Keysight FieldFox B Series User Manual page 841

Safety Considerations
Battery Protective Functions
Overtemperature Discharging: The system microcontroller prevents the
battery from being discharged if the cell temperature exceeds 67C. Once the
overtemperature discharging protection is tripped, the battery is automatically
shut off which results in turning off the instrument as well.
Passive Protection
Reverse Charging: A reverse protection diode prevents against damage or lost
data due to a reverse charge polarity applied to the battery terminals.
Primary Overtemperature: The maximum operating temperature of this fuse is
85C. An overtemperature cutout permanently opens at 85C with no recovery.
Secondary Overtemperature: A second PTC polyfuse built into each Li-ion cell
will open up and limit current flow at high currents.
Tertiary Overtemperature: A current interrupt device (CID) within each Li-ion
cell will permanently open up when an individual cell's internal pressure is too
high. As each cell fuse is permanently interrupted, overall battery performance
will become severely degraded, up to and including disabling the battery.
Keysight N9938-90006 User's Guide 841