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Safety Considerations
Battery Protective Functions
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.
Overd ischarge 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 Overd ischarge 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 Overd ischarge 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.
21- 8
Keysight N9912-90001 User's Guide
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