li-ioncharge - OVERCHARGE/OVERDISCHARGE/OVERCURRENT SAFETY...

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Unformatted text preview: OVERCHARGE/OVERDISCHARGE/OVERCURRENT SAFETY CIRCUITS • The Functions of the Safety Circuits (Typical Functions) The voltages listed below are typical values and are not guaranteed. The charge voltage varies according to model number. 1. The Overcharge Safety Function The charge stops when the voltage per cell rises above 4.30 ± 0.05 V. The charge restarts when the voltage per cell falls below 4.00 ± 0.15 V. 2. The Overdischarge Safety Function The discharge stops when the voltage per cell falls below 2.3 ± 0.1 V. The discharge restarts when the voltage per cell rises above 3.0 ± 0.15 V. 3. The Overcurrent Safety Function The discharge is stopped when the output terminals are shorted. The discharge restarts when the short is removed. • Reference Example of the Safety Circuits Battery Pack Unusable Region 4.3V 4.2V Charge Batteries Safety Circuits Region Used by the Set Charger Discharge 3.0V 2.3V Overdischarge Region Unusable Region • The safety circuits in the diagram above are for overcharging, overdischarging, and overcurrent for a single cell battery pack. Please contact Panasonic when two or more cells are connected or when actually using this or other circuits. LITHIUM ION JANUARY 2000 This information is generally descriptive only and is not intended to make or imply any representation, guarantee or warranty with respect to any cells and batteries. Cell and battery designs/specifications are subject to modification without notice. Contact Panasonic for the latest information. OVERCHARGE/OVERDISCHARGE/OVERCURRENT SAFETY CIRCUITS - CONTINUED • Battery Pack Block Diagram (Reference Example) The diagram below shows a diagram of a lithium ion battery pack. The battery pack includes the batteries, the safety circuits, and thermistors. 1. The Safety Circuits 1.1 The Controller IC The controller IC measures the voltage for each cell (or for each parallel battery block) and shuts off a control switch to either prevent overcharging (if the voltage exceeds the specified voltage range) or to prevent overdischarging (if the voltage falls below the specified voltage range). Moreover, the voltage of the control switch is measured on both ends and in order to prevent overcurrent, both control switches are shut off if the voltage exceeds specifications. 1.2 The Control Switches The control switches usually comprise FET structures, and they turn off the charge or discharge depending on the output of the controller IC. 1.3 The Temperature Fuse (Reference Materials) If the control switches experience abnormal heating, this fuse cuts off the current (non-restoring). 2. The Thermistors The thermistors are included in order to accurately measure the battery temperature within the lithium ion battery packs. The battery or charger measures the resistance value of the thermistor between the Tterminal and the negative terminal and during the charging process, controls the charge current along with controlling until the charge is terminated. + Battery Pack Safety Circuits Controller IC T - • • Thermistor Temperature Fuse Control SW Control SW The battery pack must be equipped with a noise filter at the voltage detectors in the block diagram above to insure that outside noise does not cause the battery to malfunction. Please check against the final product. Please include a total charge timer and a charge completion timer on the charging circuit in order to provide redundant safety control. LITHIUM ION JANUARY 2000 This information is generally descriptive only and is not intended to make or imply any representation, guarantee or warranty with respect to any cells and batteries. Cell and battery designs/specifications are subject to modification without notice. Contact Panasonic for the latest information. HOW TO CHARGE THE BATTERIES We recommend the following charging process to insure the optimal performance of the lithium ion battery. • Applicable Battery Packs The discussion below assumes that the battery packs are equipped with internal safety circuits to prevent overcharging and overdischarging, and assumes that the battery is a single cell battery. • Charging Method The lithium ion battery can be charged by the constant voltage/constant current charging method found in the “Notes and Precautions” at the beginning of this document. (See page 2, “Notes and Precautions”) • Functions and Performance Required in the Charger (Recommendations) (1) Charge Voltage The voltage between the charging terminals should be no more than 4.20 V (Set this at 4.20 V (max) after taking into account fluctuations in power supply voltages, temperature deviations, etc.). The charge voltage varies according to model number. For example, please charge CGP30486 at 4.10 volt. (2) Charge Current The reference charge current should be 0.7 CmA. (3) Ambient Temperature of the Battery Pack During Charge 0°C to 45°C (Consult Panasonic if the battery pack is to be used outside of this temperature range). (4) Low-Voltage Battery Pack Charge When the voltage per cell is 2.9 V or less, charge using a charge current of 0.1 CmA or less. (5) Termination of Charging The system will determine that the battery is full by detecting the charge current. Stop charging once the current has reached 0.1 CmA to 0.07 CmA. Note that there will be some degree of variation for each individual battery. (6) Charge Timer A total charge timer and a charge completion timer should be included. (7) Countermeasures for Battery Problems Select an overvoltage guard in the power supply so that there will be no excessive voltage applied to the battery even if there is a problem with the power supply. • The discussion above assumes a single cell battery. If two or more cells will be used or if there are other situations, please consult with Panasonic. LITHIUM ION JANUARY 2000 This information is generally descriptive only and is not intended to make or imply any representation, guarantee or warranty with respect to any cells and batteries. Cell and battery designs/specifications are subject to modification without notice. Contact Panasonic for the latest information. FLOWCHART FOR CHARGING LITHIUM ION BATTERY PACKS Lithium Ion Battery Pack Charge Flowchart (Example) Reference example of charging a single-cell lithium ion battery pack OCV: Battery pack load open voltage START T1 tmin Battery pack insertion check tbat NO tmax Is the battery pack CV inserted? ichg YES A iset1 iset2 T2 Charge total timer count T1 T3 YES : Charge total timer count : Low temperature threshold setting value : Battery temperature : High temperature threshold setting value : Constant voltage : Charge current : Electrical current set value : Electrical current set value : Charge complete timer count : Recharge timer count Total timer end decision T1 > 720 minutes Battery temperature check tmin<tbat<tmax NO Wait A YES Is voltage check 1 (no load) higher than the charge completion voltage? 4.1 V or 4.2 V NO OCV<4.1V YES Voltage check 2 (no load) OCV>2.9V NO YES 0.7 CmA charge A NO 0.1 CmA charge CV mode post-transition Overdischarge check charge current check Enter into CV OCV voltage > 3V A ichg < iset1 YES YES Charge complete timer count T2 NO Charge complete timer end decision T2 < 120 minutes NO Re-charge timer count T3 Re-charge timer end decision T3 < 120 minutes YES YES A NO Charge stop current check A NO ichg<iset 2 YES Timeout error Overcharge error Charge complete LITHIUM ION JANUARY 2000 This information is generally descriptive only and is not intended to make or imply any representation, guarantee or warranty with respect to any cells and batteries. Cell and battery designs/specifications are subject to modification without notice. Contact Panasonic for the latest information. ...
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