Specifications

5.11 Battery measurement
The internal resistance of a battery is generally measured using a 1 kHz AC signal. It is not allowed
to directly connect a battery to the auto-balancing bridge type impedance measurement instrument.
If a battery is connected directly, the instrument becomes the DC load, typically 100 Ω for the
battery. The instrument may be damaged by a discharge current flow from the battery. Figure 5-42
shows the recommended setup for this measurement. C
1
and C
2
block DC current from flowing into
the instrument. The value of C
1
should be calculated using the minimum measurement frequency.
For example, when the measurement is made at 1 kHz and above, C
1
should be larger than 32 µF.
The voltage rating of C
1
and C
2
must be higher than the output voltage of the battery.
Note: The Agilent 4338B milliohm meter can measure the internal resistance of a battery up to 40 V
DC directly connected to the measurement terminals because the DC blocking capacitors
have been installed in the 1 kHz bridge circuit.
Figure 5-42. Battery measurement setup
5-31