Keysight N9923-90001 User’s Guide253Safety ConsiderationsBattery Protective FunctionsThe protective functions can be divided between two categories: active andpassive. Active protection refers to the type of protection that depends on atleast two or more protection devices workin g together to enable the protectionPassive protection refers to the type of protection that is always enabledindependent of any other protection device.Active ProtectionPrimary Overcharge Voltage: This prevents the battery from being charged ifthe voltage across any cell exceeds approximately 4.35 V per cell. Once theovercharge protection is tripped, the voltage across each cell must drop belowapproximately 4.15 V to reset the protection and permit charging.Secondary Overcharge Voltage: This is a one-time, permanent protection thatis 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 bereplaced.Overd ischarge Voltage: This prevents the battery from discharging if thevoltage across any cell drops below approximately 2.6 V. Once theoverdischarge voltage protection is tripped, the voltage across each cell mustbe charged to approximately 3 V to reset the protection and permitdischarging.Primary Overcharge Current: This prevents the battery from being charged ifthe average charging current reaches or exceeds 3.5A for a time period of 120seconds or more.Secondary Overcharge Current: This prevents the battery from being chargedif the charging current reaches or exceeds 4A+/–20% for a time period of 20milliseconds or more.Primary Overd ischarge Current: This prevents the battery from beingdischarged if the average cu rrent out of the battery re aches or exceeds 5A for atime period of 120 seconds or more. This protection can be reset by removingthe load.Secondary Overd ischarge Current: This prevents the battery from beingdischarged if the current out of the battery reaches or exceeds 6A for a timeperiod of 20 milliseconds or more. This protection can be reset by removing theload.Short Circuit Protection: This prevents the battery from being charged ordischarged and protects against damage or lost data if the current in or out ofthe battery reaches or exceeds 12.5A for a time period of 183 microseconds ormore. This protection can be reset by removing the load.Overtemperature Charging: The system microcontroller prevents the batteryfrom being charged if the cell temperature exceeds 46C. Once theovertemperature charging protection is tripped, the cell temperature has todrop to or below 45C to reset the protection and permit charging.
