Keithley 2461 Reference Manual page 353

Model 2461 Interactive SourceMeter® Instrument Reference Manual Section 4: Source-measure considerations
Charging
A battery is usually charged using a constant current. To do this, use a Model 2461 as a voltage
source set to the voltage rating of the battery, with the target charging current set as the current limit.
At the start of the test, the battery voltage is less than the voltage output setting of the Model 2461.
As a result, this voltage difference drives a current that is immediately limited to the user-defined
current limit. When in current limit, the Model 2461 acts as a constant current source until it reaches
the programmed voltage level. As the battery becomes fully charged, the current decreases until it
reaches zero or near zero. To prevent safety hazards or damage to the battery, be careful not to
overcharge the battery.
Discharging
When discharging a battery, the Model 2461 operates as a sink because it is dissipating power
instead of sourcing it. The voltage source of the Model 2461 is set to a lower level than the battery
voltage. The current limit sets the discharge rate. When the output is enabled, the current from the
battery flows into the HI terminal of the Model 2461. As a result, the current readings are negative.
The discharge current should stay constant until the battery voltage decreases to the voltage source
setting of the Model 2461.
If you are using the current source to charge or discharge batteries, the following precautions must
be observed. Failure to observe these precautions could result in instrument damage that is not
covered by the warranty.
Make sure the external voltage never exceeds the voltage limit setting of the current source. This will
cause excessive current to be drawn from the external battery or source.
Be sure to set the output-off state of the current source for high impedance. This setting opens the
output relay when the output is turned off. With the normal output-off state selected, turning the
output off sets the voltage limit to zero. This 0 V source limit condition will cause excessive current to
be drawn from the external battery or source.
Carefully consider and configure the output-off state, source, and limits before connecting the Model
2461 to a device that can deliver energy. Devices that can deliver energy include voltage sources,
batteries, capacitors, and solar cells. Configure instrument settings before making connections to the
device. Failure to consider the output-off state, source, and limits may result in damage to the
instrument or to the device under test (DUT).
When using the current source as a sink, always set the voltage limit and configure overvoltage
protection (OVP) to levels that are higher than the external voltage level. Failure to do so could result
in excessive current flow into the Model 2461 (> 100 mA) and incorrect measurements.
2461-901-01 A/November 2015 4-17