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1.12 BATTERY CHARGER INFORMATION
1.12.1 GENERAL
The battery pack for the 7243 portable contains
six nickel metal hydride (NiMH) batteries connected
in series. Nominal battery pack voltage is 7.5 volts and
battery capacity is 1450 mAH.
The 7243 charger shown in Figure 1-1 has two
slots in which to place a battery. The back slot is for
fast charging and the front slot is for slow charging.
Only the battery can be inserted in the fast charge slot
and the entire transceiver can be inserted in the slow
charge slot if desired. Batteries can be charged in both
slots at the same time. The operation of the LEDs is
shown in Table 1-2.
Fast Charge Slot
Fast Charge Slot
Indicator
Figure 1-1 Battery Charger
1.12.2 FAST CHARGING
When a battery is placed in the fast charge slot,
the fast charge indicator briefly flashes red while the
battery is checked to determine if its temperature is
within the required range (0 to +45° C/+32 to +113°F).
If it is, fast charging begins and it changes to steady
red. The fast charge rate is 1320 mA ±100 mA. When
the battery is nearly fully charged, it switches to the
trickle rate of 20-40 mA and the indicator turns green.
It continues at the trickle rate until the battery is
removed from the charger. Approximate charge time
in this slot for a fully discharged battery is 1.5 hours.
Slow Charge Slot
Slow Charge Slot Indicator
Table 1-2 Charger Indicators
Indication
Fast Charge
Flashing Red [1] Checking battery
condition
Constant Red
Rapid charge mode
Constant Green Trickle charge mode Slow charge mode
Off [2]
No charging is
occurring
[1] If condition persists, battery temperature may not within
required range (0 to +45° C).
[2] Possible causes are poor contact (clean the charger and
battery contacts) or a defective battery.
The charger uses the ∆T/∆t (change in tempera-
ture/change in time) method to sense that the battery is
nearly fully charged and that switching to the trickle
mode should occur. This method detects when the
battery temperature begins increasing at a faster rate
which normally provides the first indication that the
battery is fully charged.
To provide fail-safe operation, the trickle rate is
also selected if the battery temperature rises above
+50° C (+122° F) or charge time in the rapid mode
exceeds 90 minutes ±20%.
NOTE: Occasionally, a fully charged condition may be
falsely detected and the trickle mode entered after only
a few minutes of rapid charging. To resume normal
rapid charging if this occurs, momentarily lift the
battery out of the slot.
1.12.3 SLOW CHARGING
Batteries charged in the front slot are always
charged at the slow rate of 100-120 mA. The slow
charge indicator turns green when charging is occur-
ring. Typical charge time in this slot for a fully
discharged battery is 20 hours (with transceiver power
turned off if applicable). If the transceiver power is on,
this slot basically maintains the charge of the battery.
1-4
GENERAL INFORMATION
Indicator
Slow Charge
N/A
N/A
No charging is
occurring
November 2001
Part No. 001-7240-001
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