Lithium battery overcharge, overdischarge, short circuit protection circuit details and advantages and types
The battery circuit primarily consists of a lithium battery protection ASIC, the DW01, along with charge and discharge control MOSFETs (including two N-channel MOSFETs). A single lithium cell is connected between B+ and B-, while the battery pack outputs from P+ to P-. During charging, the charger’s output voltage is applied across P+ and P-, allowing current to flow from P+ through B+ and B- of the single cell, then through the charge control MOSFET to P-. If the voltage of a single cell exceeds 4.35V, the OC pin of the DW01 sends a signal to turn off the charge control MOSFET, stopping the charging process immediately and preventing overcharging damage.
During discharging, if the voltage of a single cell drops to 2.30V, the OD pin of the DW01 triggers the discharge control MOSFET to shut off, halting the discharge and avoiding overdischarge. The CS pin of the DW01 serves as a current detection pin; when a short circuit occurs, the conduction voltage drop of the MOSFET increases rapidly, causing the CS pin voltage to rise quickly. This prompts the DW01 to turn off the MOSFET, providing overcurrent or short-circuit protection.
Lithium batteries offer numerous advantages, including high energy density, high operating voltage, no memory effect, long cycle life, no pollution, lightweight design, and low self-discharge. Lithium polymer batteries further enhance these benefits by eliminating liquid electrolytes, allowing for thinner designs, flexible shapes, and higher voltages in a single unit. They also have a higher capacity compared to traditional lithium-ion batteries.
The IEC standard test for lithium batteries involves a 500-cycle charge-discharge test where the capacity must remain above 60% of the initial value. For charge retention testing, the battery is stored at 20±5°C for 28 days after being charged to 4.2V at 1C and discharged at 0.2C. Self-discharge rates vary depending on battery type and environmental conditions, with lithium batteries typically having lower self-discharge than other rechargeable systems.
Internal resistance is a key performance metric, measured using AC methods to avoid polarization effects. Internal pressure tests simulate high-altitude conditions to ensure safety under extreme pressures. Temperature significantly affects battery performance, with optimal operation within a specific range. Overcharging and overdischarging can severely damage batteries, so various control methods like peak voltage, temperature change rate, and time-based controls are used to prevent them.
Using batteries of different capacities together can lead to leakage, zero voltage, or reduced performance due to inconsistent charging and discharging. Battery explosions, defined as solid material being expelled more than 25cm, are tested using nets to ensure safety. In series-connected lithium batteries, individual cell inconsistencies can cause overcharging or overdischarging, highlighting the need for advanced balancing techniques.
Lithium-ion batteries have rated voltages of 3.6V or 3.7V, with termination charges depending on anode materials. Discharge below the recommended voltage leads to overdischarge, which damages the battery. Portable electronics rely heavily on battery advancements, with lithium batteries offering superior energy density, stable voltage, and long storage life. Despite their high cost, they are widely used in devices requiring compact, high-performance power sources.
Non-rechargeable lithium batteries, such as lithium-manganese dioxide and lithium-thionyl chloride, are commonly used in cameras, watches, and medical devices. These batteries have high specific energy, long shelf life, and wide operating temperature ranges. However, they are not rechargeable and require careful handling to avoid damage or safety hazards.
Proper usage includes following manufacturer guidelines, avoiding over-discharge, and using batteries within specified temperature limits. Understanding battery models and ratings ensures compatibility and optimal performance in electronic devices. With ongoing technological improvements, lithium batteries are becoming more affordable and widely adopted in various applications.
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