How to check whether the battery is fully charged?

Multimeter playing in 5 V or 10 V block is best, because more requirements, measuring gear measured value accuracy is higher, the closer the rating of the battery voltage is 4 V dc, if the value is to be measured at around 3.7 V means the battery is normal, because the factory is in the production of mobile phone battery charger no-load voltage of standards is 4 V dc output voltage. Ordinary household batteries no. 1, 2, 5 and 7 all have a voltage of 1.5v. The measured value of the new battery is 1.6v at no load and 1.5v after load is normal.

1. Fixed capacitor detection: detect small capacitors below 10pF

Due to the small capacity of fixed capacitors below 10pF, the multimeter can only be used for measurement. The only way is to qualitatively check whether there is leakage, internal short circuit or breakdown. When measuring, can choose multimeter R 10k block, with two table pen

The resistance of the two pins to any capacitance shall be infinite. If the measured resistance value (pointer swing to the right) is zero, it indicates capacitor leakage damage or internal breakdown.

Detection of 10PF ~ 0.01 F fixed capacitor charging phenomenon, and then judge its good or bad. The multimeter adopts R 1k block. Both transistors have values of more than 100 and have a low penetrating current. 3DG6 and other types of silicon triode can be used to form composite tube. The red and black pen of the multimeter are respectively connected with the emitter e and collector c of the composite tube. Due to the amplification of the compound triode, the process of charge and discharge of the capacitance under test is amplified to make the pointer of the multimeter swing larger for easy observation. It should be noted that: in the test operation, especially in the measurement of small capacitance capacitance, to repeatedly replace the test capacitance pin contact A, B two points, in order to clearly see the multimeter pointer swing. For fixed capacitance above 0.01 F, the R 10k block of the multimeter can be used to directly test whether the capacitor has charging process and whether there is internal short circuit or leakage, and the capacity of the capacitor can be estimated according to the amplitude of the pointer swinging to the right.

If the charge voltage is 4.2v, it is ok; if the battery life is 0.7 times longer than the new battery, it means the battery is ok; if the charge voltage is higher than 4.2v, it means the charger has a problem (note that the voltmeter must be accurate). Please see the following introduction.

1. The nominal voltage of lithium ion battery is 3.7v (3.6v), and the cut-off voltage of charging is 4.2v (4.1v, which is designed differently according to the cell brand). (the specification for lithium ion cells says: lithium ion secondary battery)

2, requirements for lithium ion batteries (GB/T182872000 specification) : first of all, constant current charging, namely must be current, and battery voltage with the charging process gradually increases, when the battery voltage of 4.2 V, 4.1 V), constant voltage charging, instead of constant current charging for the voltage must be current depending on the degree of saturation batteries, as the charging process continue to gradually reduce, when reduced to 0.01 C, think charging termination. (C is a representation of the nominal capacity of the battery in comparison with the current. For example, if the battery has a capacity of 1000mAh, 1C is the charging current of 1000mA, and 0.01C is 10mA.) Of course, the canonical representation is 0.01C5A, which I've simplified here.

3. Why it is considered that 0.01C is the end of charging: this is stipulated by the national standard GB/ t18287-2000, and it is also discussed. In the past, it was common to end with 20mA, which was also stipulated in the industry standard YD/ t998-1999 of the ministry of posts and telecommunications, that is, no matter how big the battery capacity is, the stop current is 20mA. The national standard of 0.01C is conducive to more full charging, which is favorable for the manufacturers to pass the appraisal. In addition, the national standard stipulates that the charging time shall not exceed 8 hours, that is, even if it has not reached 0.01C,8 hours will be considered as the end of charging. (batteries with good quality should reach 0.01C within 8 hours; batteries with poor quality are meaningless to wait)

6. Since there is a protection plate in the battery, can we rest assured? No, because the cut-off parameter of the protection plate is 4.35v (which is still good, but the difference is 4.4v to 4.5v), the protection plate should be prepared in case that the battery will soon decay if it is overcharged every time.

7. What is the appropriate charging current: in theory, the smaller the current, the better for the battery. But you can't wait three days to charge a battery. According to the national standard, the low rate charging is 0.2c (arbitration charging system). If the 1000mAh capacity battery above is taken as an example, that is, 200mA, then we can estimate that this battery can be fully charged in more than 5 hours. (capacity mAh = current mA time h)

The lithium capacity identified by the national technical supervision department is charged at a high rate of 1C and discharged at a low rate of 0.2c. The capacity value is calculated in terms of time. The number of tests is 5, and one of them reaches the end of the test. (there are 5 opportunities, if the first test is qualified, the next 4 times will not be done) a pre-cycle is allowed before the test, that is, charging with 1C constant current to 4.2v will stop, and there is no process of constant voltage to 0.01C in the back, not to mention 14 hours.

8. What charging current a lithium-ion battery can withstand:

1. Charging rate (c-rate)

C is the first letter of Capacity and is used to represent the value of the current during charging and discharging.

For example, when the rated capacity of rechargeable battery is 1100mAh, it means that the discharge time can last for 1 hour with 1100mAh (1C); if the discharge time can last for 5 hours with 200mA (0.2c), the charging can also be calculated according to this comparison.

2. Cut-off voltage (cut-off voltage evoltage)

When a battery is discharging, the voltage drops to the lowest operating voltage at which the battery is no longer suitable for further discharge.

According to different battery types and different discharge conditions, the requirements for the capacity and life of the battery are also different, so the prescribed termination voltage of the battery discharge is also different.

Teach you how to use a multimeter to determine the quality of rechargeable batteries

3, open circuit voltage (OpencircuitvoltageOCV)

When the battery does not discharge, the potential difference between the battery poles is called the open circuit voltage.

The open-circuit voltage of the battery will vary according to the material of the positive and negative electrodes of the battery and the electrolyte. If the material of the positive and negative electrodes of the battery is exactly the same, the open-circuit voltage will be the same regardless of the size of the battery and the change of the geometric structure.

4. Discharge depth (DepthofdischargeDOD)

In the course of using the battery, the percentage of the capacity released by the battery to its rated capacity is called discharge depth.

The discharge depth is closely related to the charging life of the secondary battery. The deeper the discharge depth of the secondary battery is, the shorter its charging life will be. Therefore, deep discharge should be avoided as far as possible.

5. Overdischarge

If the battery in the process of discharge, over the battery discharge of the termination voltage value, also continue to discharge may cause the battery voltage rise, positive and negative active material reversible damage, so that the capacity of the battery significantly reduced.

6. Overcharge

During charging, if the battery continues to be charged after reaching the full state, it may lead to the increase of internal pressure, battery deformation, night leakage and other situations, and the battery performance will be significantly reduced and damaged.

The page contains the contents of the machine translation.