What are the core indicators and parameters of rechargeable batteries?
Rechargeable batteries are rechargeable batteries with a limited number of recharges and are used with chargers. No. 5 and No. 7 are generally sold in the market, but there is also No. 1. The advantages of rechargeable batteries are economic, environmental protection, sufficient power, suitable for high-power, long-term use of electrical appliances (such as Walkman, electric toys, etc.). The voltage of the rechargeable battery is lower than that of the same type of disposable battery. The AA battery (Charge 5) is 1.2 volts, and the 9V rechargeable battery is actually 8.4 volts. Now the general charging times can be around 1000 times.
Core indicators of rechargeable batteries
1. Safety performance
Batteries with unsatisfactory safety performance indexes are impossible to accept. Among them, the biggest impact is explosion and liquid leakage. The occurrence of explosion and liquid leakage is mainly related to the internal pressure, structure and process design of the battery (such as failure of safety valve, no protection circuit for lithium ion battery, etc.) and improper operation that is prohibited (such as putting the battery into fire).
2. Capacity
Refers to the total amount of electricity that the battery can discharge under certain discharge conditions. According to the IEC standard and the national standard, the nickel-cadmium and nickel-metal hydride batteries are charged at 0.1C for 16 hours and discharged at 0.2C to 1.0V at 20 ± 50C for the rated capacity of the battery, expressed in C; lithium ion The battery is charged at room temperature, constant current (1C), and constant voltage (4.2V) for 3 hours, and then discharged at 0.2C to 2.75V as the rated capacity of the battery. The unit of battery capacity is mah and Ah (1Ah = 1000mAh).
Take AA2300mAh Ni-MH rechargeable battery as an example, which means that the battery is charged at 230mA (0.1C) for 16 hours and then charged at 460mA (0.2C)
When discharged to 1.0V, the total discharge time is 5 hours, and the discharged electricity is 2300mAah. Correspondingly, if the current is discharged at 230 mA, the discharge time is about 10 hours.
3. internal resistance
The internal resistance of the battery refers to the resistance to the current when it flows through the battery. The internal resistance of the rechargeable battery is very small, and it requires a special instrument to measure more accurate results. The internal resistance of the battery is generally known as the internal resistance of the charged state, even when the battery is fully charged (corresponding to the internal resistance of the discharge state, which refers to the internal resistance of the battery after fully discharged. The internal resistance in the charged state is large and not very stable). The greater the internal resistance of the battery, the more energy the battery consumes itself, and the lower the efficiency of the battery. A battery with a large internal resistance heats up greatly during charging, causing the temperature of the battery to rise sharply. The impact on the battery and charger are great. As the number of times the battery is used increases, the internal resistance of the battery will increase to varying degrees due to the consumption of the electrolyte and the decrease in the activity of the chemical substances inside the battery. The lower the quality of the battery rises faster.
4. Cycle life
Cycle life is the number of repeated charging and discharging that the battery can undergo. The battery life and capacity are in an inverse relationship. The cycle life of a general nickel-metal hydride battery can reach more than 500 times. The life of high-capacity batteries is shorter, but it can also reach more than 200 times. The cycle life is also closely related to the charging and discharging conditions. Generally, the larger the charging current (the faster the charging speed), the shorter the cycle life.
5. Charge retention ability
Charge retention capacity, usually referred to as self-discharge, refers to the retention capacity of the battery in a certain environmental condition under the open circuit state. Self-discharge is mainly determined by many factors such as battery material, manufacturing process, storage conditions and so on. Generally, the higher the temperature, the greater the self-discharge rate. A certain degree of self-discharge of rechargeable batteries is normal. Taking nickel-metal hydride battery as an example, the IEC standard stipulates that after the battery is fully charged, it should be left open for 28 days at a temperature of 20 ± 5 ° C and a humidity of 65 ± 20%. Greater than 60%). The self-discharge of lithium-ion batteries and dry batteries is much smaller.
Rechargeable battery parameters
1. Energy density
The electric energy capacity contained in unit volume or unit weight, for the same power requirements, batteries with high energy density can be smaller in size and lighter in weight.
2, C current
Refers to the amount of current that a fully charged battery is discharged or an exhausted battery is fully charged within an hour. In fact, it is the numerical value of the ampere-hour capacity. For 1800mA. Capacity batteries, the C current is 1800mA. For a 2000mA. Capacity battery, the C current is 2000mA.
3. Open circuit voltage
Refers to the potential difference between the two terminals of the battery.
The new battery has fine grains of electrode material, which can obtain the largest electrode surface area. Due to use, the contents of the battery are crystallized. After the crystallization is formed, the crystal grains increase, also known as (passivation), which reduces the available electrode area, and the grown crystal grains will cause an increase in self-discharge and make the battery Reduced capacity and impaired performance. This is the memory effect. The reason for the memory effect is due to incomplete partial charging and discharging of the battery.
5. Self-discharge rate
The charged battery will gradually lose its power even when it is not in use. Generally, the higher the temperature, the more significant the self-discharge.
If you want to know more, our website has product specifications for batteries, you can go to ALLICDATA ELECTRONICS LIMITED to get more information