Battery Common Issues and Analysis

Battery Common Issues and Analysis

1. What is overcharging, and what impact does it have on battery performance?

 

Overcharging refers to the act of continuing to charge a battery after it has been fully charged. For Ni-MH batteries, overcharging leads to the following reactions:

 

Cathode: 4OH-- 4e → 2H2O + O2↑; ①

 

Anode: 2H2 + O2 → 2H2O ②

 

Since the anode capacity is designed to be higher than the cathode capacity, the oxygen produced at the cathode diffuses through the separator and reacts with the hydrogen produced at the anode. Under normal circumstances, the internal pressure of the battery does not increase significantly. However, if the charging current is too high or the charging time is too long, the oxygen produced may not be consumed in time, leading to increased internal pressure, battery deformation, leakage, and other adverse phenomena. At the same time, its electrical performance will also decrease significantly.

 

For lithium-ion batteries, overcharging leads to the following reactions:

 

Oxygen production: 3CoO2 → Co3O4 + O2↑;

 

Solvent oxidation: ROCO2R + 3O2 → 3CO2 + 3HO2↑;

 

Solvent and water reaction: ROCO2R + HO2 → 3ROH + 3CO2↑;

 

Salt and water reaction: LiPF6 + HO2 → 2HF + LiF + POF3; etc.

 

2. What is overdischarging, and what impact does it have on battery performance?

 

When a battery discharges all the stored electricity and the voltage reaches a certain value, continuing to discharge will cause overdischarge. The discharge cut-off voltage is usually determined based on the discharge current, with 0.2C-2C discharge generally set at 1.0V per cell, and 3C or above, such as 5C or 10C discharge, set at 0.8V per cell. Overdischarge can have disastrous consequences for the battery, especially large current overdischarge or repeated overdischarge, which has a greater impact on the battery. Generally speaking, overdischarge will cause an increase in internal pressure, and the reversibility of the active materials at the positive and negative electrodes will be damaged. Even after charging, only a partial recovery is possible, and the capacity will also decline significantly.

 

3. What are the main causes of battery swelling?

 

01) Poor battery protection circuit;

 

02) Battery without protection function causing cell swelling;

 

03) Poor charger performance, excessive charging current causing battery swelling;

 

04) Battery subjected to high rate, large current continuous overcharging;

 

05) Battery forced overdischarge;

 

06) Cell internal absorption (for lithium-ion batteries).

 

4. What is battery explosion? How to prevent battery explosion?

 

Any part of the solid material inside the battery is expelled instantaneously to a distance more than 25cm away from the battery, which is called an explosion. General prevention measures include:

 

01) Avoid overcharging and short-circuiting;

 

02) Use good charging equipment for charging;

 

03) The battery's vent hole must always be kept unobstructed;

 

04) Pay attention to heat dissipation when using the battery;

 

05) Prohibit the use of different types and different ages of batteries together.

 

5. What are the types of battery protection components and their respective advantages and disadvantages?

 

The following table compares the performance of several common battery protection components:

Name	Main Material	Function	Advantages	Disadvantages
Thermal Switch	PTC	Protection for large current in battery packs	Rapidly senses changes in current and temperature in the circuit. When the temperature is too high or the current is excessive, it causes the bimetallic strip inside the switch to reach the rated value, causing the metal strip to jump off and protect the battery and electrical appliances.	The metal strip may not reset after jumping off, causing the battery pack voltage to fail to work.
Overcurrent Protector	PTC	Protection for excessive current in battery packs	This device's resistance increases linearly with temperature. When the current or temperature rises to a certain value, the resistance changes dramatically (increases), reducing the current to the mA level. When the temperature drops, it returns to normal and can be used as a battery connection strip inserted into the battery pack.	Higher price
Fuse	FUSE	Sensing circuit current and temperature	When the current in the circuit exceeds the rated value or the battery temperature rises to a certain value, the fuse melts to break the circuit, protecting the battery pack and electrical appliances from damage.	The fuse cannot be restored after melting and needs to be replaced in time, which is more troublesome.

 

6. What is a portable battery?

 

Portable means easy to carry and convenient to use. Portable batteries mainly provide power for handheld, cordless devices. Larger batteries (e.g., 4 kg or more) do not belong to portable batteries. Today's typical portable batteries weigh about a few hundred grams.

 

The family of portable batteries includes primary batteries and rechargeable batteries (secondary batteries). Button cells are a special group among them.

 
7. What are the characteristics of rechargeable portable batteries?

 

Each battery is an energy converter. It can directly convert stored chemical energy into electrical energy. For rechargeable batteries, this process can be described as follows: Charging process - electrical energy is converted into chemical energy → chemical energy is converted into electrical energy during the discharge process → electrical energy is converted into chemical energy. Secondary batteries can cycle more than 1000 times.

 

There are rechargeable portable batteries in different electrochemical types, including lead-acid type (2V per cell), nickel-cadmium type (1.2V per cell), nickel-metal hydride type (1.2V per cell), and lithium-ion batteries (3.6V per cell). The typical characteristics of these batteries are relatively stable discharge voltage (there is a voltage platform during discharge), and the voltage drops rapidly at the beginning and end of discharge.

 

8. Can any charger be used for rechargeable portable batteries?

 

No, because any charger corresponds to a specific charging process and can only correspond to a specific electrochemical process, such as lithium-ion, lead-acid, or Ni-MH batteries. They not only have different voltage characteristics but also different charging modes. Only specially developed fast chargers can achieve the most suitable charging effect for Ni-MH batteries. Slow chargers can be used in emergencies but require more time. It should be particularly noted that although some chargers have qualified labels, caution should be exercised when using them as chargers for batteries of different electrochemical systems. The qualified label only indicates that the device complies with European electrochemical standards or other national standards. This label does not provide any information about which type of battery it is suitable for. Using a cheap charger to charge Ni-MH batteries will not yield satisfactory results and is also dangerous. The same caution should be exercised with chargers for other types of batteries.

 

9. Can rechargeable 1.2V portable batteries replace 1.5V alkaline manganese batteries?

 

Alkaline manganese batteries have a voltage range of 1.5V to 0.9V during discharge, while rechargeable batteries have a constant voltage of 1.2V per cell during discharge. This voltage is roughly equal to the average voltage of alkaline manganese batteries, so it is feasible to replace alkaline manganese batteries with rechargeable batteries, and vice versa.

 

10. What are the advantages and disadvantages of rechargeable batteries?

 

The advantage of rechargeable batteries is their long service life. Although they are more expensive than primary batteries, they are economical and cost-effective from a long-term perspective. Moreover, the load capacity of rechargeable batteries is higher than that of most primary batteries. However, the discharge voltage of ordinary secondary batteries is basically constant, making it difficult to predict when the discharge will end, causing some inconvenience during use. But lithium-ion batteries can provide longer usage time for camera equipment, high load capacity, high energy density, and the voltage drop decreases as the discharge progresses.

 

11. What are the advantages of nickel-metal hydride batteries? What are the advantages of lithium-ion batteries?

 

The advantages of nickel-metal hydride batteries are:

 

01) Low cost;

 

02) Good fast charging performance;

 

03) Long cycle life;

 

04) No memory effect;

 

05) Pollution-free, green battery;

 

06) Wide temperature range for use;

 

07) Good safety performance.

 

The advantages of lithium-ion batteries are:

 

01) High energy density;

 

02) High working voltage;

 

03) No memory effect;

 

04) Long cycle life;

 

05) Pollution-free;

 

06) Lightweight;

 

07) Low self-discharge.

 

12. What are the advantages of lithium iron phosphate batteries?

 

The main application direction of lithium iron phosphate batteries is power batteries, and their advantages are mainly reflected in the following aspects:

 

01) Extra-long life;

 

02) Safe to use;

 

03) Can be charged and discharged quickly with large currents;

 

04) High-temperature resistance;

 

05) Large capacity;

 

06) No memory effect;

 

07) Small size, lightweight;

 

08) Green and environmentally friendly.

 

13. What are the advantages of lithium polymer batteries?

 

01) No battery leakage problem, the battery contains no liquid electrolyte, using a gel-like solid;

 

02) Can be made into thin batteries: with a capacity of 3.6V, 400mAh, the thickness can be as thin as 0.5mm;

03) The battery can be designed into various shapes;

 

04) The battery can be bent and deformed: polymer batteries can be bent up to about 90 degrees;

 

05) Can be made into multi-layer combinations within a single cell to achieve high voltage;

 

06) The capacity will be higher than that of lithium-ion batteries of the same size.

 

14. What is the principle of chargers? What are the main types?

 

Chargers are static power conversion devices that use power electronic semiconductor devices to convert fixed voltage and frequency alternating current into direct current. There are many types of chargers, such as lead-acid battery chargers, valve-regulated lead-acid battery testers and monitors, nickel-cadmium battery chargers, nickel-metal hydride battery chargers, lithium-ion battery chargers, portable electronic device lithium-ion battery chargers, lithium-ion battery protection circuit multifunctional chargers, electric vehicle battery chargers, etc.