Keysight N9912A User Manual page 195

The protective functions can be divided between two categories: active and passive.
Active protection refers to the type of protection that depends on at least two or
more protection devices working together to enable the protection Passive
protection refers to the type of protection that is always enabled independent of any
other protection device.
Active Protection
Primary Overcharge Voltage: This prevents the battery from being charged if the
voltage across any cell exceeds approximately 4.35 V per cell. Once the overcharge
protection is tripped, the voltage across each cell must drop below approximately
4.15 V to reset the protection and permit charging.
Secondary Overcharge Voltage: This is a one-time, permanent protection that is
triggered when the voltage across any cell exceeds approximately 4.45 V. Once this
protection is tripped, the battery can no longer be used and must be replaced.
Overdischarge Voltage: This prevents the battery from discharging if the voltage
across any cell drops below approximately 2.6 V. Once the overdischarge voltage
protection is tripped, the voltage across each cell must be charged to approximately
3 V to reset the protection and permit discharging.
Primary Overcharge Current: This prevents the battery from being charged if the
average charging current reaches or exceeds 3.5A for a time period of 120 seconds
or more.
Secondary Overcharge Current: This prevents the battery from being charged if the
charging current reaches or exceeds 4A+/–20% for a time period of 20 milliseconds
or more.
Primary Overdischarge Current: This prevents the battery from being discharged if
the average current out of the battery reaches or exceeds 5A for a time period of 120
seconds or more. This protection can be reset by removing the load.
Secondary Overdischarge Current: This prevents the battery from being discharged if
the current out of the battery reaches or exceeds 6A for a time period of 20
milliseconds or more. This protection can be reset by removing the load.
Short Circuit Protection: This prevents the battery from being charged or discharged
and protects against damage or lost data if the current in or out of the battery
reaches or exceeds 12.5A for a time period of 183 microseconds or more. This
protection can be reset by removing the load.
Overtemperature Charging: The system microcontroller prevents the battery from
being charged if the cell temperature exceeds 46C. Once the overtemperature
charging protection is tripped, the cell temperature has to drop to or below 45C to
reset the protection and permit charging.
Overtemperature Discharging: The system microcontroller prevents the battery from
being discharged if the cell temperature exceeds 65C. 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: A PTC(positive temperature coefficient) polyfuse in series
between the Li-ion cells and the charging and discharging transistors will open up
and limit current flow to the battery terminals as a function of very high
temperatures. This protection is resettable once the overstress condition is removed.
The maximum operating temperature of this fuse is 85C.
Safety Considerations 195