Battery charger for the PUMA T2 hand-held radio
Technical Manual
Functional Description
P/N: 779-0357/02
Revision 04
OTE Proprietary Information
Page 31
Li-Ion batteries
In order to optimize the Li-Ion battery life cycle, two distinct charging phases are
realized: the first at constant current (750 mA for BCU6-750; 1,5 A for BCU2-1500
and BCU2-1500/B) till a preset voltage value (8.35
±
0.05V) is reached, then there
follows a constant voltage phase in which the current decreases till 170 mA which
corresponds to the 100% of the cell capacity.
Infact a value of 170 mA is also the cut-off current of the battery charger.
Once this second phase is over the green LED is lit.
NiCd and NiMH batteries
When using NiCd or NiMH batteries, at first there is a voltage controlled constant
current (750 mA for BCU6-750; 1 A for BCU2-1500 and BCU2-1500/B) charging till
the charging cut-off is reached according to one of the criteria implemented by the
battery charger.
As soon as a voltage decrease (technically defined -
∆
V) is detected at the battery’s
terminals, the cells are charged and the fast charging current must come to an end
not to degrade the cells. In this condition the 95% of the maximum capacity has
been reached: this phenomenon is due to the fact that the capacity of absorbing
energy decreases while reaching the end of the charge.
Then the next charging phase, with impulsive current and reduced mean value
(slow charge), counterbalances such phenomenon and lets the battery be charged
with more effectiveness.
When the fast charging is over the red LED turns off and the green LED is lit. The
slow charging starts and the battery charger supplies an impulsive current (mean
value: 150 mA for BCU6-750; 230 mA for BCU2-1500 and BCU2-1500/B). This
current optimizes the charging process and it is provided for sixteen hours, even if
in ordinary working conditions the battery reaches its full charging level after a
fraction of this time. After sixteen hours the battery charger switches automatically
to the maintenance mode: a minimum current of about 70 mA is provided to the
battery in order to compensate for the auto-discharging of the cells and thus
maintaining the charging level previously achieved.
The battery charger is also able to recognize already fully charged batteries. In fact
fully charged batteries, if submitted to further fast charging, show a remarkable
voltage increase at their terminals. If the charging control detects a voltage
increase exceeding a predetermined threshold level, the battery is considered
charged.
3.2.1
BCU2-1500, BCU2-1500/B and BCU6-750 technical description
The technical description is relative to the BCU2-1500, BCU2-1500/B and BCU6-
750 battery charger models as well as the block diagram shown in fig. 3.8.
The three battery charger models are supplied by means of the following voltage
values:
•
230 V (BCU2-1500);
•
230 V/115 V chosen by a switch (BCU2-1500/B and BCU6-750).
