Advanced features 23
Figure 11 shows the actual performance of typical Li ion, NiMH, and NiCd handset battery
packs with a dynamic load, shown in Figure 12, simulating a GSM handset during transmission.
The pulse minimum voltage is the voltage at the battery terminals during the transmit, or high
current portion, of the data frame. The average battery voltage is the voltage across the terminals
measured with a 6∫ digit DMM at approximately 50 readings per second. The figure shows the
pulse minimum voltage reaches the shutdown threshold of 5.7V before the average battery
voltage. The difference between the pulse minimum and average battery voltage also varies as a
function of the electronic resistance with time. Figure 13 shows the variations for specific
battery packs and ranges between 200 and 500mV. The results of these measurements prove that
the impedance of the battery must be considered when evaluating handset performance,
especially near the end of life for the battery pack.
Figure 11
Actual battery pack terminal voltage during GSM phone simulation
NOTE Figure 11 shows the average and minimum battery pack terminal voltage during a
load pulse from a dynamic load simulating a GSM phone.
5.00
5.50
6.00
6.50
7.00
7.50
8.00
8.50
9.00
0.0 2.0 4.0 6.0 8.0 10.0
Battery Voltage, V
Time, hrs
6.59
7.18
8.15
5.7V
Li ion Average Battery Voltage
NiMH Average Battery Voltage
NiCd Average Battery Voltage
Li ion Battery Pulse Minimum Voltage
NiMH Battery Pulse Minimum Voltage
NiCd Battery Pulse Minimum Voltage
6
4
4
1
1
3
5
2
2
5
3
6
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