26
Advanced features
Two methods are used to determine the impedance value of the cell or battery pack. The first
method uses data from the battery manufacturer or another source and is simply entered into the
Model 2306 from the front panel or over the GPIB bus. The second method involves a simple
series of measurements as follows.
Figure 14
Voltage drop sample (with supplied Li ion battery pack)
NOTE
Figure 14 shows the voltage drop during the transmit portion of the pulse with the
supplied Li ion battery pack. See Figure 15 for the comparative illustration using the
Model 2306.
Figure 14 shows the transient voltage response at the battery terminals with the handset bat-
tery. Using Figure 14, the voltage drop during the transmit portion of the pulse of a GSM phone
with the supplied Li ion battery is 0.348V. Using the pulse current mode of the battery channel
the measured current during the transmit portion of the data frame is I
H
= 1.536A and the idle
portion of the data frame is I
L
= 0.082A. To estimate R
i
from the measured voltage, we use
:
VH – VL = 0.348 V
R
i
V
H
V
L
–
I
H
I
L
–
--------------------
0.348
V
1.454
A
------------------
0.239
Ω
=
=
≅