Changes of the battery surface temperature may not
exceed a certain level. Thus is imperative to use and
install a temperature sensor. At the start of the charging,
the start temperature is measured. If the temperature
difference exceeds the value ∆T a,max or if it rises
within a minute so that value ∆T/∆t a is exceeded, the
charging is aborted. The battery capacity is additionally
supervised. A premature abort will happen if 1.3 Q is
reached for any reason, i.e. 130% of the battery capa-
city. Given, that the battery capacity was correctly set
in the battery prole, this will prevent the battery from
overheating.
Attention! In case the charging is started without
temperature sensor, there can‘t be a temperature-
depending fast charge with high C value.
Figure 2. Charging characteristics for Nickel batteries