|NI-DCPower (English | Japanese)|
As non-ideal voltage sources, batteries have internal series resistance. This internal resistance varies based on the chemistry used for different battery types. The internal resistance can be affected by a number of variables including how the battery is used, level of charge, and age.
Internal resistance causes a battery's voltage to drop as higher currents are drawn. As the current increases, so does the internal voltage drop due to Ohm's Law (V=I×R). This causes the voltage at a battery's terminals to decrease as the current increases.
If the internal resistance and the current drawn from a battery are high enough, the output voltage can drop significantly, regardless of how much charge it is holding. For battery-operated devices, if the voltage drops below a certain threshold it causes the device to shut down. This demonstrates the large role internal resistance can play when testing battery-operated products.
You can program channel 0 of the NI PXIe-4154 to vary the output resistance from -40 mΩ to 1 Ω. The positive range of the output resistance allows the channel to emulate the internal resistance of a battery over its lifetime. The negative resistance range allows you to compensate for voltage drops due to resistive losses between the remote sense points and the DUT terminals.